diff --git a/swh/loader/cli.py b/swh/loader/cli.py
--- a/swh/loader/cli.py
+++ b/swh/loader/cli.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2019-2020 The Software Heritage developers
+# Copyright (C) 2019-2021 The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -48,16 +48,35 @@
     logger.debug(f"registry: {registry_entry}")
     loader_cls = registry_entry["loader"]
     logger.debug(f"loader class: {loader_cls}")
-    return loader_cls(**kwargs)
+    return loader_cls.from_config(**kwargs)
 
 
 @swh_cli_group.group(name="loader", context_settings=CONTEXT_SETTINGS)
+@click.option(
+    "--config-file",
+    "-C",
+    default=None,
+    type=click.Path(exists=True, dir_okay=False,),
+    help="Configuration file.",
+)
 @click.pass_context
-def loader(ctx):
+def loader(ctx, config_file):
     """Loader cli tools
 
     """
-    pass
+    from os import environ
+
+    from swh.core.config import read
+
+    ctx.ensure_object(dict)
+    logger.debug("ctx: %s", ctx)
+
+    if not config_file:
+        config_file = environ.get("SWH_CONFIG_FILENAME")
+
+    ctx.obj["config"] = read(config_file)
+    logger.debug("config_file: %s", config_file)
+    logger.debug("config: ", ctx.obj["config"])
 
 
 @loader.command(name="run", context_settings=CONTEXT_SETTINGS)
@@ -71,6 +90,10 @@
 
     from swh.scheduler.cli.utils import parse_options
 
+    conf = ctx.obj.get("config", {})
+    if "storage" not in conf:
+        raise ValueError("Missing storage configuration key")
+
     (_, kw) = parse_options(options)
     logger.debug(f"kw: {kw}")
     visit_date = kw.get("visit_date")
@@ -78,7 +101,7 @@
         visit_date = iso8601.parse_date(visit_date)
         kw["visit_date"] = visit_date
 
-    loader = get_loader(type, url=url, **kw)
+    loader = get_loader(type, url=url, storage=conf["storage"], **kw)
     result = loader.load()
     click.echo(result)
 
diff --git a/swh/loader/core/loader.py b/swh/loader/core/loader.py
--- a/swh/loader/core/loader.py
+++ b/swh/loader/core/loader.py
@@ -3,7 +3,6 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
-from abc import ABCMeta, abstractmethod
 import datetime
 import hashlib
 import logging
@@ -26,24 +25,82 @@
     Snapshot,
 )
 from swh.storage import get_storage
+from swh.storage.interface import StorageInterface
 from swh.storage.utils import now
 
 DEFAULT_CONFIG: Dict[str, Any] = {
     "max_content_size": 100 * 1024 * 1024,
-    "save_data": False,
-    "save_data_path": "",
-    "storage": {"cls": "memory"},
 }
 
 
-class BaseLoader(metaclass=ABCMeta):
-    """Mixin base class for loader.
+class Loader:
+    """The base class for a Software Heritage Loader.
 
-    To use this class, you must:
+    A loader retrieves origin information (git/mercurial/svn repositories, pypi/npm/...
+    package artifacts), ingests the contents/directories/revisions/releases/snapshot to
+    the storage backend.
+
+    For now, this just exposes 2 static methods (from_config, from_configfile) to
+    centralize and ease the loader instantiation.
+
+    Args:
+      storage: the instance of the Storage being used to register the
+        origin information
+
+    """
+
+    def __init__(
+        self, storage: StorageInterface, max_content_size: Optional[int] = None,
+    ):
+        self.storage = storage
+        self.max_content_size = int(max_content_size) if max_content_size else None
+
+    @classmethod
+    def from_config(cls, storage: Dict[str, Any], **config: Any):
+        """Instantiate a loader from a configuration dict.
+
+        This is basically a backwards-compatibility shim for the CLI.
+
+        Args:
+          storage: instantiation config for the storage
+          config: the configuration dict for the loader, with the following keys:
+            - credentials (optional): credentials list for the scheduler
+            - any other kwargs passed to the loader.
+
+        Returns:
+          the instantiated loader
+        """
+        # Drop the legacy config keys which aren't used for this generation of loader.
+        for legacy_key in ("storage", "celery"):
+            config.pop(legacy_key, None)
+
+        # Instantiate the storage
+        storage_instance = get_storage(**storage)
+        return cls(storage=storage_instance, **config)
+
+    @classmethod
+    def from_configfile(cls, **kwargs: Any):
+        """Instantiate a loader from the configuration loaded from the
+        SWH_CONFIG_FILENAME envvar, with potential extra keyword arguments if their
+        value is not None.
+
+        Args:
+            kwargs: kwargs passed to the loader instantiation
+
+        """
+        config = dict(load_from_envvar(DEFAULT_CONFIG))
+        config.update({k: v for k, v in kwargs.items() if v is not None})
+        return cls.from_config(**config)
+
+
+class BaseLoader(Loader):
+    """Mixin base class for (D)VCS loaders (e.g svn, git, mercurial, ...).
+
+    To define such loaders, you must:
 
     - inherit from this class
 
-    - and implement the @abstractmethod methods:
+    - and implement following methods:
 
       - :func:`prepare`: First step executed by the loader to prepare some
         state needed by the `func`:load method.
@@ -73,15 +130,12 @@
 
     def __init__(
         self,
+        storage: StorageInterface,
         logging_class: Optional[str] = None,
-        config: Optional[Dict[str, Any]] = None,
+        save_data_path: Optional[str] = None,
+        max_content_size: Optional[int] = None,
     ):
-        if config:
-            self.config = config
-        else:
-            self.config = load_from_envvar(DEFAULT_CONFIG)
-
-        self.storage = get_storage(**self.config["storage"])
+        super().__init__(storage=storage, max_content_size=max_content_size)
 
         if logging_class is None:
             logging_class = "%s.%s" % (
@@ -93,28 +147,24 @@
         _log = logging.getLogger("requests.packages.urllib3.connectionpool")
         _log.setLevel(logging.WARN)
 
-        self.max_content_size = self.config["max_content_size"]
-
         # possibly overridden in self.prepare method
         self.visit_date: Optional[datetime.datetime] = None
-
         self.origin: Optional[Origin] = None
 
         if not hasattr(self, "visit_type"):
             self.visit_type: Optional[str] = None
 
         self.origin_metadata: Dict[str, Any] = {}
-
         self.loaded_snapshot_id: Optional[Sha1Git] = None
 
-        # Make sure the config is sane
-        save_data = self.config.get("save_data")
-        if save_data:
-            path = self.config["save_data_path"]
+        if save_data_path:
+            path = save_data_path
             os.stat(path)
             if not os.access(path, os.R_OK | os.W_OK):
                 raise PermissionError("Permission denied: %r" % path)
 
+        self.save_data_path = save_data_path
+
     def save_data(self) -> None:
         """Save the data associated to the current load"""
         raise NotImplementedError
@@ -129,7 +179,7 @@
             origin_url_hash = hashlib.sha1(url).hexdigest()
 
             path = "%s/sha1:%s/%s/%s" % (
-                self.config["save_data_path"],
+                self.save_data_path,
                 origin_url_hash[0:2],
                 origin_url_hash,
                 year,
@@ -146,21 +196,19 @@
         """
         self.storage.flush()
 
-    @abstractmethod
     def cleanup(self) -> None:
         """Last step executed by the loader.
 
         """
-        pass
+        raise NotImplementedError
 
-    @abstractmethod
     def prepare_origin_visit(self, *args, **kwargs) -> None:
         """First step executed by the loader to prepare origin and visit
            references. Set/update self.origin, and
            optionally self.origin_url, self.visit_date.
 
         """
-        pass
+        raise NotImplementedError
 
     def _store_origin_visit(self) -> None:
         """Store origin and visit references. Sets the self.visit references.
@@ -185,7 +233,6 @@
             )
         )[0]
 
-    @abstractmethod
     def prepare(self, *args, **kwargs) -> None:
         """Second step executed by the loader to prepare some state needed by
            the loader.
@@ -194,7 +241,7 @@
            NotFound exception if the origin to ingest is not found.
 
         """
-        pass
+        raise NotImplementedError
 
     def get_origin(self) -> Origin:
         """Get the origin that is currently being loaded.
@@ -207,7 +254,6 @@
         assert self.origin
         return self.origin
 
-    @abstractmethod
     def fetch_data(self) -> bool:
         """Fetch the data from the source the loader is currently loading
            (ex: git/hg/svn/... repository).
@@ -217,16 +263,15 @@
             to be called again to complete loading.
 
         """
-        pass
+        raise NotImplementedError
 
-    @abstractmethod
     def store_data(self):
         """Store fetched data in the database.
 
         Should call the :func:`maybe_load_xyz` methods, which handle the
         bundles sent to storage, rather than send directly.
         """
-        pass
+        raise NotImplementedError
 
     def store_metadata(self) -> None:
         """Store fetched metadata in the database.
@@ -423,7 +468,7 @@
 
     def store_data(self) -> None:
         assert self.origin
-        if self.config.get("save_data"):
+        if self.save_data_path:
             self.save_data()
 
         if self.has_contents():
diff --git a/swh/loader/core/tests/test_loader.py b/swh/loader/core/tests/test_loader.py
--- a/swh/loader/core/tests/test_loader.py
+++ b/swh/loader/core/tests/test_loader.py
@@ -7,7 +7,7 @@
 import hashlib
 import logging
 
-from swh.loader.core.loader import DEFAULT_CONFIG, BaseLoader, DVCSLoader
+from swh.loader.core.loader import BaseLoader, DVCSLoader
 from swh.loader.exception import NotFound
 from swh.loader.tests import assert_last_visit_matches
 from swh.model.hashutil import hash_to_bytes
@@ -77,54 +77,51 @@
         pass
 
 
-def test_base_loader(swh_config):
-    loader = DummyBaseLoader()
+def test_base_loader(swh_storage):
+    loader = DummyBaseLoader(swh_storage)
     result = loader.load()
     assert result == {"status": "eventful"}
 
 
-def test_base_loader_with_config(swh_config):
-    loader = DummyBaseLoader("logger-name", DEFAULT_CONFIG)
+def test_base_loader_with_config(swh_storage):
+    loader = DummyBaseLoader(swh_storage, "logger-name")
     result = loader.load()
     assert result == {"status": "eventful"}
 
 
-def test_dvcs_loader(swh_config):
-    loader = DummyDVCSLoader()
+def test_dvcs_loader(swh_storage):
+    loader = DummyDVCSLoader(swh_storage)
     result = loader.load()
     assert result == {"status": "eventful"}
 
 
-def test_dvcs_loader_with_config(swh_config):
-    loader = DummyDVCSLoader("another-logger", DEFAULT_CONFIG)
+def test_dvcs_loader_with_config(swh_storage):
+    loader = DummyDVCSLoader(swh_storage, "another-logger")
     result = loader.load()
     assert result == {"status": "eventful"}
 
 
-def test_loader_logger_default_name(swh_config):
-    loader = DummyBaseLoader()
+def test_loader_logger_default_name(swh_storage):
+    loader = DummyBaseLoader(swh_storage)
     assert isinstance(loader.log, logging.Logger)
     assert loader.log.name == "swh.loader.core.tests.test_loader.DummyBaseLoader"
 
-    loader = DummyDVCSLoader()
+    loader = DummyDVCSLoader(swh_storage)
     assert isinstance(loader.log, logging.Logger)
     assert loader.log.name == "swh.loader.core.tests.test_loader.DummyDVCSLoader"
 
 
-def test_loader_logger_with_name(swh_config):
-    loader = DummyBaseLoader("some.logger.name")
+def test_loader_logger_with_name(swh_storage):
+    loader = DummyBaseLoader(swh_storage, "some.logger.name")
     assert isinstance(loader.log, logging.Logger)
     assert loader.log.name == "some.logger.name"
 
 
-def test_loader_save_data_path(swh_config, tmp_path):
-    loader = DummyBaseLoader("some.logger.name.1")
+def test_loader_save_data_path(swh_storage, tmp_path):
+    loader = DummyBaseLoader(swh_storage, "some.logger.name.1", save_data_path=tmp_path)
     url = "http://bitbucket.org/something"
     loader.origin = Origin(url=url)
     loader.visit_date = datetime.datetime(year=2019, month=10, day=1)
-    loader.config = {
-        "save_data_path": tmp_path,
-    }
 
     hash_url = hashlib.sha1(url.encode("utf-8")).hexdigest()
     expected_save_path = "%s/sha1:%s/%s/2019" % (str(tmp_path), hash_url[0:2], hash_url)
@@ -164,11 +161,11 @@
         raise RuntimeError("Failed to get contents!")
 
 
-def test_dvcs_loader_exc_partial_visit(swh_config, caplog):
+def test_dvcs_loader_exc_partial_visit(swh_storage, caplog):
     logger_name = "dvcsloaderexc"
     caplog.set_level(logging.ERROR, logger=logger_name)
 
-    loader = DummyDVCSLoaderExc(logging_class=logger_name)
+    loader = DummyDVCSLoaderExc(swh_storage, logging_class=logger_name)
     # fake the loading ending up in a snapshot
     loader.loaded_snapshot_id = hash_to_bytes(
         "9e4dd2b40d1b46b70917c0949aa2195c823a648e"
@@ -203,11 +200,11 @@
         self.storage = BrokenStorageProxy(self.storage)
 
 
-def test_dvcs_loader_storage_exc_failed_visit(swh_config, caplog):
+def test_dvcs_loader_storage_exc_failed_visit(swh_storage, caplog):
     logger_name = "dvcsloaderexc"
     caplog.set_level(logging.ERROR, logger=logger_name)
 
-    loader = DummyDVCSLoaderStorageExc(logging_class=logger_name)
+    loader = DummyDVCSLoaderStorageExc(swh_storage, logging_class=logger_name)
     result = loader.load()
 
     assert result == {"status": "failed"}
@@ -231,8 +228,8 @@
         }
 
 
-def test_loader_not_found(swh_config, caplog):
-    loader = DummyDVCSLoaderNotFound()
+def test_loader_not_found(swh_storage, caplog):
+    loader = DummyDVCSLoaderNotFound(swh_storage)
     result = loader.load()
 
     assert result == {"status": "uneventful"}
diff --git a/swh/loader/package/archive/loader.py b/swh/loader/package/archive/loader.py
--- a/swh/loader/package/archive/loader.py
+++ b/swh/loader/package/archive/loader.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2019  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -20,6 +20,7 @@
     Sha1Git,
     TimestampWithTimezone,
 )
+from swh.storage.interface import StorageInterface
 
 logger = logging.getLogger(__name__)
 SWH_PERSON = Person(
@@ -71,9 +72,11 @@
 
     def __init__(
         self,
+        storage: StorageInterface,
         url: str,
         artifacts: Sequence[Dict[str, Any]],
         identity_artifact_keys: Optional[Sequence[str]] = None,
+        max_content_size: Optional[int] = None,
     ):
         """Loader constructor.
 
@@ -98,7 +101,7 @@
                 "identity" of an artifact
 
         """
-        super().__init__(url=url)
+        super().__init__(storage=storage, url=url, max_content_size=max_content_size)
         self.artifacts = artifacts  # assume order is enforced in the lister
         self.identity_artifact_keys = identity_artifact_keys
 
diff --git a/swh/loader/package/archive/tasks.py b/swh/loader/package/archive/tasks.py
--- a/swh/loader/package/archive/tasks.py
+++ b/swh/loader/package/archive/tasks.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2019  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -11,4 +11,5 @@
 @shared_task(name=__name__ + ".LoadArchive")
 def load_archive_files(*, url=None, artifacts=None):
     """Load archive's artifacts (e.g gnu, etc...)"""
-    return ArchiveLoader(url, artifacts).load()
+    loader = ArchiveLoader.from_configfile(url=url, artifacts=artifacts)
+    return loader.load()
diff --git a/swh/loader/package/archive/tests/test_archive.py b/swh/loader/package/archive/tests/test_archive.py
--- a/swh/loader/package/archive/tests/test_archive.py
+++ b/swh/loader/package/archive/tests/test_archive.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2019-2020 The Software Heritage developers
+# Copyright (C) 2019-2021 The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -70,10 +70,11 @@
 }
 
 
-def visit_with_no_artifact_found(swh_config, requests_mock_datadir):
+def test_archive_visit_with_no_artifact_found(swh_storage, requests_mock_datadir):
     url = URL
     unknown_artifact_url = "https://ftp.g.o/unknown/8sync-0.1.0.tar.gz"
     loader = ArchiveLoader(
+        swh_storage,
         url,
         artifacts=[
             {
@@ -89,7 +90,7 @@
     actual_load_status = loader.load()
     assert actual_load_status["status"] == "uneventful"
     assert actual_load_status["snapshot_id"] is not None
-    stats = get_stats(loader.storage)
+    stats = get_stats(swh_storage)
 
     assert {
         "content": 0,
@@ -102,20 +103,20 @@
         "snapshot": 1,
     } == stats
 
-    assert_last_visit_matches(loader.storage, url, status="partial", type="tar")
+    assert_last_visit_matches(swh_storage, url, status="partial", type="tar")
 
 
-def test_check_revision_metadata_structure(swh_config, requests_mock_datadir):
-    loader = ArchiveLoader(url=URL, artifacts=GNU_ARTIFACTS)
+def test_archive_check_revision_metadata_structure(swh_storage, requests_mock_datadir):
+    loader = ArchiveLoader(swh_storage, URL, artifacts=GNU_ARTIFACTS)
 
     actual_load_status = loader.load()
     assert actual_load_status["status"] == "eventful"
     assert actual_load_status["snapshot_id"] is not None
 
-    assert_last_visit_matches(loader.storage, URL, status="full", type="tar")
+    assert_last_visit_matches(swh_storage, URL, status="full", type="tar")
 
     expected_revision_id = hash_to_bytes("44183488c0774ce3c957fa19ba695cf18a4a42b3")
-    revision = loader.storage.revision_get([expected_revision_id])[0]
+    revision = swh_storage.revision_get([expected_revision_id])[0]
     assert revision is not None
 
     check_metadata_paths(
@@ -136,11 +137,13 @@
         )
 
 
-def test_visit_with_release_artifact_no_prior_visit(swh_config, requests_mock_datadir):
+def test_archive_visit_with_release_artifact_no_prior_visit(
+    swh_storage, requests_mock_datadir
+):
     """With no prior visit, load a gnu project ends up with 1 snapshot
 
     """
-    loader = ArchiveLoader(url=URL, artifacts=GNU_ARTIFACTS)
+    loader = ArchiveLoader(swh_storage, URL, artifacts=GNU_ARTIFACTS)
 
     actual_load_status = loader.load()
     assert actual_load_status["status"] == "eventful"
@@ -154,9 +157,9 @@
         == expected_snapshot_first_visit_id
     )
 
-    assert_last_visit_matches(loader.storage, URL, status="full", type="tar")
+    assert_last_visit_matches(swh_storage, URL, status="full", type="tar")
 
-    stats = get_stats(loader.storage)
+    stats = get_stats(swh_storage)
     assert {
         "content": len(_expected_new_contents_first_visit),
         "directory": len(_expected_new_directories_first_visit),
@@ -169,13 +172,13 @@
     } == stats
 
     expected_contents = map(hash_to_bytes, _expected_new_contents_first_visit)
-    assert list(loader.storage.content_missing_per_sha1(expected_contents)) == []
+    assert list(swh_storage.content_missing_per_sha1(expected_contents)) == []
 
     expected_dirs = map(hash_to_bytes, _expected_new_directories_first_visit)
-    assert list(loader.storage.directory_missing(expected_dirs)) == []
+    assert list(swh_storage.directory_missing(expected_dirs)) == []
 
     expected_revs = map(hash_to_bytes, _expected_new_revisions_first_visit)
-    assert list(loader.storage.revision_missing(expected_revs)) == []
+    assert list(swh_storage.revision_missing(expected_revs)) == []
 
     expected_snapshot = Snapshot(
         id=expected_snapshot_first_visit_id,
@@ -190,28 +193,28 @@
         },
     )
 
-    check_snapshot(expected_snapshot, loader.storage)
+    check_snapshot(expected_snapshot, swh_storage)
 
 
-def test_2_visits_without_change(swh_config, requests_mock_datadir):
+def test_archive_2_visits_without_change(swh_storage, requests_mock_datadir):
     """With no prior visit, load a gnu project ends up with 1 snapshot
 
     """
     url = URL
-    loader = ArchiveLoader(url, artifacts=GNU_ARTIFACTS)
+    loader = ArchiveLoader(swh_storage, url, artifacts=GNU_ARTIFACTS)
 
     actual_load_status = loader.load()
     assert actual_load_status["status"] == "eventful"
     assert actual_load_status["snapshot_id"] is not None
 
-    assert_last_visit_matches(loader.storage, url, status="full", type="tar")
+    assert_last_visit_matches(swh_storage, url, status="full", type="tar")
 
     actual_load_status2 = loader.load()
     assert actual_load_status2["status"] == "uneventful"
     assert actual_load_status2["snapshot_id"] is not None
     assert actual_load_status["snapshot_id"] == actual_load_status2["snapshot_id"]
 
-    assert_last_visit_matches(loader.storage, url, status="full", type="tar")
+    assert_last_visit_matches(swh_storage, url, status="full", type="tar")
 
     urls = [
         m.url
@@ -221,21 +224,21 @@
     assert len(urls) == 1
 
 
-def test_2_visits_with_new_artifact(swh_config, requests_mock_datadir):
+def test_archive_2_visits_with_new_artifact(swh_storage, requests_mock_datadir):
     """With no prior visit, load a gnu project ends up with 1 snapshot
 
     """
     url = URL
     artifact1 = GNU_ARTIFACTS[0]
-    loader = ArchiveLoader(url, [artifact1])
+    loader = ArchiveLoader(swh_storage, url, [artifact1])
 
     actual_load_status = loader.load()
     assert actual_load_status["status"] == "eventful"
     assert actual_load_status["snapshot_id"] is not None
 
-    assert_last_visit_matches(loader.storage, url, status="full", type="tar")
+    assert_last_visit_matches(swh_storage, url, status="full", type="tar")
 
-    stats = get_stats(loader.storage)
+    stats = get_stats(swh_storage)
     assert {
         "content": len(_expected_new_contents_first_visit),
         "directory": len(_expected_new_directories_first_visit),
@@ -262,17 +265,15 @@
         "version": "0.2.0",
     }
 
-    loader2 = ArchiveLoader(url, [artifact1, artifact2])
-    # implementation detail: share the storage in between visits
-    loader2.storage = loader.storage
-    stats2 = get_stats(loader2.storage)
+    loader2 = ArchiveLoader(swh_storage, url, [artifact1, artifact2])
+    stats2 = get_stats(swh_storage)
     assert stats == stats2  # ensure we share the storage
 
     actual_load_status2 = loader2.load()
     assert actual_load_status2["status"] == "eventful"
     assert actual_load_status2["snapshot_id"] is not None
 
-    stats2 = get_stats(loader.storage)
+    stats2 = get_stats(swh_storage)
     assert {
         "content": len(_expected_new_contents_first_visit) + 14,
         "directory": len(_expected_new_directories_first_visit) + 8,
@@ -284,7 +285,7 @@
         "snapshot": 1 + 1,
     } == stats2
 
-    assert_last_visit_matches(loader.storage, url, status="full", type="tar")
+    assert_last_visit_matches(swh_storage, url, status="full", type="tar")
 
     urls = [
         m.url
@@ -295,7 +296,7 @@
     assert len(urls) == 2
 
 
-def test_2_visits_without_change_not_gnu(swh_config, requests_mock_datadir):
+def test_archive_2_visits_without_change_not_gnu(swh_storage, requests_mock_datadir):
     """Load a project archive (not gnu) ends up with 1 snapshot
 
     """
@@ -315,18 +316,21 @@
     # Here the loader defines the id_keys to use for existence in the snapshot
     # It's not the default archive loader which
     loader = ArchiveLoader(
-        url, artifacts=artifacts, identity_artifact_keys=["sha256", "length", "url"]
+        swh_storage,
+        url,
+        artifacts=artifacts,
+        identity_artifact_keys=["sha256", "length", "url"],
     )
 
     actual_load_status = loader.load()
     assert actual_load_status["status"] == "eventful"
     assert actual_load_status["snapshot_id"] is not None
-    assert_last_visit_matches(loader.storage, url, status="full", type="tar")
+    assert_last_visit_matches(swh_storage, url, status="full", type="tar")
 
     actual_load_status2 = loader.load()
     assert actual_load_status2["status"] == "uneventful"
     assert actual_load_status2["snapshot_id"] == actual_load_status["snapshot_id"]
-    assert_last_visit_matches(loader.storage, url, status="full", type="tar")
+    assert_last_visit_matches(swh_storage, url, status="full", type="tar")
 
     urls = [
         m.url
@@ -336,7 +340,7 @@
     assert len(urls) == 1
 
 
-def test_artifact_identity():
+def test_archive_artifact_identity():
     """Compute primary key should return the right identity
 
     """
diff --git a/swh/loader/package/archive/tests/test_tasks.py b/swh/loader/package/archive/tests/test_tasks.py
--- a/swh/loader/package/archive/tests/test_tasks.py
+++ b/swh/loader/package/archive/tests/test_tasks.py
@@ -1,21 +1,21 @@
-# Copyright (C) 2019  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 
-def test_archive_loader(
+def test_tasks_archive_loader(
     mocker, swh_scheduler_celery_app, swh_scheduler_celery_worker, swh_config
 ):
-    mock_loader = mocker.patch("swh.loader.package.archive.loader.ArchiveLoader.load")
-    mock_loader.return_value = {"status": "eventful"}
+    mock_load = mocker.patch("swh.loader.package.archive.loader.ArchiveLoader.load")
+    mock_load.return_value = {"status": "eventful"}
 
     res = swh_scheduler_celery_app.send_task(
         "swh.loader.package.archive.tasks.LoadArchive",
-        kwargs={"url": "some-url", "artifacts": []},
+        kwargs=dict(url="https://gnu.org/", artifacts=[]),
     )
     assert res
     res.wait()
     assert res.successful()
-
+    assert mock_load.called
     assert res.result == {"status": "eventful"}
diff --git a/swh/loader/package/cran/loader.py b/swh/loader/package/cran/loader.py
--- a/swh/loader/package/cran/loader.py
+++ b/swh/loader/package/cran/loader.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2019-2020  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -24,6 +24,7 @@
     Sha1Git,
     TimestampWithTimezone,
 )
+from swh.storage.interface import StorageInterface
 
 logger = logging.getLogger(__name__)
 
@@ -52,7 +53,13 @@
 class CRANLoader(PackageLoader[CRANPackageInfo]):
     visit_type = "cran"
 
-    def __init__(self, url: str, artifacts: List[Dict]):
+    def __init__(
+        self,
+        storage: StorageInterface,
+        url: str,
+        artifacts: List[Dict],
+        max_content_size: Optional[int] = None,
+    ):
         """Loader constructor.
 
         Args:
@@ -60,7 +67,7 @@
             artifacts: List of associated artifact for the origin url
 
         """
-        super().__init__(url=url)
+        super().__init__(storage=storage, url=url, max_content_size=max_content_size)
         # explicit what we consider the artifact identity
         self.artifacts = artifacts
 
diff --git a/swh/loader/package/cran/tasks.py b/swh/loader/package/cran/tasks.py
--- a/swh/loader/package/cran/tasks.py
+++ b/swh/loader/package/cran/tasks.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2019-2020  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -11,4 +11,4 @@
 @shared_task(name=__name__ + ".LoadCRAN")
 def load_cran(url=None, artifacts=[]):
     """Load CRAN's artifacts"""
-    return CRANLoader(url, artifacts).load()
+    return CRANLoader.from_configfile(url=url, artifacts=artifacts).load()
diff --git a/swh/loader/package/cran/tests/test_cran.py b/swh/loader/package/cran/tests/test_cran.py
--- a/swh/loader/package/cran/tests/test_cran.py
+++ b/swh/loader/package/cran/tests/test_cran.py
@@ -121,7 +121,7 @@
 
 
 @pytest.mark.fs
-def test_extract_intrinsic_metadata(tmp_path, datadir):
+def test_cran_extract_intrinsic_metadata(tmp_path, datadir):
     """Parsing existing archive's PKG-INFO should yield results"""
     uncompressed_archive_path = str(tmp_path)
     # sample url
@@ -152,7 +152,7 @@
 
 
 @pytest.mark.fs
-def test_extract_intrinsic_metadata_failures(tmp_path):
+def test_cran_extract_intrinsic_metadata_failures(tmp_path):
     """Parsing inexistent path/archive/PKG-INFO yield None"""
     # inexistent first level path
     assert extract_intrinsic_metadata("/something-inexistent") == {}
@@ -164,7 +164,7 @@
     assert extract_intrinsic_metadata(tmp_path) == {}
 
 
-def test_cran_one_visit(swh_config, requests_mock_datadir):
+def test_cran_one_visit(swh_storage, requests_mock_datadir):
     version = "2.22-6"
     base_url = "https://cran.r-project.org"
     origin_url = f"{base_url}/Packages/Recommended_KernSmooth/index.html"
@@ -172,7 +172,7 @@
         f"{base_url}/src_contrib_1.4.0_Recommended_KernSmooth_{version}.tar.gz"  # noqa
     )
     loader = CRANLoader(
-        origin_url, artifacts=[{"url": artifact_url, "version": version,}]
+        swh_storage, origin_url, artifacts=[{"url": artifact_url, "version": version,}]
     )
 
     actual_load_status = loader.load()
@@ -182,11 +182,11 @@
         "snapshot_id": SNAPSHOT.id.hex(),
     }
 
-    check_snapshot(SNAPSHOT, loader.storage)
+    check_snapshot(SNAPSHOT, swh_storage)
 
-    assert_last_visit_matches(loader.storage, origin_url, status="full", type="cran")
+    assert_last_visit_matches(swh_storage, origin_url, status="full", type="cran")
 
-    visit_stats = get_stats(loader.storage)
+    visit_stats = get_stats(swh_storage)
     assert {
         "content": 33,
         "directory": 7,
@@ -207,7 +207,7 @@
     assert len(urls) == 1
 
 
-def test_cran_2_visits_same_origin(swh_config, requests_mock_datadir):
+def test_cran_2_visits_same_origin(swh_storage, requests_mock_datadir):
     """Multiple visits on the same origin, only 1 archive fetch"""
     version = "2.22-6"
     base_url = "https://cran.r-project.org"
@@ -216,7 +216,7 @@
         f"{base_url}/src_contrib_1.4.0_Recommended_KernSmooth_{version}.tar.gz"  # noqa
     )
     loader = CRANLoader(
-        origin_url, artifacts=[{"url": artifact_url, "version": version}]
+        swh_storage, origin_url, artifacts=[{"url": artifact_url, "version": version}]
     )
 
     # first visit
@@ -228,11 +228,11 @@
         "snapshot_id": SNAPSHOT.id.hex(),
     }
 
-    check_snapshot(SNAPSHOT, loader.storage)
+    check_snapshot(SNAPSHOT, swh_storage)
 
-    assert_last_visit_matches(loader.storage, origin_url, status="full", type="cran")
+    assert_last_visit_matches(swh_storage, origin_url, status="full", type="cran")
 
-    visit_stats = get_stats(loader.storage)
+    visit_stats = get_stats(swh_storage)
     assert {
         "content": 33,
         "directory": 7,
@@ -252,9 +252,9 @@
         "snapshot_id": expected_snapshot_id,
     }
 
-    assert_last_visit_matches(loader.storage, origin_url, status="full", type="cran")
+    assert_last_visit_matches(swh_storage, origin_url, status="full", type="cran")
 
-    visit_stats2 = get_stats(loader.storage)
+    visit_stats2 = get_stats(swh_storage)
     visit_stats["origin_visit"] += 1
     assert visit_stats2 == visit_stats, "same stats as 1st visit, +1 visit"
 
@@ -266,7 +266,7 @@
     assert len(urls) == 1, "visited one time artifact url (across 2 visits)"
 
 
-def test_parse_debian_control(datadir):
+def test_cran_parse_debian_control(datadir):
     description_file = os.path.join(datadir, "description", "acepack")
 
     actual_metadata = parse_debian_control(description_file)
@@ -287,7 +287,7 @@
     }
 
 
-def test_parse_debian_control_unicode_issue(datadir):
+def test_cran_parse_debian_control_unicode_issue(datadir):
     # iso-8859-1 caused failure, now fixed
     description_file = os.path.join(datadir, "description", "KnownBR")
 
@@ -317,7 +317,7 @@
     ["build_extrinsic_snapshot_metadata", "build_extrinsic_origin_metadata",],
 )
 def test_cran_fail_to_build_or_load_extrinsic_metadata(
-    method_name, swh_config, requests_mock_datadir
+    method_name, swh_storage, requests_mock_datadir
 ):
     """problem during loading: {visit: failed, status: failed, no snapshot}
 
@@ -335,7 +335,9 @@
         side_effect=ValueError("Fake to fail to build or load extrinsic metadata"),
     ):
         loader = CRANLoader(
-            origin_url, artifacts=[{"url": artifact_url, "version": version}]
+            swh_storage,
+            origin_url,
+            artifacts=[{"url": artifact_url, "version": version}],
         )
 
         actual_load_status = loader.load()
@@ -345,7 +347,7 @@
             "snapshot_id": SNAPSHOT.id.hex(),
         }
 
-        visit_stats = get_stats(loader.storage)
+        visit_stats = get_stats(swh_storage)
         assert {
             "content": 33,
             "directory": 7,
@@ -358,5 +360,5 @@
         } == visit_stats
 
         assert_last_visit_matches(
-            loader.storage, origin_url, status="partial", type="cran"
+            swh_storage, origin_url, status="partial", type="cran"
         )
diff --git a/swh/loader/package/cran/tests/test_tasks.py b/swh/loader/package/cran/tests/test_tasks.py
--- a/swh/loader/package/cran/tests/test_tasks.py
+++ b/swh/loader/package/cran/tests/test_tasks.py
@@ -1,24 +1,23 @@
-# Copyright (C) 2019-2020  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 
-def test_cran_loader(
+def test_tasks_cran_loader(
     mocker, swh_scheduler_celery_app, swh_scheduler_celery_worker, swh_config
 ):
-    mock_loader = mocker.patch("swh.loader.package.cran.loader.CRANLoader.load")
-    mock_loader.return_value = {"status": "eventful"}
+    mock_load = mocker.patch("swh.loader.package.cran.loader.CRANLoader.load")
+    mock_load.return_value = {"status": "eventful"}
 
     res = swh_scheduler_celery_app.send_task(
         "swh.loader.package.cran.tasks.LoadCRAN",
-        kwargs={
-            "url": "some-url",
-            "artifacts": {"version": "1.2.3", "url": "artifact-url"},
-        },
+        kwargs=dict(
+            url="some-url", artifacts=[{"version": "1.2.3", "url": "artifact-url"}],
+        ),
     )
     assert res
     res.wait()
     assert res.successful()
-
+    assert mock_load.called
     assert res.result == {"status": "eventful"}
diff --git a/swh/loader/package/debian/loader.py b/swh/loader/package/debian/loader.py
--- a/swh/loader/package/debian/loader.py
+++ b/swh/loader/package/debian/loader.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2017-2019  The Software Heritage developers
+# Copyright (C) 2017-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -34,6 +34,7 @@
     Sha1Git,
     TimestampWithTimezone,
 )
+from swh.storage.interface import StorageInterface
 
 logger = logging.getLogger(__name__)
 UPLOADERS_SPLIT = re.compile(r"(?<=\>)\s*,\s*")
@@ -103,7 +104,14 @@
 
     visit_type = "deb"
 
-    def __init__(self, url: str, date: str, packages: Mapping[str, Any]):
+    def __init__(
+        self,
+        storage: StorageInterface,
+        url: str,
+        date: str,
+        packages: Mapping[str, Any],
+        max_content_size: Optional[int] = None,
+    ):
         """Debian Loader implementation.
 
         Args:
@@ -143,7 +151,7 @@
               }
 
         """
-        super().__init__(url=url)
+        super().__init__(storage=storage, url=url, max_content_size=max_content_size)
         self.packages = packages
 
     def get_versions(self) -> Sequence[str]:
diff --git a/swh/loader/package/debian/tasks.py b/swh/loader/package/debian/tasks.py
--- a/swh/loader/package/debian/tasks.py
+++ b/swh/loader/package/debian/tasks.py
@@ -11,4 +11,5 @@
 @shared_task(name=__name__ + ".LoadDebian")
 def load_deb_package(*, url, date, packages):
     """Load Debian package"""
-    return DebianLoader(url, date, packages).load()
+    loader = DebianLoader.from_configfile(url=url, date=date, packages=packages)
+    return loader.load()
diff --git a/swh/loader/package/debian/tests/test_debian.py b/swh/loader/package/debian/tests/test_debian.py
--- a/swh/loader/package/debian/tests/test_debian.py
+++ b/swh/loader/package/debian/tests/test_debian.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2019-2020  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -99,12 +99,15 @@
 }
 
 
-def test_debian_first_visit(swh_config, requests_mock_datadir):
+def test_debian_first_visit(swh_storage, requests_mock_datadir):
     """With no prior visit, load a gnu project ends up with 1 snapshot
 
     """
     loader = DebianLoader(
-        url=URL, date="2019-10-12T05:58:09.165557+00:00", packages=PACKAGE_PER_VERSION,
+        swh_storage,
+        URL,
+        date="2019-10-12T05:58:09.165557+00:00",
+        packages=PACKAGE_PER_VERSION,
     )
 
     actual_load_status = loader.load()
@@ -114,9 +117,9 @@
         "snapshot_id": expected_snapshot_id,
     }
 
-    assert_last_visit_matches(loader.storage, URL, status="full", type="deb")
+    assert_last_visit_matches(swh_storage, URL, status="full", type="deb")
 
-    stats = get_stats(loader.storage)
+    stats = get_stats(swh_storage)
     assert {
         "content": 42,
         "directory": 2,
@@ -138,15 +141,18 @@
         },
     )  # different than the previous loader as no release is done
 
-    check_snapshot(expected_snapshot, loader.storage)
+    check_snapshot(expected_snapshot, swh_storage)
 
 
-def test_debian_first_visit_then_another_visit(swh_config, requests_mock_datadir):
+def test_debian_first_visit_then_another_visit(swh_storage, requests_mock_datadir):
     """With no prior visit, load a debian project ends up with 1 snapshot
 
     """
     loader = DebianLoader(
-        url=URL, date="2019-10-12T05:58:09.165557+00:00", packages=PACKAGE_PER_VERSION
+        swh_storage,
+        URL,
+        date="2019-10-12T05:58:09.165557+00:00",
+        packages=PACKAGE_PER_VERSION,
     )
 
     actual_load_status = loader.load()
@@ -157,9 +163,9 @@
         "snapshot_id": expected_snapshot_id,
     }
 
-    assert_last_visit_matches(loader.storage, URL, status="full", type="deb")
+    assert_last_visit_matches(swh_storage, URL, status="full", type="deb")
 
-    stats = get_stats(loader.storage)
+    stats = get_stats(swh_storage)
     assert {
         "content": 42,
         "directory": 2,
@@ -181,14 +187,14 @@
         },
     )  # different than the previous loader as no release is done
 
-    check_snapshot(expected_snapshot, loader.storage)
+    check_snapshot(expected_snapshot, swh_storage)
 
     # No change in between load
     actual_load_status2 = loader.load()
     assert actual_load_status2["status"] == "uneventful"
-    assert_last_visit_matches(loader.storage, URL, status="full", type="deb")
+    assert_last_visit_matches(swh_storage, URL, status="full", type="deb")
 
-    stats2 = get_stats(loader.storage)
+    stats2 = get_stats(swh_storage)
     assert {
         "content": 42 + 0,
         "directory": 2 + 0,
@@ -209,7 +215,7 @@
     assert len(urls) == len(set(urls))
 
 
-def test_uid_to_person():
+def test_debian_uid_to_person():
     uid = "Someone Name <someone@orga.org>"
     actual_person = uid_to_person(uid)
 
@@ -220,7 +226,7 @@
     }
 
 
-def test_prepare_person():
+def test_debian_prepare_person():
     actual_author = prepare_person(
         {
             "name": "Someone Name",
@@ -236,7 +242,7 @@
     )
 
 
-def test_download_package(datadir, tmpdir, requests_mock_datadir):
+def test_debian_download_package(datadir, tmpdir, requests_mock_datadir):
     tmpdir = str(tmpdir)  # py3.5 work around (LocalPath issue)
     p_info = DebianPackageInfo.from_metadata(PACKAGE_FILES, url=URL)
     all_hashes = download_package(p_info, tmpdir)
@@ -279,7 +285,7 @@
     }
 
 
-def test_dsc_information_ok():
+def test_debian_dsc_information_ok():
     fname = "cicero_0.7.2-3.dsc"
     p_info = DebianPackageInfo.from_metadata(PACKAGE_FILES, url=URL)
     dsc_url, dsc_name = dsc_information(p_info)
@@ -288,7 +294,7 @@
     assert dsc_name == PACKAGE_FILES["files"][fname]["name"]
 
 
-def test_dsc_information_not_found():
+def test_debian_dsc_information_not_found():
     fname = "cicero_0.7.2-3.dsc"
     p_info = DebianPackageInfo.from_metadata(PACKAGE_FILES, url=URL)
     p_info.files.pop(fname)
@@ -299,7 +305,7 @@
     assert dsc_name is None
 
 
-def test_dsc_information_too_many_dsc_entries():
+def test_debian_dsc_information_too_many_dsc_entries():
     # craft an extra dsc file
     fname = "cicero_0.7.2-3.dsc"
     p_info = DebianPackageInfo.from_metadata(PACKAGE_FILES, url=URL)
@@ -315,7 +321,9 @@
         dsc_information(p_info)
 
 
-def test_get_intrinsic_package_metadata(requests_mock_datadir, datadir, tmp_path):
+def test_debian_get_intrinsic_package_metadata(
+    requests_mock_datadir, datadir, tmp_path
+):
     tmp_path = str(tmp_path)  # py3.5 compat.
     p_info = DebianPackageInfo.from_metadata(PACKAGE_FILES, url=URL)
 
@@ -372,9 +380,12 @@
     )
 
 
-def test_debian_multiple_packages(swh_config, requests_mock_datadir):
+def test_debian_multiple_packages(swh_storage, requests_mock_datadir):
     loader = DebianLoader(
-        url=URL, date="2019-10-12T05:58:09.165557+00:00", packages=PACKAGES_PER_VERSION
+        swh_storage,
+        URL,
+        date="2019-10-12T05:58:09.165557+00:00",
+        packages=PACKAGES_PER_VERSION,
     )
 
     actual_load_status = loader.load()
@@ -384,7 +395,7 @@
         "snapshot_id": expected_snapshot_id,
     }
 
-    assert_last_visit_matches(loader.storage, URL, status="full", type="deb")
+    assert_last_visit_matches(swh_storage, URL, status="full", type="deb")
 
     expected_snapshot = Snapshot(
         id=hash_to_bytes(expected_snapshot_id),
@@ -400,10 +411,10 @@
         },
     )
 
-    check_snapshot(expected_snapshot, loader.storage)
+    check_snapshot(expected_snapshot, swh_storage)
 
 
-def test_resolve_revision_from_edge_cases():
+def test_debian_resolve_revision_from_edge_cases():
     """Solving revision with empty data will result in unknown revision
 
     """
@@ -435,7 +446,7 @@
     )
 
 
-def test_resolve_revision_from_edge_cases_hit_and_miss():
+def test_debian_resolve_revision_from_edge_cases_hit_and_miss():
     """Solving revision with inconsistent data will result in unknown revision
 
     """
@@ -456,7 +467,7 @@
     assert actual_revision is None
 
 
-def test_resolve_revision_from():
+def test_debian_resolve_revision_from():
     """Solving revision with consistent data will solve the revision
 
     """
diff --git a/swh/loader/package/debian/tests/test_tasks.py b/swh/loader/package/debian/tests/test_tasks.py
--- a/swh/loader/package/debian/tests/test_tasks.py
+++ b/swh/loader/package/debian/tests/test_tasks.py
@@ -1,21 +1,21 @@
-# Copyright (C) 2019  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 
-def test_debian_loader(
+def test_tasks_debian_loader(
     mocker, swh_scheduler_celery_app, swh_scheduler_celery_worker, swh_config
 ):
-    mock_loader = mocker.patch("swh.loader.package.debian.loader.DebianLoader.load")
-    mock_loader.return_value = {"status": "eventful"}
+    mock_load = mocker.patch("swh.loader.package.debian.loader.DebianLoader.load")
+    mock_load.return_value = {"status": "eventful"}
 
     res = swh_scheduler_celery_app.send_task(
         "swh.loader.package.debian.tasks.LoadDebian",
-        kwargs={"url": "some-url", "date": "some-date", "packages": {}},
+        kwargs=dict(url="some-url", date="some-date", packages={}),
     )
     assert res
     res.wait()
     assert res.successful()
-
+    assert mock_load.called
     assert res.result == {"status": "eventful"}
diff --git a/swh/loader/package/deposit/loader.py b/swh/loader/package/deposit/loader.py
--- a/swh/loader/package/deposit/loader.py
+++ b/swh/loader/package/deposit/loader.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2019-2020  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -12,6 +12,8 @@
 import attr
 import requests
 
+from swh.core.config import load_from_envvar
+from swh.loader.core.loader import DEFAULT_CONFIG
 from swh.loader.package.loader import (
     BasePackageInfo,
     PackageLoader,
@@ -30,6 +32,7 @@
     TimestampWithTimezone,
 )
 from swh.storage.algos.snapshot import snapshot_get_all_branches
+from swh.storage.interface import StorageInterface
 
 logger = logging.getLogger(__name__)
 
@@ -107,19 +110,41 @@
 
     visit_type = "deposit"
 
-    def __init__(self, url: str, deposit_id: str):
+    def __init__(
+        self,
+        storage: StorageInterface,
+        url: str,
+        deposit_id: str,
+        deposit_client: "ApiClient",
+        max_content_size: Optional[int] = None,
+    ):
         """Constructor
 
         Args:
             url: Origin url to associate the artifacts/metadata to
             deposit_id: Deposit identity
+            deposit_client: Deposit api client
 
         """
-        super().__init__(url=url)
+        super().__init__(storage=storage, url=url, max_content_size=max_content_size)
 
-        config_deposit = self.config["deposit"]
         self.deposit_id = deposit_id
-        self.client = ApiClient(url=config_deposit["url"], auth=config_deposit["auth"])
+        self.client = deposit_client
+
+    @classmethod
+    def from_configfile(cls, **kwargs: Any):
+        """Instantiate a loader from the configuration loaded from the
+        SWH_CONFIG_FILENAME envvar, with potential extra keyword arguments if their
+        value is not None.
+
+        Args:
+            kwargs: kwargs passed to the loader instantiation
+
+        """
+        config = dict(load_from_envvar(DEFAULT_CONFIG))
+        config.update({k: v for k, v in kwargs.items() if v is not None})
+        deposit_client = ApiClient(**config.pop("deposit"))
+        return cls.from_config(deposit_client=deposit_client, **config)
 
     def get_versions(self) -> Sequence[str]:
         # only 1 branch 'HEAD' with no alias since we only have 1 snapshot
diff --git a/swh/loader/package/deposit/tasks.py b/swh/loader/package/deposit/tasks.py
--- a/swh/loader/package/deposit/tasks.py
+++ b/swh/loader/package/deposit/tasks.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2019  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -11,4 +11,4 @@
 @shared_task(name=__name__ + ".LoadDeposit")
 def load_deposit(*, url, deposit_id):
     """Load Deposit artifacts"""
-    return DepositLoader(url, deposit_id).load()
+    return DepositLoader.from_configfile(url=url, deposit_id=deposit_id).load()
diff --git a/swh/loader/package/deposit/tests/conftest.py b/swh/loader/package/deposit/tests/conftest.py
--- a/swh/loader/package/deposit/tests/conftest.py
+++ b/swh/loader/package/deposit/tests/conftest.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2019-2020  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -8,6 +8,8 @@
 
 import pytest
 
+from swh.loader.package.deposit.loader import ApiClient
+
 
 @pytest.fixture
 def swh_loader_config(swh_loader_config) -> Dict[str, Any]:
@@ -21,3 +23,8 @@
         }
     )
     return config
+
+
+@pytest.fixture
+def deposit_client(swh_loader_config):
+    return ApiClient(**swh_loader_config["deposit"])
diff --git a/swh/loader/package/deposit/tests/test_deposit.py b/swh/loader/package/deposit/tests/test_deposit.py
--- a/swh/loader/package/deposit/tests/test_deposit.py
+++ b/swh/loader/package/deposit/tests/test_deposit.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2019-2020  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -11,7 +11,7 @@
 import pytest
 
 from swh.core.pytest_plugin import requests_mock_datadir_factory
-from swh.loader.package.deposit.loader import DepositLoader
+from swh.loader.package.deposit.loader import ApiClient, DepositLoader
 from swh.loader.package.loader import now
 from swh.loader.package.tests.common import check_metadata_paths
 from swh.loader.tests import assert_last_visit_matches, check_snapshot, get_stats
@@ -41,17 +41,30 @@
     return requests_mock_datadir
 
 
-def test_deposit_init_ok(swh_config, swh_loader_config):
+def test_deposit_init_ok(swh_storage, deposit_client, swh_loader_config):
     url = "some-url"
     deposit_id = 999
-    loader = DepositLoader(url, deposit_id)  # Something that does not exist
+    loader = DepositLoader(
+        swh_storage, url, deposit_id, deposit_client
+    )  # Something that does not exist
 
     assert loader.url == url
     assert loader.client is not None
     assert loader.client.base_url == swh_loader_config["deposit"]["url"]
 
 
-def test_deposit_loading_unknown_deposit(swh_config, requests_mock_datadir):
+def test_deposit_from_configfile(swh_config):
+    """Ensure the deposit instantiation is ok
+
+    """
+    loader = DepositLoader.from_configfile(url="some-url", deposit_id="666")
+
+    assert isinstance(loader.client, ApiClient)
+
+
+def test_deposit_loading_unknown_deposit(
+    swh_storage, deposit_client, requests_mock_datadir
+):
     """Loading an unknown deposit should fail
 
     no origin, no visit, no snapshot
@@ -59,7 +72,9 @@
     # private api url form: 'https://deposit.s.o/1/private/hal/666/raw/'
     url = "some-url"
     unknown_deposit_id = 667
-    loader = DepositLoader(url, unknown_deposit_id)  # does not exist
+    loader = DepositLoader(
+        swh_storage, url, unknown_deposit_id, deposit_client
+    )  # does not exist
 
     actual_load_status = loader.load()
     assert actual_load_status == {"status": "failed"}
@@ -84,7 +99,7 @@
 
 
 def test_deposit_loading_failure_to_retrieve_1_artifact(
-    swh_config, requests_mock_datadir_missing_one
+    swh_storage, deposit_client, requests_mock_datadir_missing_one
 ):
     """Deposit with missing artifact ends up with an uneventful/partial visit
 
@@ -92,7 +107,7 @@
     # private api url form: 'https://deposit.s.o/1/private/hal/666/raw/'
     url = "some-url-2"
     deposit_id = 666
-    loader = DepositLoader(url, deposit_id)
+    loader = DepositLoader(swh_storage, url, deposit_id, deposit_client)
 
     actual_load_status = loader.load()
     assert actual_load_status["status"] == "uneventful"
@@ -113,10 +128,12 @@
     } == stats
 
 
-def test_revision_metadata_structure(swh_config, requests_mock_datadir):
+def test_deposit_revision_metadata_structure(
+    swh_storage, deposit_client, requests_mock_datadir
+):
     url = "https://hal-test.archives-ouvertes.fr/some-external-id"
     deposit_id = 666
-    loader = DepositLoader(url, deposit_id)
+    loader = DepositLoader(swh_storage, url, deposit_id, deposit_client)
 
     actual_load_status = loader.load()
     assert actual_load_status["status"] == "eventful"
@@ -145,10 +162,10 @@
         )
 
 
-def test_deposit_loading_ok(swh_config, requests_mock_datadir):
+def test_deposit_loading_ok(swh_storage, deposit_client, requests_mock_datadir):
     url = "https://hal-test.archives-ouvertes.fr/some-external-id"
     deposit_id = 666
-    loader = DepositLoader(url, deposit_id)
+    loader = DepositLoader(swh_storage, url, deposit_id, deposit_client)
 
     actual_load_status = loader.load()
     expected_snapshot_id = "b2b327b33dc85818bd23c3ccda8b7e675a66ecbd"
@@ -244,14 +261,14 @@
     assert body == expected_body
 
 
-def test_deposit_loading_ok_2(swh_config, requests_mock_datadir):
+def test_deposit_loading_ok_2(swh_storage, deposit_client, requests_mock_datadir):
     """Field dates should be se appropriately
 
     """
     external_id = "some-external-id"
     url = f"https://hal-test.archives-ouvertes.fr/{external_id}"
     deposit_id = 777
-    loader = DepositLoader(url, deposit_id)
+    loader = DepositLoader(swh_storage, url, deposit_id, deposit_client)
 
     actual_load_status = loader.load()
     expected_snapshot_id = "3e68440fdd7c81d283f8f3aebb6f0c8657864192"
diff --git a/swh/loader/package/deposit/tests/test_tasks.py b/swh/loader/package/deposit/tests/test_tasks.py
--- a/swh/loader/package/deposit/tests/test_tasks.py
+++ b/swh/loader/package/deposit/tests/test_tasks.py
@@ -1,21 +1,24 @@
-# Copyright (C) 2019  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 
-def test_deposit_loader(
+def test_tasks_deposit_loader(
     mocker, swh_scheduler_celery_app, swh_scheduler_celery_worker, swh_config
 ):
-    mock_loader = mocker.patch("swh.loader.package.deposit.loader.DepositLoader.load")
-    mock_loader.return_value = {"status": "eventful"}
+    mock_loader = mocker.patch(
+        "swh.loader.package.deposit.loader.DepositLoader.from_configfile"
+    )
+    mock_loader.return_value = mock_loader
+    mock_loader.load.return_value = {"status": "eventful"}
 
     res = swh_scheduler_celery_app.send_task(
         "swh.loader.package.deposit.tasks.LoadDeposit",
-        kwargs={"url": "some-url", "deposit_id": "some-d-id",},
+        kwargs=dict(url="some-url", deposit_id="some-d-id",),
     )
     assert res
     res.wait()
     assert res.successful()
-
+    assert mock_loader.called
     assert res.result == {"status": "eventful"}
diff --git a/swh/loader/package/loader.py b/swh/loader/package/loader.py
--- a/swh/loader/package/loader.py
+++ b/swh/loader/package/loader.py
@@ -27,8 +27,8 @@
 import attr
 import sentry_sdk
 
-from swh.core.config import load_from_envvar
 from swh.core.tarball import uncompress
+from swh.loader.core.loader import Loader
 from swh.loader.exception import NotFound
 from swh.loader.package.utils import download
 from swh.model import from_disk
@@ -49,7 +49,6 @@
     Snapshot,
     TargetType,
 )
-from swh.storage import get_storage
 from swh.storage.algos.snapshot import snapshot_get_latest
 from swh.storage.interface import StorageInterface
 from swh.storage.utils import now
@@ -118,42 +117,27 @@
 TPackageInfo = TypeVar("TPackageInfo", bound=BasePackageInfo)
 
 
-DEFAULT_CONFIG = {
-    "max_content_size": 100 * 1024 * 1024,
-    "create_authorities": True,
-    "create_fetchers": True,
-}
-
-
-class PackageLoader(Generic[TPackageInfo]):
+class PackageLoader(Loader, Generic[TPackageInfo]):
     # Origin visit type (str) set by the loader
     visit_type = ""
 
-    def __init__(self, url):
+    def __init__(
+        self,
+        storage: StorageInterface,
+        url: str,
+        max_content_size: Optional[int] = None,
+    ):
         """Loader's constructor. This raises exception if the minimal required
            configuration is missing (cf. fn:`check` method).
 
         Args:
-            url (str): Origin url to load data from
+            storage: Storage instance
+            url: Origin url to load data from
 
         """
-        # This expects to use the environment variable SWH_CONFIG_FILENAME
-        self.config = load_from_envvar(DEFAULT_CONFIG)
-        self._check_configuration()
-        self.storage: StorageInterface = get_storage(**self.config["storage"])
+        super().__init__(storage=storage, max_content_size=max_content_size)
         self.url = url
         self.visit_date = datetime.datetime.now(tz=datetime.timezone.utc)
-        self.max_content_size = self.config["max_content_size"]
-
-    def _check_configuration(self):
-        """Checks the minimal configuration required is set for the loader.
-
-        If some required configuration is missing, exception detailing the
-        issue is raised.
-
-        """
-        if "storage" not in self.config:
-            raise ValueError("Misconfiguration, at least the storage key should be set")
 
     def get_versions(self) -> Sequence[str]:
         """Return the list of all published package versions.
diff --git a/swh/loader/package/nixguix/loader.py b/swh/loader/package/nixguix/loader.py
--- a/swh/loader/package/nixguix/loader.py
+++ b/swh/loader/package/nixguix/loader.py
@@ -28,6 +28,7 @@
     Snapshot,
     TargetType,
 )
+from swh.storage.interface import StorageInterface
 
 logger = logging.getLogger(__name__)
 
@@ -58,9 +59,15 @@
 
     visit_type = "nixguix"
 
-    def __init__(self, url):
-        super().__init__(url=url)
+    def __init__(
+        self,
+        storage: StorageInterface,
+        url: str,
+        unsupported_file_extensions: List[str] = [],
+    ):
+        super().__init__(storage=storage, url=url)
         self.provider_url = url
+        self.unsupported_file_extensions = unsupported_file_extensions
 
     # Note: this could be renamed get_artifacts in the PackageLoader
     # base class.
@@ -71,8 +78,9 @@
     @cached_method
     def supported_sources(self):
         raw_sources = self.raw_sources()
-        unsupported_file_extensions = self.config.get("unsupported_file_extensions", [])
-        return clean_sources(parse_sources(raw_sources), unsupported_file_extensions)
+        return clean_sources(
+            parse_sources(raw_sources), self.unsupported_file_extensions
+        )
 
     @cached_method
     def integrity_by_url(self) -> Dict[str, Any]:
diff --git a/swh/loader/package/nixguix/tasks.py b/swh/loader/package/nixguix/tasks.py
--- a/swh/loader/package/nixguix/tasks.py
+++ b/swh/loader/package/nixguix/tasks.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2020  The Software Heritage developers
+# Copyright (C) 2020-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -11,4 +11,4 @@
 @shared_task(name=__name__ + ".LoadNixguix")
 def load_nixguix(*, url=None):
     """Load functional (e.g. guix/nix) package"""
-    return NixGuixLoader(url).load()
+    return NixGuixLoader.from_configfile(url=url).load()
diff --git a/swh/loader/package/nixguix/tests/test_nixguix.py b/swh/loader/package/nixguix/tests/test_nixguix.py
--- a/swh/loader/package/nixguix/tests/test_nixguix.py
+++ b/swh/loader/package/nixguix/tests/test_nixguix.py
@@ -100,13 +100,13 @@
         assert "integrity" in raw
 
 
-def test_retrieve_sources(swh_config, requests_mock_datadir):
+def test_retrieve_sources(swh_storage, requests_mock_datadir):
     j = parse_sources(retrieve_sources(sources_url))
     assert "sources" in j.keys()
     assert len(j["sources"]) == 2
 
 
-def test_nixguix_url_not_found(swh_config, requests_mock_datadir):
+def test_nixguix_url_not_found(swh_storage, requests_mock_datadir):
     """When failing to read from the url, the visit is marked as not_found.
 
     Here the sources url does not exist, so requests_mock_datadir returns a 404.
@@ -117,21 +117,21 @@
 
     """
     unknown_url = "https://non-existing-url/"
-    loader = NixGuixLoader(unknown_url)
+    loader = NixGuixLoader(swh_storage, unknown_url)
     # during the retrieval step
     load_status = loader.load()
 
     assert load_status == {"status": "failed"}
 
     assert_last_visit_matches(
-        loader.storage, unknown_url, status="not_found", type="nixguix", snapshot=None
+        swh_storage, unknown_url, status="not_found", type="nixguix", snapshot=None
     )
 
     assert len(requests_mock_datadir.request_history) == 1
     assert requests_mock_datadir.request_history[0].url == unknown_url
 
 
-def test_nixguix_url_with_decoding_error(swh_config, requests_mock_datadir):
+def test_nixguix_url_with_decoding_error(swh_storage, requests_mock_datadir):
     """Other errors during communication with the url, the visit is marked as failed
 
     requests_mock_datadir will intercept the requests to sources_url. Since the file
@@ -140,26 +140,26 @@
 
     """
     sources_url = "https://example.com/file.txt"
-    loader = NixGuixLoader(sources_url)
+    loader = NixGuixLoader(swh_storage, sources_url)
     load_status = loader.load()
 
     assert load_status == {"status": "failed"}
 
     assert_last_visit_matches(
-        loader.storage, sources_url, status="failed", type="nixguix", snapshot=None
+        swh_storage, sources_url, status="failed", type="nixguix", snapshot=None
     )
 
     assert len(requests_mock_datadir.request_history) == 1
     assert requests_mock_datadir.request_history[0].url == sources_url
 
 
-def test_clean_sources_invalid_schema(swh_config, requests_mock_datadir):
+def test_clean_sources_invalid_schema(swh_storage, requests_mock_datadir):
     sources = {}
     with pytest.raises(ValueError, match="sources structure invalid, missing: .*"):
         clean_sources(sources)
 
 
-def test_clean_sources_invalid_version(swh_config, requests_mock_datadir):
+def test_clean_sources_invalid_version(swh_storage, requests_mock_datadir):
     for version_ok in [1, "1"]:  # Check those versions are fine
         clean_sources({"version": version_ok, "sources": [], "revision": "my-revision"})
 
@@ -172,7 +172,7 @@
             )
 
 
-def test_clean_sources_invalid_sources(swh_config, requests_mock_datadir):
+def test_clean_sources_invalid_sources(swh_storage, requests_mock_datadir):
     valid_sources = [
         # 1 valid source
         {"type": "url", "urls": ["my-url.tar.gz"], "integrity": "my-integrity"},
@@ -218,7 +218,7 @@
         assert actual_match
 
 
-def test_clean_sources_unsupported_artifacts(swh_config, requests_mock_datadir):
+def test_clean_sources_unsupported_artifacts(swh_storage, requests_mock_datadir):
     unsupported_file_extensions = [
         "iso",
         "whl",
@@ -278,12 +278,12 @@
     assert len(clean["sources"]) == len(supported_sources)
 
 
-def test_loader_one_visit(swh_config, requests_mock_datadir, raw_sources):
-    loader = NixGuixLoader(sources_url)
+def test_loader_one_visit(swh_storage, requests_mock_datadir, raw_sources):
+    loader = NixGuixLoader(swh_storage, sources_url)
     res = loader.load()
     assert res["status"] == "eventful"
 
-    stats = get_stats(loader.storage)
+    stats = get_stats(swh_storage)
     assert {
         "content": 1,
         "directory": 3,
@@ -298,10 +298,10 @@
     # The visit is partial because urls pointing to non tarball file
     # are not handled yet
     assert_last_visit_matches(
-        loader.storage, sources_url, status="partial", type="nixguix"
+        swh_storage, sources_url, status="partial", type="nixguix"
     )
 
-    visit_status = origin_get_latest_visit_status(loader.storage, sources_url)
+    visit_status = origin_get_latest_visit_status(swh_storage, sources_url)
     snapshot_swhid = SWHID(
         object_type="snapshot", object_id=hash_to_hex(visit_status.snapshot)
     )
@@ -323,12 +323,12 @@
             origin=sources_url,
         )
     ]
-    assert loader.storage.raw_extrinsic_metadata_get(
+    assert swh_storage.raw_extrinsic_metadata_get(
         MetadataTargetType.SNAPSHOT, snapshot_swhid, metadata_authority,
     ) == PagedResult(next_page_token=None, results=expected_metadata,)
 
 
-def test_uncompress_failure(swh_config, requests_mock_datadir):
+def test_uncompress_failure(swh_storage, requests_mock_datadir):
     """Non tarball files are currently not supported and the uncompress
     function fails on such kind of files.
 
@@ -337,7 +337,7 @@
     created (with a status partial since all files are not archived).
 
     """
-    loader = NixGuixLoader(sources_url)
+    loader = NixGuixLoader(swh_storage, sources_url)
     loader_status = loader.load()
 
     sources = loader.supported_sources()["sources"]
@@ -348,30 +348,30 @@
     # The visit is partial because urls pointing to non tarball files
     # are not handled yet
     assert_last_visit_matches(
-        loader.storage, sources_url, status="partial", type="nixguix"
+        swh_storage, sources_url, status="partial", type="nixguix"
     )
 
 
-def test_loader_incremental(swh_config, requests_mock_datadir):
+def test_loader_incremental(swh_storage, requests_mock_datadir):
     """Ensure a second visit do not download artifact already
     downloaded by the previous visit.
 
     """
-    loader = NixGuixLoader(sources_url)
+    loader = NixGuixLoader(swh_storage, sources_url)
     load_status = loader.load()
 
     loader.load()
     assert load_status == {"status": "eventful", "snapshot_id": SNAPSHOT1.id.hex()}
 
     assert_last_visit_matches(
-        loader.storage,
+        swh_storage,
         sources_url,
         status="partial",
         type="nixguix",
         snapshot=SNAPSHOT1.id,
     )
 
-    check_snapshot(SNAPSHOT1, storage=loader.storage)
+    check_snapshot(SNAPSHOT1, storage=swh_storage)
 
     urls = [
         m.url
@@ -384,7 +384,7 @@
     assert len(urls) == 1
 
 
-def test_loader_two_visits(swh_config, requests_mock_datadir_visits):
+def test_loader_two_visits(swh_storage, requests_mock_datadir_visits):
     """To ensure there is only one origin, but two visits, two revisions
     and two snapshots are created.
 
@@ -393,21 +393,21 @@
     another tarball.
 
     """
-    loader = NixGuixLoader(sources_url)
+    loader = NixGuixLoader(swh_storage, sources_url)
     load_status = loader.load()
     assert load_status == {"status": "eventful", "snapshot_id": SNAPSHOT1.id.hex()}
 
     assert_last_visit_matches(
-        loader.storage,
+        swh_storage,
         sources_url,
         status="partial",
         type="nixguix",
         snapshot=SNAPSHOT1.id,
     )
 
-    check_snapshot(SNAPSHOT1, storage=loader.storage)
+    check_snapshot(SNAPSHOT1, storage=swh_storage)
 
-    stats = get_stats(loader.storage)
+    stats = get_stats(swh_storage)
     assert {
         "content": 1,
         "directory": 3,
@@ -419,7 +419,7 @@
         "snapshot": 1,
     } == stats
 
-    loader = NixGuixLoader(sources_url)
+    loader = NixGuixLoader(swh_storage, sources_url)
     load_status = loader.load()
     expected_snapshot_id_hex = "b0bfa75cbd0cc90aac3b9e95fb0f59c731176d97"
     expected_snapshot_id = hash_to_bytes(expected_snapshot_id_hex)
@@ -429,7 +429,7 @@
     }
 
     assert_last_visit_matches(
-        loader.storage,
+        swh_storage,
         sources_url,
         status="partial",
         type="nixguix",
@@ -456,9 +456,9 @@
             ),
         },
     )
-    check_snapshot(expected_snapshot, storage=loader.storage)
+    check_snapshot(expected_snapshot, storage=swh_storage)
 
-    stats = get_stats(loader.storage)
+    stats = get_stats(swh_storage)
     assert {
         "content": 2,
         "directory": 5,
@@ -471,8 +471,8 @@
     } == stats
 
 
-def test_resolve_revision_from(swh_config, requests_mock_datadir, datadir):
-    loader = NixGuixLoader(sources_url)
+def test_resolve_revision_from(swh_storage, requests_mock_datadir, datadir):
+    loader = NixGuixLoader(swh_storage, sources_url)
 
     known_artifacts = {
         "id1": {"extrinsic": {"raw": {"url": "url1", "integrity": "integrity1"}}},
@@ -489,23 +489,23 @@
     assert loader.resolve_revision_from(known_artifacts, p_info) == None  # noqa
 
 
-def test_evaluation_branch(swh_config, requests_mock_datadir):
-    loader = NixGuixLoader(sources_url)
+def test_evaluation_branch(swh_storage, requests_mock_datadir):
+    loader = NixGuixLoader(swh_storage, sources_url)
     res = loader.load()
     assert res["status"] == "eventful"
 
     assert_last_visit_matches(
-        loader.storage,
+        swh_storage,
         sources_url,
         status="partial",
         type="nixguix",
         snapshot=SNAPSHOT1.id,
     )
 
-    check_snapshot(SNAPSHOT1, storage=loader.storage)
+    check_snapshot(SNAPSHOT1, storage=swh_storage)
 
 
-def test_eoferror(swh_config, requests_mock_datadir):
+def test_eoferror(swh_storage, requests_mock_datadir):
     """Load a truncated archive which is invalid to make the uncompress
     function raising the exception EOFError. We then check if a
     snapshot is created, meaning this error is well managed.
@@ -514,7 +514,7 @@
     sources = (
         "https://nix-community.github.io/nixpkgs-swh/sources-EOFError.json"  # noqa
     )
-    loader = NixGuixLoader(sources)
+    loader = NixGuixLoader(swh_storage, sources)
     loader.load()
 
     expected_snapshot = Snapshot(
@@ -527,7 +527,7 @@
         },
     )
 
-    check_snapshot(expected_snapshot, storage=loader.storage)
+    check_snapshot(expected_snapshot, storage=swh_storage)
 
 
 def fake_download(
@@ -550,11 +550,11 @@
     return download(url, dest, hashes, filename, auth)
 
 
-def test_raise_exception(swh_config, requests_mock_datadir, mocker):
+def test_raise_exception(swh_storage, requests_mock_datadir, mocker):
     mock_download = mocker.patch("swh.loader.package.loader.download")
     mock_download.side_effect = fake_download
 
-    loader = NixGuixLoader(sources_url)
+    loader = NixGuixLoader(swh_storage, sources_url)
     res = loader.load()
 
     assert res == {
@@ -562,18 +562,18 @@
         "snapshot_id": SNAPSHOT1.id.hex(),
     }
 
-    check_snapshot(SNAPSHOT1, storage=loader.storage)
+    check_snapshot(SNAPSHOT1, storage=swh_storage)
 
     assert len(mock_download.mock_calls) == 2
 
     # The visit is partial because some artifact downloads failed
     assert_last_visit_matches(
-        loader.storage, sources_url, status="partial", type="nixguix"
+        swh_storage, sources_url, status="partial", type="nixguix"
     )
 
 
 def test_load_nixguix_one_common_artifact_from_other_loader(
-    swh_config, datadir, requests_mock_datadir_visits, caplog
+    swh_storage, datadir, requests_mock_datadir_visits, caplog
 ):
     """Misformatted revision should be caught and logged, then loading continues
 
@@ -593,7 +593,7 @@
             "version": release,
         }
     ]
-    archive_loader = ArchiveLoader(url=gnu_url, artifacts=gnu_artifacts)
+    archive_loader = ArchiveLoader(swh_storage, url=gnu_url, artifacts=gnu_artifacts)
     actual_load_status = archive_loader.load()
     expected_snapshot_id = "c419397fd912039825ebdbea378bc6283f006bf5"
     assert actual_load_status["status"] == "eventful"
@@ -627,16 +627,14 @@
 
     # first visit with a snapshot, ok
     sources_url = "https://nix-community.github.io/nixpkgs-swh/sources_special.json"
-    loader = NixGuixLoader(sources_url)
+    loader = NixGuixLoader(swh_storage, sources_url)
     actual_load_status2 = loader.load()
     assert actual_load_status2["status"] == "eventful"
 
-    assert_last_visit_matches(
-        loader.storage, sources_url, status="full", type="nixguix"
-    )
+    assert_last_visit_matches(swh_storage, sources_url, status="full", type="nixguix")
 
     snapshot_id = actual_load_status2["snapshot_id"]
-    snapshot = snapshot_get_all_branches(loader.storage, hash_to_bytes(snapshot_id))
+    snapshot = snapshot_get_all_branches(swh_storage, hash_to_bytes(snapshot_id))
     assert snapshot
 
     # simulate a snapshot already seen with a revision with the wrong metadata structure
@@ -646,7 +644,7 @@
     ) as last_snapshot:
         # mutate the snapshot to target a revision with the wrong metadata structure
         # snapshot["branches"][artifact_url.encode("utf-8")] = first_revision
-        old_revision = loader.storage.revision_get([first_revision.target])[0]
+        old_revision = swh_storage.revision_get([first_revision.target])[0]
         # assert that revision is not in the right format
         assert old_revision.metadata["extrinsic"]["raw"].get("integrity", {}) == {}
 
@@ -666,25 +664,25 @@
         # a revision written by somebody else (structure different)
         last_snapshot.return_value = snapshot
 
-        loader = NixGuixLoader(sources_url)
+        loader = NixGuixLoader(swh_storage, sources_url)
         actual_load_status3 = loader.load()
         assert last_snapshot.called
         assert actual_load_status3["status"] == "eventful"
 
         assert_last_visit_matches(
-            loader.storage, sources_url, status="full", type="nixguix"
+            swh_storage, sources_url, status="full", type="nixguix"
         )
 
         new_snapshot_id = "32ff641e510aceefc3a6d0dcbf208b2854d2e965"
         assert actual_load_status3["snapshot_id"] == new_snapshot_id
 
         last_snapshot = snapshot_get_all_branches(
-            loader.storage, hash_to_bytes(new_snapshot_id)
+            swh_storage, hash_to_bytes(new_snapshot_id)
         )
         new_revision_branch = last_snapshot.branches[artifact_url.encode("utf-8")]
         assert new_revision_branch.target_type == TargetType.REVISION
 
-        new_revision = loader.storage.revision_get([new_revision_branch.target])[0]
+        new_revision = swh_storage.revision_get([new_revision_branch.target])[0]
 
         # the new revision has the correct structure,  so it got ingested alright by the
         # new run
diff --git a/swh/loader/package/nixguix/tests/test_tasks.py b/swh/loader/package/nixguix/tests/test_tasks.py
--- a/swh/loader/package/nixguix/tests/test_tasks.py
+++ b/swh/loader/package/nixguix/tests/test_tasks.py
@@ -1,23 +1,17 @@
-# Copyright (C) 2020  The Software Heritage developers
+# Copyright (C) 2020-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
-import json
 
-
-def test_nixguix_loader(
+def test_tasks_nixguix_loader(
     mocker, swh_scheduler_celery_app, swh_scheduler_celery_worker, swh_config
 ):
-    mock_loader = mocker.patch("swh.loader.package.nixguix.loader.NixGuixLoader.load")
-    mock_loader.return_value = {"status": "eventful"}
-
-    mock_retrieve_sources = mocker.patch(
-        "swh.loader.package.nixguix.loader.retrieve_sources"
+    mock_loader = mocker.patch(
+        "swh.loader.package.nixguix.loader.NixGuixLoader.from_configfile"
     )
-    mock_retrieve_sources.return_value = json.dumps(
-        {"version": 1, "sources": [], "revision": "some-revision",}
-    ).encode()
+    mock_loader.return_value = mock_loader
+    mock_loader.load.return_value = {"status": "eventful"}
 
     res = swh_scheduler_celery_app.send_task(
         "swh.loader.package.nixguix.tasks.LoadNixguix", kwargs=dict(url="some-url")
@@ -25,5 +19,5 @@
     assert res
     res.wait()
     assert res.successful()
-
+    assert mock_loader.called
     assert res.result == {"status": "eventful"}
diff --git a/swh/loader/package/npm/loader.py b/swh/loader/package/npm/loader.py
--- a/swh/loader/package/npm/loader.py
+++ b/swh/loader/package/npm/loader.py
@@ -28,6 +28,7 @@
     Sha1Git,
     TimestampWithTimezone,
 )
+from swh.storage.interface import StorageInterface
 
 logger = logging.getLogger(__name__)
 
@@ -86,13 +87,18 @@
 
     visit_type = "npm"
 
-    def __init__(self, url: str):
+    def __init__(
+        self,
+        storage: StorageInterface,
+        url: str,
+        max_content_size: Optional[int] = None,
+    ):
         """Constructor
 
         Args
             str: origin url (e.g. https://www.npmjs.com/package/<package-name>)
         """
-        super().__init__(url=url)
+        super().__init__(storage=storage, url=url, max_content_size=max_content_size)
         package_name = url.split("https://www.npmjs.com/package/")[1]
         safe_name = quote(package_name, safe="")
         self.provider_url = f"https://replicate.npmjs.com/{safe_name}/"
diff --git a/swh/loader/package/npm/tasks.py b/swh/loader/package/npm/tasks.py
--- a/swh/loader/package/npm/tasks.py
+++ b/swh/loader/package/npm/tasks.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2019  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -11,4 +11,4 @@
 @shared_task(name=__name__ + ".LoadNpm")
 def load_npm(*, url: str):
     """Load Npm package"""
-    return NpmLoader(url).load()
+    return NpmLoader.from_configfile(url=url).load()
diff --git a/swh/loader/package/npm/tests/test_npm.py b/swh/loader/package/npm/tests/test_npm.py
--- a/swh/loader/package/npm/tests/test_npm.py
+++ b/swh/loader/package/npm/tests/test_npm.py
@@ -66,7 +66,7 @@
         assert _author_str(author) == expected_author
 
 
-def test_extract_npm_package_author(datadir):
+def test_npm_extract_npm_package_author(datadir):
     package_metadata_filepath = os.path.join(
         datadir, "https_replicate.npmjs.com", "org_visit1"
     )
@@ -305,16 +305,16 @@
     return "https://replicate.npmjs.com/%s/" % package
 
 
-def test_revision_metadata_structure(swh_config, requests_mock_datadir):
+def test_npm_revision_metadata_structure(swh_storage, requests_mock_datadir):
     package = "org"
-    loader = NpmLoader(package_url(package))
+    loader = NpmLoader(swh_storage, package_url(package))
 
     actual_load_status = loader.load()
     assert actual_load_status["status"] == "eventful"
     assert actual_load_status["snapshot_id"] is not None
 
     expected_revision_id = hash_to_bytes("d8a1c7474d2956ac598a19f0f27d52f7015f117e")
-    revision = loader.storage.revision_get([expected_revision_id])[0]
+    revision = swh_storage.revision_get([expected_revision_id])[0]
     assert revision is not None
 
     check_metadata_paths(
@@ -336,10 +336,10 @@
         )
 
 
-def test_npm_loader_first_visit(swh_config, requests_mock_datadir, org_api_info):
+def test_npm_loader_first_visit(swh_storage, requests_mock_datadir, org_api_info):
     package = "org"
     url = package_url(package)
-    loader = NpmLoader(url)
+    loader = NpmLoader(swh_storage, url)
 
     actual_load_status = loader.load()
     expected_snapshot_id = hash_to_bytes("d0587e1195aed5a8800411a008f2f2d627f18e2d")
@@ -349,10 +349,10 @@
     }
 
     assert_last_visit_matches(
-        loader.storage, url, status="full", type="npm", snapshot=expected_snapshot_id
+        swh_storage, url, status="full", type="npm", snapshot=expected_snapshot_id
     )
 
-    stats = get_stats(loader.storage)
+    stats = get_stats(swh_storage)
 
     assert {
         "content": len(_expected_new_contents_first_visit),
@@ -365,18 +365,15 @@
         "snapshot": 1,
     } == stats
 
-    contents = loader.storage.content_get(_expected_new_contents_first_visit)
+    contents = swh_storage.content_get(_expected_new_contents_first_visit)
     count = sum(0 if content is None else 1 for content in contents)
     assert count == len(_expected_new_contents_first_visit)
 
     assert (
-        list(loader.storage.directory_missing(_expected_new_directories_first_visit))
-        == []
+        list(swh_storage.directory_missing(_expected_new_directories_first_visit)) == []
     )
 
-    assert (
-        list(loader.storage.revision_missing(_expected_new_revisions_first_visit)) == []
-    )
+    assert list(swh_storage.revision_missing(_expected_new_revisions_first_visit)) == []
 
     versions = [
         ("0.0.2", "d8a1c7474d2956ac598a19f0f27d52f7015f117e"),
@@ -399,14 +396,14 @@
             },
         },
     )
-    check_snapshot(expected_snapshot, loader.storage)
+    check_snapshot(expected_snapshot, swh_storage)
 
     metadata_authority = MetadataAuthority(
         type=MetadataAuthorityType.FORGE, url="https://npmjs.com/",
     )
 
     for (version_name, revision_id) in versions:
-        revision = loader.storage.revision_get([hash_to_bytes(revision_id)])[0]
+        revision = swh_storage.revision_get([hash_to_bytes(revision_id)])[0]
         directory_id = revision.directory
         directory_swhid = SWHID(object_type="directory", object_id=directory_id,)
         revision_swhid = SWHID(object_type="revision", object_id=revision_id,)
@@ -427,15 +424,15 @@
                 revision=revision_swhid,
             )
         ]
-        assert loader.storage.raw_extrinsic_metadata_get(
+        assert swh_storage.raw_extrinsic_metadata_get(
             MetadataTargetType.DIRECTORY, directory_swhid, metadata_authority,
         ) == PagedResult(next_page_token=None, results=expected_metadata,)
 
 
-def test_npm_loader_incremental_visit(swh_config, requests_mock_datadir_visits):
+def test_npm_loader_incremental_visit(swh_storage, requests_mock_datadir_visits):
     package = "org"
     url = package_url(package)
-    loader = NpmLoader(url)
+    loader = NpmLoader(swh_storage, url)
 
     expected_snapshot_id = hash_to_bytes("d0587e1195aed5a8800411a008f2f2d627f18e2d")
     actual_load_status = loader.load()
@@ -444,10 +441,10 @@
         "snapshot_id": expected_snapshot_id.hex(),
     }
     assert_last_visit_matches(
-        loader.storage, url, status="full", type="npm", snapshot=expected_snapshot_id
+        swh_storage, url, status="full", type="npm", snapshot=expected_snapshot_id
     )
 
-    stats = get_stats(loader.storage)
+    stats = get_stats(swh_storage)
 
     assert {
         "content": len(_expected_new_contents_first_visit),
@@ -470,9 +467,9 @@
     assert snap_id2 is not None
     assert snap_id2 != actual_load_status["snapshot_id"]
 
-    assert_last_visit_matches(loader.storage, url, status="full", type="npm")
+    assert_last_visit_matches(swh_storage, url, status="full", type="npm")
 
-    stats = get_stats(loader.storage)
+    stats = get_stats(swh_storage)
 
     assert {  # 3 new releases artifacts
         "content": len(_expected_new_contents_first_visit) + 14,
@@ -494,10 +491,10 @@
 
 
 @pytest.mark.usefixtures("requests_mock_datadir")
-def test_npm_loader_version_divergence(swh_config):
+def test_npm_loader_version_divergence(swh_storage):
     package = "@aller_shared"
     url = package_url(package)
-    loader = NpmLoader(url)
+    loader = NpmLoader(swh_storage, url)
 
     actual_load_status = loader.load()
     expected_snapshot_id = hash_to_bytes("b11ebac8c9d0c9e5063a2df693a18e3aba4b2f92")
@@ -506,10 +503,10 @@
         "snapshot_id": expected_snapshot_id.hex(),
     }
     assert_last_visit_matches(
-        loader.storage, url, status="full", type="npm", snapshot=expected_snapshot_id
+        swh_storage, url, status="full", type="npm", snapshot=expected_snapshot_id
     )
 
-    stats = get_stats(loader.storage)
+    stats = get_stats(swh_storage)
 
     assert {  # 1 new releases artifacts
         "content": 534,
@@ -538,7 +535,7 @@
             ),
         },
     )
-    check_snapshot(expected_snapshot, loader.storage)
+    check_snapshot(expected_snapshot, swh_storage)
 
 
 def test_npm_artifact_to_revision_id_none():
@@ -602,13 +599,13 @@
     )
 
 
-def test_npm_artifact_with_no_intrinsic_metadata(swh_config, requests_mock_datadir):
+def test_npm_artifact_with_no_intrinsic_metadata(swh_storage, requests_mock_datadir):
     """Skip artifact with no intrinsic metadata during ingestion
 
     """
     package = "nativescript-telerik-analytics"
     url = package_url(package)
-    loader = NpmLoader(url)
+    loader = NpmLoader(swh_storage, url)
 
     actual_load_status = loader.load()
     # no branch as one artifact without any intrinsic metadata
@@ -620,20 +617,20 @@
         "snapshot_id": expected_snapshot.id.hex(),
     }
 
-    check_snapshot(expected_snapshot, loader.storage)
+    check_snapshot(expected_snapshot, swh_storage)
 
     assert_last_visit_matches(
-        loader.storage, url, status="full", type="npm", snapshot=expected_snapshot.id
+        swh_storage, url, status="full", type="npm", snapshot=expected_snapshot.id
     )
 
 
-def test_npm_artifact_with_no_upload_time(swh_config, requests_mock_datadir):
+def test_npm_artifact_with_no_upload_time(swh_storage, requests_mock_datadir):
     """With no time upload, artifact is skipped
 
     """
     package = "jammit-no-time"
     url = package_url(package)
-    loader = NpmLoader(url)
+    loader = NpmLoader(swh_storage, url)
 
     actual_load_status = loader.load()
     # no branch as one artifact without any intrinsic metadata
@@ -645,20 +642,20 @@
         "snapshot_id": expected_snapshot.id.hex(),
     }
 
-    check_snapshot(expected_snapshot, loader.storage)
+    check_snapshot(expected_snapshot, swh_storage)
 
     assert_last_visit_matches(
-        loader.storage, url, status="partial", type="npm", snapshot=expected_snapshot.id
+        swh_storage, url, status="partial", type="npm", snapshot=expected_snapshot.id
     )
 
 
-def test_npm_artifact_use_mtime_if_no_time(swh_config, requests_mock_datadir):
+def test_npm_artifact_use_mtime_if_no_time(swh_storage, requests_mock_datadir):
     """With no time upload, artifact is skipped
 
     """
     package = "jammit-express"
     url = package_url(package)
-    loader = NpmLoader(url)
+    loader = NpmLoader(swh_storage, url)
 
     actual_load_status = loader.load()
     expected_snapshot_id = hash_to_bytes("d6e08e19159f77983242877c373c75222d5ae9dd")
@@ -681,34 +678,34 @@
             ),
         },
     )
-    check_snapshot(expected_snapshot, loader.storage)
+    check_snapshot(expected_snapshot, swh_storage)
 
     assert_last_visit_matches(
-        loader.storage, url, status="full", type="npm", snapshot=expected_snapshot.id
+        swh_storage, url, status="full", type="npm", snapshot=expected_snapshot.id
     )
 
 
-def test_npm_no_artifact(swh_config, requests_mock_datadir):
+def test_npm_no_artifact(swh_storage, requests_mock_datadir):
     """If no artifacts at all is found for origin, the visit fails completely
 
     """
     package = "catify"
     url = package_url(package)
-    loader = NpmLoader(url)
+    loader = NpmLoader(swh_storage, url)
     actual_load_status = loader.load()
     assert actual_load_status == {
         "status": "failed",
     }
 
-    assert_last_visit_matches(loader.storage, url, status="failed", type="npm")
+    assert_last_visit_matches(swh_storage, url, status="failed", type="npm")
 
 
-def test_npm_origin_not_found(swh_config, requests_mock_datadir):
+def test_npm_origin_not_found(swh_storage, requests_mock_datadir):
     url = package_url("non-existent-url")
-    loader = NpmLoader(url)
+    loader = NpmLoader(swh_storage, url)
 
     assert loader.load() == {"status": "failed"}
 
     assert_last_visit_matches(
-        loader.storage, url, status="not_found", type="npm", snapshot=None
+        swh_storage, url, status="not_found", type="npm", snapshot=None
     )
diff --git a/swh/loader/package/npm/tests/test_tasks.py b/swh/loader/package/npm/tests/test_tasks.py
--- a/swh/loader/package/npm/tests/test_tasks.py
+++ b/swh/loader/package/npm/tests/test_tasks.py
@@ -1,14 +1,14 @@
-# Copyright (C) 2019  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 
-def test_npm_loader(
+def test_tasks_npm_loader(
     mocker, swh_scheduler_celery_app, swh_scheduler_celery_worker, swh_config
 ):
-    mock_loader = mocker.patch("swh.loader.package.npm.loader.NpmLoader.load")
-    mock_loader.return_value = {"status": "eventful"}
+    mock_load = mocker.patch("swh.loader.package.npm.loader.NpmLoader.load")
+    mock_load.return_value = {"status": "eventful"}
 
     res = swh_scheduler_celery_app.send_task(
         "swh.loader.package.npm.tasks.LoadNpm",
@@ -17,5 +17,5 @@
     assert res
     res.wait()
     assert res.successful()
-
+    assert mock_load.called
     assert res.result == {"status": "eventful"}
diff --git a/swh/loader/package/pypi/loader.py b/swh/loader/package/pypi/loader.py
--- a/swh/loader/package/pypi/loader.py
+++ b/swh/loader/package/pypi/loader.py
@@ -27,6 +27,7 @@
     Sha1Git,
     TimestampWithTimezone,
 )
+from swh.storage.interface import StorageInterface
 
 logger = logging.getLogger(__name__)
 
@@ -63,8 +64,13 @@
 
     visit_type = "pypi"
 
-    def __init__(self, url):
-        super().__init__(url=url)
+    def __init__(
+        self,
+        storage: StorageInterface,
+        url: str,
+        max_content_size: Optional[int] = None,
+    ):
+        super().__init__(storage=storage, url=url, max_content_size=max_content_size)
         self.provider_url = pypi_api_url(self.url)
 
     @cached_method
diff --git a/swh/loader/package/pypi/tasks.py b/swh/loader/package/pypi/tasks.py
--- a/swh/loader/package/pypi/tasks.py
+++ b/swh/loader/package/pypi/tasks.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2019  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -11,4 +11,4 @@
 @shared_task(name=__name__ + ".LoadPyPI")
 def load_pypi(*, url=None):
     """Load PyPI package"""
-    return PyPILoader(url).load()
+    return PyPILoader.from_configfile(url=url).load()
diff --git a/swh/loader/package/pypi/tests/test_pypi.py b/swh/loader/package/pypi/tests/test_pypi.py
--- a/swh/loader/package/pypi/tests/test_pypi.py
+++ b/swh/loader/package/pypi/tests/test_pypi.py
@@ -3,14 +3,12 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
-import copy
 import json
 import os
 from os import path
 from unittest.mock import patch
 
 import pytest
-import yaml
 
 from swh.core.pytest_plugin import requests_mock_datadir_factory
 from swh.core.tarball import uncompress
@@ -48,7 +46,7 @@
         return f.read()
 
 
-def test_author_basic():
+def test_pypi_author_basic():
     data = {
         "author": "i-am-groot",
         "author_email": "iam@groot.org",
@@ -64,7 +62,7 @@
     assert actual_author == expected_author
 
 
-def test_author_empty_email():
+def test_pypi_author_empty_email():
     data = {
         "author": "i-am-groot",
         "author_email": "",
@@ -76,7 +74,7 @@
     assert actual_author == expected_author
 
 
-def test_author_empty_name():
+def test_pypi_author_empty_name():
     data = {
         "author": "",
         "author_email": "iam@groot.org",
@@ -90,7 +88,7 @@
     assert actual_author == expected_author
 
 
-def test_author_malformed():
+def test_pypi_author_malformed():
     data = {
         "author": "['pierre', 'paul', 'jacques']",
         "author_email": None,
@@ -107,7 +105,7 @@
     assert actual_author == expected_author
 
 
-def test_author_malformed_2():
+def test_pypi_author_malformed_2():
     data = {
         "author": "[marie, jeanne]",
         "author_email": "[marie@some, jeanne@thing]",
@@ -124,7 +122,7 @@
     assert actual_author == expected_author
 
 
-def test_author_malformed_3():
+def test_pypi_author_malformed_3():
     data = {
         "author": "[marie, jeanne, pierre]",
         "author_email": "[marie@somewhere.org, jeanne@somewhere.org]",
@@ -146,20 +144,6 @@
 # configuration error #
 
 
-def test_badly_configured_loader_raise(tmp_path, swh_loader_config, monkeypatch):
-    """Badly configured loader should raise"""
-    wrong_config = copy.deepcopy(swh_loader_config)
-    wrong_config.pop("storage")
-
-    conf_path = os.path.join(str(tmp_path), "loader.yml")
-    with open(conf_path, "w") as f:
-        f.write(yaml.dump(wrong_config))
-    monkeypatch.setenv("SWH_CONFIG_FILENAME", conf_path)
-
-    with pytest.raises(ValueError, match="Misconfiguration"):
-        PyPILoader(url="some-url")
-
-
 def test_pypi_api_url():
     """Compute pypi api url from the pypi project url should be ok"""
     url = pypi_api_url("https://pypi.org/project/requests")
@@ -173,7 +157,7 @@
 
 
 @pytest.mark.fs
-def test_extract_intrinsic_metadata(tmp_path, datadir):
+def test_pypi_extract_intrinsic_metadata(tmp_path, datadir):
     """Parsing existing archive's PKG-INFO should yield results"""
     uncompressed_archive_path = str(tmp_path)
     archive_path = path.join(
@@ -197,7 +181,7 @@
 
 
 @pytest.mark.fs
-def test_extract_intrinsic_metadata_failures(tmp_path):
+def test_pypi_extract_intrinsic_metadata_failures(tmp_path):
     """Parsing inexistent path/archive/PKG-INFO yield None"""
     tmp_path = str(tmp_path)  # py3.5 work around (PosixPath issue)
     # inexistent first level path
@@ -225,18 +209,18 @@
 )
 
 
-def test_no_release_artifact(swh_config, requests_mock_datadir_missing_all):
+def test_pypi_no_release_artifact(swh_storage, requests_mock_datadir_missing_all):
     """Load a pypi project with all artifacts missing ends up with no snapshot
 
     """
     url = "https://pypi.org/project/0805nexter"
-    loader = PyPILoader(url)
+    loader = PyPILoader(swh_storage, url)
 
     actual_load_status = loader.load()
     assert actual_load_status["status"] == "uneventful"
     assert actual_load_status["snapshot_id"] is not None
 
-    stats = get_stats(loader.storage)
+    stats = get_stats(swh_storage)
     assert {
         "content": 0,
         "directory": 0,
@@ -248,10 +232,10 @@
         "snapshot": 1,
     } == stats
 
-    assert_last_visit_matches(loader.storage, url, status="partial", type="pypi")
+    assert_last_visit_matches(swh_storage, url, status="partial", type="pypi")
 
 
-def test_pypi_fail__load_snapshot(swh_config, requests_mock_datadir):
+def test_pypi_fail__load_snapshot(swh_storage, requests_mock_datadir):
     """problem during loading: {visit: failed, status: failed, no snapshot}
 
     """
@@ -260,7 +244,7 @@
         "swh.loader.package.pypi.loader.PyPILoader._load_snapshot",
         side_effect=ValueError("Fake problem to fail visit"),
     ):
-        loader = PyPILoader(url)
+        loader = PyPILoader(swh_storage, url)
 
         actual_load_status = loader.load()
         assert actual_load_status == {"status": "failed"}
@@ -278,25 +262,25 @@
             "snapshot": 0,
         } == stats
 
-        assert_last_visit_matches(loader.storage, url, status="failed", type="pypi")
+        assert_last_visit_matches(swh_storage, url, status="failed", type="pypi")
 
 
 # problem during loading:
 # {visit: partial, status: uneventful, no snapshot}
 
 
-def test_release_with_traceback(swh_config, requests_mock_datadir):
+def test_pypi_release_with_traceback(swh_storage, requests_mock_datadir):
     url = "https://pypi.org/project/0805nexter"
     with patch(
         "swh.loader.package.pypi.loader.PyPILoader.last_snapshot",
         side_effect=ValueError("Fake problem to fail the visit"),
     ):
-        loader = PyPILoader(url)
+        loader = PyPILoader(swh_storage, url)
 
         actual_load_status = loader.load()
         assert actual_load_status == {"status": "failed"}
 
-        stats = get_stats(loader.storage)
+        stats = get_stats(swh_storage)
 
         assert {
             "content": 0,
@@ -309,7 +293,7 @@
             "snapshot": 0,
         } == stats
 
-        assert_last_visit_matches(loader.storage, url, status="failed", type="pypi")
+        assert_last_visit_matches(swh_storage, url, status="failed", type="pypi")
 
 
 # problem during loading: failure early enough in between swh contents...
@@ -333,18 +317,18 @@
 # {visit partial, status: eventful, 1 snapshot}
 
 
-def test_revision_metadata_structure(
-    swh_config, requests_mock_datadir, _0805nexter_api_info
+def test_pypi_revision_metadata_structure(
+    swh_storage, requests_mock_datadir, _0805nexter_api_info
 ):
     url = "https://pypi.org/project/0805nexter"
-    loader = PyPILoader(url)
+    loader = PyPILoader(swh_storage, url)
 
     actual_load_status = loader.load()
     assert actual_load_status["status"] == "eventful"
     assert actual_load_status["snapshot_id"] is not None
 
     expected_revision_id = hash_to_bytes("e445da4da22b31bfebb6ffc4383dbf839a074d21")
-    revision = loader.storage.revision_get([expected_revision_id])[0]
+    revision = swh_storage.revision_get([expected_revision_id])[0]
     assert revision is not None
 
     check_metadata_paths(
@@ -391,17 +375,19 @@
             revision=revision_swhid,
         )
     ]
-    assert loader.storage.raw_extrinsic_metadata_get(
+    assert swh_storage.raw_extrinsic_metadata_get(
         MetadataTargetType.DIRECTORY, directory_swhid, metadata_authority,
     ) == PagedResult(next_page_token=None, results=expected_metadata,)
 
 
-def test_visit_with_missing_artifact(swh_config, requests_mock_datadir_missing_one):
+def test_pypi_visit_with_missing_artifact(
+    swh_storage, requests_mock_datadir_missing_one
+):
     """Load a pypi project with some missing artifacts ends up with 1 snapshot
 
     """
     url = "https://pypi.org/project/0805nexter"
-    loader = PyPILoader(url)
+    loader = PyPILoader(swh_storage, url)
 
     actual_load_status = loader.load()
     expected_snapshot_id = hash_to_bytes("dd0e4201a232b1c104433741dbf45895b8ac9355")
@@ -410,7 +396,7 @@
         "snapshot_id": expected_snapshot_id.hex(),
     }
 
-    stats = get_stats(loader.storage)
+    stats = get_stats(swh_storage)
 
     assert {
         "content": 3,
@@ -432,7 +418,7 @@
         ],
     )
 
-    assert list(loader.storage.content_missing_per_sha1(expected_contents)) == []
+    assert list(swh_storage.content_missing_per_sha1(expected_contents)) == []
 
     expected_dirs = map(
         hash_to_bytes,
@@ -442,7 +428,7 @@
         ],
     )
 
-    assert list(loader.storage.directory_missing(expected_dirs)) == []
+    assert list(swh_storage.directory_missing(expected_dirs)) == []
 
     # {revision hash: directory hash}
     expected_revs = {
@@ -450,7 +436,7 @@
             "b178b66bd22383d5f16f4f5c923d39ca798861b4"
         ),  # noqa
     }
-    assert list(loader.storage.revision_missing(expected_revs)) == []
+    assert list(swh_storage.revision_missing(expected_revs)) == []
 
     expected_snapshot = Snapshot(
         id=hash_to_bytes(expected_snapshot_id),
@@ -464,23 +450,19 @@
             ),
         },
     )
-    check_snapshot(expected_snapshot, storage=loader.storage)
+    check_snapshot(expected_snapshot, storage=swh_storage)
 
     assert_last_visit_matches(
-        loader.storage,
-        url,
-        status="partial",
-        type="pypi",
-        snapshot=expected_snapshot_id,
+        swh_storage, url, status="partial", type="pypi", snapshot=expected_snapshot_id,
     )
 
 
-def test_visit_with_1_release_artifact(swh_config, requests_mock_datadir):
+def test_pypi_visit_with_1_release_artifact(swh_storage, requests_mock_datadir):
     """With no prior visit, load a pypi project ends up with 1 snapshot
 
     """
     url = "https://pypi.org/project/0805nexter"
-    loader = PyPILoader(url)
+    loader = PyPILoader(swh_storage, url)
 
     actual_load_status = loader.load()
     expected_snapshot_id = hash_to_bytes("ba6e158ada75d0b3cfb209ffdf6daa4ed34a227a")
@@ -489,7 +471,7 @@
         "snapshot_id": expected_snapshot_id.hex(),
     }
 
-    stats = get_stats(loader.storage)
+    stats = get_stats(swh_storage)
     assert {
         "content": 6,
         "directory": 4,
@@ -513,7 +495,7 @@
         ],
     )
 
-    assert list(loader.storage.content_missing_per_sha1(expected_contents)) == []
+    assert list(swh_storage.content_missing_per_sha1(expected_contents)) == []
 
     expected_dirs = map(
         hash_to_bytes,
@@ -525,7 +507,7 @@
         ],
     )
 
-    assert list(loader.storage.directory_missing(expected_dirs)) == []
+    assert list(swh_storage.directory_missing(expected_dirs)) == []
 
     # {revision hash: directory hash}
     expected_revs = {
@@ -536,7 +518,7 @@
             "b178b66bd22383d5f16f4f5c923d39ca798861b4"
         ),  # noqa
     }
-    assert list(loader.storage.revision_missing(expected_revs)) == []
+    assert list(swh_storage.revision_missing(expected_revs)) == []
 
     expected_snapshot = Snapshot(
         id=expected_snapshot_id,
@@ -554,19 +536,19 @@
             ),
         },
     )
-    check_snapshot(expected_snapshot, loader.storage)
+    check_snapshot(expected_snapshot, swh_storage)
 
     assert_last_visit_matches(
-        loader.storage, url, status="full", type="pypi", snapshot=expected_snapshot_id
+        swh_storage, url, status="full", type="pypi", snapshot=expected_snapshot_id
     )
 
 
-def test_multiple_visits_with_no_change(swh_config, requests_mock_datadir):
+def test_pypi_multiple_visits_with_no_change(swh_storage, requests_mock_datadir):
     """Multiple visits with no changes results in 1 same snapshot
 
     """
     url = "https://pypi.org/project/0805nexter"
-    loader = PyPILoader(url)
+    loader = PyPILoader(swh_storage, url)
 
     actual_load_status = loader.load()
     snapshot_id = hash_to_bytes("ba6e158ada75d0b3cfb209ffdf6daa4ed34a227a")
@@ -575,10 +557,10 @@
         "snapshot_id": snapshot_id.hex(),
     }
     assert_last_visit_matches(
-        loader.storage, url, status="full", type="pypi", snapshot=snapshot_id
+        swh_storage, url, status="full", type="pypi", snapshot=snapshot_id
     )
 
-    stats = get_stats(loader.storage)
+    stats = get_stats(swh_storage)
 
     assert {
         "content": 6,
@@ -607,7 +589,7 @@
             ),
         },
     )
-    check_snapshot(expected_snapshot, loader.storage)
+    check_snapshot(expected_snapshot, swh_storage)
 
     actual_load_status2 = loader.load()
     assert actual_load_status2 == {
@@ -616,10 +598,10 @@
     }
 
     visit_status2 = assert_last_visit_matches(
-        loader.storage, url, status="full", type="pypi"
+        swh_storage, url, status="full", type="pypi"
     )
 
-    stats2 = get_stats(loader.storage)
+    stats2 = get_stats(swh_storage)
     expected_stats2 = stats.copy()
     expected_stats2["origin_visit"] = 1 + 1
     assert expected_stats2 == stats2
@@ -628,15 +610,15 @@
     assert visit_status2.snapshot == snapshot_id
 
 
-def test_incremental_visit(swh_config, requests_mock_datadir_visits):
+def test_pypi_incremental_visit(swh_storage, requests_mock_datadir_visits):
     """With prior visit, 2nd load will result with a different snapshot
 
     """
     url = "https://pypi.org/project/0805nexter"
-    loader = PyPILoader(url)
+    loader = PyPILoader(swh_storage, url)
 
     visit1_actual_load_status = loader.load()
-    visit1_stats = get_stats(loader.storage)
+    visit1_stats = get_stats(swh_storage)
     expected_snapshot_id = hash_to_bytes("ba6e158ada75d0b3cfb209ffdf6daa4ed34a227a")
     assert visit1_actual_load_status == {
         "status": "eventful",
@@ -644,7 +626,7 @@
     }
 
     assert_last_visit_matches(
-        loader.storage, url, status="full", type="pypi", snapshot=expected_snapshot_id
+        swh_storage, url, status="full", type="pypi", snapshot=expected_snapshot_id
     )
 
     assert {
@@ -663,7 +645,7 @@
     del loader._cached_info
 
     visit2_actual_load_status = loader.load()
-    visit2_stats = get_stats(loader.storage)
+    visit2_stats = get_stats(swh_storage)
 
     assert visit2_actual_load_status["status"] == "eventful", visit2_actual_load_status
     expected_snapshot_id2 = hash_to_bytes("2e5149a7b0725d18231a37b342e9b7c4e121f283")
@@ -673,7 +655,7 @@
     }
 
     assert_last_visit_matches(
-        loader.storage, url, status="full", type="pypi", snapshot=expected_snapshot_id2
+        swh_storage, url, status="full", type="pypi", snapshot=expected_snapshot_id2
     )
 
     assert {
@@ -700,7 +682,7 @@
         ],
     )
 
-    assert list(loader.storage.content_missing_per_sha1(expected_contents)) == []
+    assert list(swh_storage.content_missing_per_sha1(expected_contents)) == []
 
     expected_dirs = map(
         hash_to_bytes,
@@ -714,7 +696,7 @@
         ],
     )
 
-    assert list(loader.storage.directory_missing(expected_dirs)) == []
+    assert list(swh_storage.directory_missing(expected_dirs)) == []
 
     # {revision hash: directory hash}
     expected_revs = {
@@ -729,7 +711,7 @@
         ),  # noqa
     }
 
-    assert list(loader.storage.revision_missing(expected_revs)) == []
+    assert list(swh_storage.revision_missing(expected_revs)) == []
 
     expected_snapshot = Snapshot(
         id=expected_snapshot_id2,
@@ -752,10 +734,10 @@
         },
     )
 
-    check_snapshot(expected_snapshot, loader.storage)
+    check_snapshot(expected_snapshot, swh_storage)
 
     assert_last_visit_matches(
-        loader.storage, url, status="full", type="pypi", snapshot=expected_snapshot.id
+        swh_storage, url, status="full", type="pypi", snapshot=expected_snapshot.id
     )
 
     urls = [
@@ -778,12 +760,12 @@
 # snapshot branch output is different
 
 
-def test_visit_1_release_with_2_artifacts(swh_config, requests_mock_datadir):
+def test_pypi_visit_1_release_with_2_artifacts(swh_storage, requests_mock_datadir):
     """With no prior visit, load a pypi project ends up with 1 snapshot
 
     """
     url = "https://pypi.org/project/nexter"
-    loader = PyPILoader(url)
+    loader = PyPILoader(swh_storage, url)
 
     actual_load_status = loader.load()
     expected_snapshot_id = hash_to_bytes("a27e638a4dad6fbfa273c6ebec1c4bf320fb84c6")
@@ -805,10 +787,10 @@
             ),
         },
     )
-    check_snapshot(expected_snapshot, loader.storage)
+    check_snapshot(expected_snapshot, swh_storage)
 
     assert_last_visit_matches(
-        loader.storage, url, status="full", type="pypi", snapshot=expected_snapshot.id
+        swh_storage, url, status="full", type="pypi", snapshot=expected_snapshot.id
     )
 
 
@@ -883,12 +865,12 @@
     )
 
 
-def test_pypi_artifact_with_no_intrinsic_metadata(swh_config, requests_mock_datadir):
+def test_pypi_artifact_with_no_intrinsic_metadata(swh_storage, requests_mock_datadir):
     """Skip artifact with no intrinsic metadata during ingestion
 
     """
     url = "https://pypi.org/project/upymenu"
-    loader = PyPILoader(url)
+    loader = PyPILoader(swh_storage, url)
 
     actual_load_status = loader.load()
     expected_snapshot_id = hash_to_bytes("1a8893e6a86f444e8be8e7bda6cb34fb1735a00e")
@@ -899,19 +881,19 @@
 
     # no branch as one artifact without any intrinsic metadata
     expected_snapshot = Snapshot(id=expected_snapshot_id, branches={})
-    check_snapshot(expected_snapshot, loader.storage)
+    check_snapshot(expected_snapshot, swh_storage)
 
     assert_last_visit_matches(
-        loader.storage, url, status="full", type="pypi", snapshot=expected_snapshot.id
+        swh_storage, url, status="full", type="pypi", snapshot=expected_snapshot.id
     )
 
 
-def test_pypi_origin_not_found(swh_config, requests_mock_datadir):
+def test_pypi_origin_not_found(swh_storage, requests_mock_datadir):
     url = "https://pypi.org/project/unknown"
-    loader = PyPILoader(url)
+    loader = PyPILoader(swh_storage, url)
 
     assert loader.load() == {"status": "failed"}
 
     assert_last_visit_matches(
-        loader.storage, url, status="not_found", type="pypi", snapshot=None
+        swh_storage, url, status="not_found", type="pypi", snapshot=None
     )
diff --git a/swh/loader/package/pypi/tests/test_tasks.py b/swh/loader/package/pypi/tests/test_tasks.py
--- a/swh/loader/package/pypi/tests/test_tasks.py
+++ b/swh/loader/package/pypi/tests/test_tasks.py
@@ -1,14 +1,14 @@
-# Copyright (C) 2019  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 
-def test_pypi_loader(
+def test_tasks_pypi_loader(
     mocker, swh_scheduler_celery_app, swh_scheduler_celery_worker, swh_config
 ):
-    mock_loader = mocker.patch("swh.loader.package.pypi.loader.PyPILoader.load")
-    mock_loader.return_value = {"status": "eventful"}
+    mock_load = mocker.patch("swh.loader.package.pypi.loader.PyPILoader.load")
+    mock_load.return_value = {"status": "eventful"}
 
     res = swh_scheduler_celery_app.send_task(
         "swh.loader.package.pypi.tasks.LoadPyPI", kwargs=dict(url="some-url")
@@ -16,5 +16,5 @@
     assert res
     res.wait()
     assert res.successful()
-
+    assert mock_load.called
     assert res.result == {"status": "eventful"}
diff --git a/swh/loader/package/tests/test_loader.py b/swh/loader/package/tests/test_loader.py
--- a/swh/loader/package/tests/test_loader.py
+++ b/swh/loader/package/tests/test_loader.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2019-2020  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -25,11 +25,11 @@
         raise ValueError("We refuse to add an origin visit")
 
 
-def test_loader_origin_visit_failure(swh_config):
+def test_loader_origin_visit_failure(swh_storage):
     """Failure to add origin or origin visit should failed immediately
 
     """
-    loader = PackageLoader("some-url")
+    loader = PackageLoader(swh_storage, "some-url")
     loader.storage = FakeStorage()
 
     actual_load_status = loader.load()
@@ -84,4 +84,4 @@
     with pytest.raises(
         AssertionError, match="SWH_CONFIG_FILENAME environment variable is undefined"
     ):
-        DummyPackageLoader(url="some-url")
+        DummyPackageLoader.from_configfile(url="some-url")
diff --git a/swh/loader/package/tests/test_loader_metadata.py b/swh/loader/package/tests/test_loader_metadata.py
--- a/swh/loader/package/tests/test_loader_metadata.py
+++ b/swh/loader/package/tests/test_loader_metadata.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2019-2020  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -27,7 +27,6 @@
     RevisionType,
     Sha1Git,
 )
-from swh.storage import get_storage
 
 EMPTY_SNAPSHOT_ID = "1a8893e6a86f444e8be8e7bda6cb34fb1735a00e"
 FULL_SNAPSHOT_ID = "4a9b608c9f01860a627237dd2409d1d50ec4b054"
@@ -138,11 +137,8 @@
         return [RawExtrinsicMetadataCore(m.format, m.metadata, m.discovery_date)]
 
 
-def test_load_artifact_metadata(swh_config, caplog):
-    storage = get_storage("memory")
-
-    loader = MetadataTestLoader(ORIGIN_URL)
-    loader.storage = storage
+def test_load_artifact_metadata(swh_storage, caplog):
+    loader = MetadataTestLoader(swh_storage, ORIGIN_URL)
 
     load_status = loader.load()
     assert load_status == {
@@ -154,7 +150,7 @@
         type=MetadataAuthorityType.REGISTRY, url="https://softwareheritage.org/",
     )
 
-    result = storage.raw_extrinsic_metadata_get(
+    result = swh_storage.raw_extrinsic_metadata_get(
         MetadataTargetType.DIRECTORY, DIRECTORY_SWHID, authority,
     )
     assert result.next_page_token is None
@@ -172,11 +168,8 @@
     )
 
 
-def test_load_metadata(swh_config, caplog):
-    storage = get_storage("memory")
-
-    loader = MetadataTestLoader(ORIGIN_URL)
-    loader.storage = storage
+def test_load_metadata(swh_storage, caplog):
+    loader = MetadataTestLoader(swh_storage, ORIGIN_URL)
 
     load_status = loader.load()
     assert load_status == {
@@ -184,13 +177,13 @@
         "snapshot_id": FULL_SNAPSHOT_ID,
     }
 
-    result = storage.raw_extrinsic_metadata_get(
+    result = swh_storage.raw_extrinsic_metadata_get(
         MetadataTargetType.DIRECTORY, DIRECTORY_SWHID, AUTHORITY,
     )
     assert result.next_page_token is None
     assert result.results == DIRECTORY_METADATA
 
-    result = storage.raw_extrinsic_metadata_get(
+    result = swh_storage.raw_extrinsic_metadata_get(
         MetadataTargetType.ORIGIN, ORIGIN_URL, AUTHORITY,
     )
     assert result.next_page_token is None
@@ -199,14 +192,8 @@
     assert caplog.text == ""
 
 
-def test_existing_authority(swh_config, caplog):
-    storage = get_storage("memory")
-
-    loader = MetadataTestLoader(ORIGIN_URL)
-    loader.storage = storage
-    loader.config["create_authorities"] = False
-
-    storage.metadata_authority_add([attr.evolve(AUTHORITY, metadata={})])
+def test_existing_authority(swh_storage, caplog):
+    loader = MetadataTestLoader(swh_storage, ORIGIN_URL)
 
     load_status = loader.load()
     assert load_status == {
@@ -214,7 +201,7 @@
         "snapshot_id": FULL_SNAPSHOT_ID,
     }
 
-    result = storage.raw_extrinsic_metadata_get(
+    result = swh_storage.raw_extrinsic_metadata_get(
         MetadataTargetType.DIRECTORY, DIRECTORY_SWHID, AUTHORITY,
     )
     assert result.next_page_token is None
@@ -223,14 +210,8 @@
     assert caplog.text == ""
 
 
-def test_existing_fetcher(swh_config, caplog):
-    storage = get_storage("memory")
-
-    loader = MetadataTestLoader(ORIGIN_URL)
-    loader.storage = storage
-    loader.config["create_fetchers"] = False
-
-    storage.metadata_fetcher_add([attr.evolve(FETCHER, metadata={})])
+def test_existing_fetcher(swh_storage, caplog):
+    loader = MetadataTestLoader(swh_storage, ORIGIN_URL)
 
     load_status = loader.load()
     assert load_status == {
@@ -238,7 +219,7 @@
         "snapshot_id": FULL_SNAPSHOT_ID,
     }
 
-    result = storage.raw_extrinsic_metadata_get(
+    result = swh_storage.raw_extrinsic_metadata_get(
         MetadataTargetType.DIRECTORY, DIRECTORY_SWHID, AUTHORITY,
     )
     assert result.next_page_token is None
diff --git a/swh/loader/pytest_plugin.py b/swh/loader/pytest_plugin.py
--- a/swh/loader/pytest_plugin.py
+++ b/swh/loader/pytest_plugin.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2019-2020  The Software Heritage developers
+# Copyright (C) 2019-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -11,30 +11,36 @@
 
 
 @pytest.fixture
-def swh_loader_config(swh_storage_postgresql) -> Dict[str, Any]:
+def swh_storage_backend_config(swh_storage_postgresql) -> Dict[str, Any]:
     return {
+        "cls": "retry",
         "storage": {
-            "cls": "pipeline",
-            "steps": [
-                {"cls": "retry"},
-                {"cls": "filter"},
-                {"cls": "buffer"},
-                {
+            "cls": "filter",
+            "storage": {
+                "cls": "buffer",
+                "storage": {
                     "cls": "local",
                     "db": swh_storage_postgresql.dsn,
                     "objstorage": {"cls": "memory"},
                 },
-            ],
+            },
         },
     }
 
 
 @pytest.fixture
-def swh_config(swh_loader_config, monkeypatch, tmp_path):
+def swh_loader_config(swh_storage_backend_config) -> Dict[str, Any]:
+    return {
+        "storage": swh_storage_backend_config,
+    }
+
+
+@pytest.fixture
+def swh_config(swh_loader_config, monkeypatch, tmp_path) -> str:
     conffile = os.path.join(str(tmp_path), "loader.yml")
     with open(conffile, "w") as f:
         f.write(yaml.dump(swh_loader_config))
-    monkeypatch.setenv("SWH_CONFIG_FILENAME", conffile)
+        monkeypatch.setenv("SWH_CONFIG_FILENAME", conffile)
     return conffile
 
 
diff --git a/swh/loader/tests/conftest.py b/swh/loader/tests/conftest.py
--- a/swh/loader/tests/conftest.py
+++ b/swh/loader/tests/conftest.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2019 The Software Heritage developers
+# Copyright (C) 2019-2021 The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -11,7 +11,7 @@
 @pytest.fixture
 def swh_loader_config() -> Dict[str, Any]:
     return {
-        "storage": {"cls": "pipeline", "steps": [{"cls": "memory",},],},
+        "storage": {"cls": "memory",},
         "deposit": {
             "url": "https://deposit.softwareheritage.org/1/private",
             "auth": {"username": "user", "password": "pass",},
diff --git a/swh/loader/tests/test_cli.py b/swh/loader/tests/test_cli.py
--- a/swh/loader/tests/test_cli.py
+++ b/swh/loader/tests/test_cli.py
@@ -1,15 +1,18 @@
-# Copyright (C) 2019-2020 The Software Heritage developers
+# Copyright (C) 2019-2021 The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import datetime
+import os
 
 from click.formatting import HelpFormatter
 from click.testing import CliRunner
 import pytest
+import yaml
 
-from swh.loader.cli import SUPPORTED_LOADERS, get_loader, list, run
+from swh.loader.cli import SUPPORTED_LOADERS, get_loader
+from swh.loader.cli import loader as loader_cli
 from swh.loader.package.loader import PackageLoader
 
 
@@ -23,18 +26,18 @@
         get_loader(loader_type, url="db-url")
 
 
-def test_get_loader(swh_config):
+def test_get_loader(swh_loader_config):
     """Instantiating a supported loader should be ok
 
     """
     loader_input = {
-        "archive": {"url": "some-url", "artifacts": [],},
+        "archive": {"url": "some-url", "artifacts": []},
         "debian": {"url": "some-url", "date": "something", "packages": [],},
-        "deposit": {"url": "some-url", "deposit_id": 1,},
         "npm": {"url": "https://www.npmjs.com/package/onepackage",},
         "pypi": {"url": "some-url",},
     }
     for loader_type, kwargs in loader_input.items():
+        kwargs["storage"] = swh_loader_config["storage"]
         loader = get_loader(loader_type, **kwargs)
         assert isinstance(loader, PackageLoader)
 
@@ -50,31 +53,44 @@
 
     """
     runner = CliRunner()
-    result = runner.invoke(run, ["-h"])
+
+    result = runner.invoke(loader_cli, ["run", "-h"])
 
     assert result.exit_code == 0
     usage_prefix = _write_usage(
-        "run", f"[OPTIONS] [{'|'.join(SUPPORTED_LOADERS)}] URL [OPTIONS]..."
+        "loader", f"run [OPTIONS] [{'|'.join(SUPPORTED_LOADERS)}]\n"
     )
-    expected_help_msg = f"""{usage_prefix}
+    assert result.output.startswith(usage_prefix)
 
-  Ingest with loader <type> the origin located at <url>
 
-Options:
-  -h, --help  Show this message and exit.
-"""
-    assert result.output.startswith(expected_help_msg)
+def test_run_with_configuration_failure(tmp_path):
+    """Triggering a load should fail since configuration is incomplete
+
+    """
+    runner = CliRunner()
+
+    conf_path = os.path.join(str(tmp_path), "cli.yml")
+    with open(conf_path, "w") as f:
+        f.write(yaml.dump({}))
+
+    with pytest.raises(ValueError, match="Missing storage"):
+        runner.invoke(
+            loader_cli, ["-C", conf_path, "run", "pypi", "url=https://some-url",],
+            catch_exceptions=False
+        )
 
 
 def test_run_pypi(mocker, swh_config):
     """Triggering a load should be ok
 
     """
-    mock_loader = mocker.patch("swh.loader.package.pypi.loader.PyPILoader")
+    mock_loader = mocker.patch("swh.loader.package.pypi.loader.PyPILoader.load")
     runner = CliRunner()
-    result = runner.invoke(run, ["pypi", "https://some-url"])
+    result = runner.invoke(
+        loader_cli, ["-C", swh_config, "run", "pypi", "url=https://some-url",]
+    )
     assert result.exit_code == 0
-    mock_loader.assert_called_once_with(url="https://some-url")  # constructor
+    mock_loader.assert_called_once_with()
 
 
 def test_run_with_visit_date(mocker, swh_config):
@@ -86,14 +102,17 @@
     runner = CliRunner()
     input_date = "2016-05-03 15:16:32+00"
     result = runner.invoke(
-        run, ["npm", "https://some-url", f"visit_date='{input_date}'"]
+        loader_cli, ["run", "npm", "https://some-url", f"visit_date='{input_date}'"]
     )
     assert result.exit_code == 0
     expected_parsed_date = datetime.datetime(
         2016, 5, 3, 15, 16, 32, tzinfo=datetime.timezone.utc
     )
     mock_loader.assert_called_once_with(
-        "npm", url="https://some-url", visit_date=expected_parsed_date
+        "npm",
+        storage={"cls": "memory"},
+        url="https://some-url",
+        visit_date=expected_parsed_date,
     )
 
 
@@ -102,12 +121,11 @@
 
     """
     runner = CliRunner()
-    result = runner.invoke(list, ["--help"])
+    result = runner.invoke(loader_cli, ["list", "--help"])
     assert result.exit_code == 0
-    usage_prefix = _write_usage(
-        "list", f"[OPTIONS] [[{'|'.join(['all'] + SUPPORTED_LOADERS)}]]"
-    )
+    usage_prefix = _write_usage("loader", "list [OPTIONS]\n")
     expected_help_msg = f"""{usage_prefix}
+                   [[{'|'.join(['all'] + SUPPORTED_LOADERS)}]]
 
   List supported loaders and optionally their arguments
 
@@ -122,10 +140,9 @@
 
     """
     runner = CliRunner()
-    result = runner.invoke(list, ["npm"])
+    result = runner.invoke(loader_cli, ["list", "npm"])
     assert result.exit_code == 0
     expected_help_msg = """
 Loader: Load npm origin's artifact releases into swh archive.
-signature: (url: str)
 """
     assert result.output.startswith(expected_help_msg[1:])
diff --git a/swh/loader/tests/test_init.py b/swh/loader/tests/test_init.py
--- a/swh/loader/tests/test_init.py
+++ b/swh/loader/tests/test_init.py
@@ -1,4 +1,4 @@
-# Copyright (C) 2020  The Software Heritage developers
+# Copyright (C) 2020-2021  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -163,6 +163,15 @@
 )
 
 
+@pytest.fixture
+def swh_storage_backend_config(swh_storage_postgresql):
+    return {
+        "cls": "local",
+        "db": swh_storage_postgresql.dsn,
+        "objstorage": {"cls": "memory"},
+    }
+
+
 @pytest.fixture
 def mock_storage(mocker):
     mock_storage = mocker.patch("swh.loader.tests.origin_get_latest_visit_status")