diff --git a/swh/storage/api/server.py b/swh/storage/api/server.py
--- a/swh/storage/api/server.py
+++ b/swh/storage/api/server.py
@@ -5,7 +5,7 @@
 
 import logging
 import os
-from typing import Any, Dict
+from typing import Any, Dict, Optional
 
 from swh.core import config
 from swh.core.api import RPCServerApp
@@ -79,7 +79,7 @@
 api_cfg = None
 
 
-def load_and_check_config(config_path: str) -> Dict[str, Any]:
+def load_and_check_config(config_path: Optional[str]) -> Dict[str, Any]:
     """Check the minimal configuration is set to run the api or raise an
        error explanation.
 
@@ -106,7 +106,7 @@
     return cfg
 
 
-def make_app_from_configfile():
+def make_app_from_configfile() -> StorageServerApp:
     """Run the WSGI app from the webserver, loading the configuration from
        a configuration file.
 
diff --git a/swh/storage/tests/test_server.py b/swh/storage/tests/test_server.py
--- a/swh/storage/tests/test_server.py
+++ b/swh/storage/tests/test_server.py
@@ -3,10 +3,18 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
+import os
+from typing import Any, Dict
+
 import pytest
 import yaml
 
-from swh.storage.api.server import load_and_check_config
+from swh.core.config import load_from_envvar
+from swh.storage.api.server import (
+    StorageServerApp,
+    load_and_check_config,
+    make_app_from_configfile,
+)
 
 
 def prepare_config_file(tmpdir, content, name="config.yml"):
@@ -58,3 +66,31 @@
     config_path = prepare_config_file(tmpdir, config)
     cfg = load_and_check_config(config_path)
     assert cfg == config
+
+
+@pytest.fixture
+def swh_storage_server_config(
+    swh_storage_backend_config: Dict[str, Any]
+) -> Dict[str, Any]:
+    return {"storage": swh_storage_backend_config}
+
+
+@pytest.fixture
+def swh_storage_config(monkeypatch, swh_storage_server_config, tmp_path):
+    conf_path = os.path.join(str(tmp_path), "storage.yml")
+    with open(conf_path, "w") as f:
+        f.write(yaml.dump(swh_storage_server_config))
+    monkeypatch.setenv("SWH_CONFIG_FILENAME", conf_path)
+    return conf_path
+
+
+def test_server_make_app_from_config_file(swh_storage_config):
+    app = make_app_from_configfile()
+    expected_cfg = load_from_envvar()
+
+    assert app is not None
+    assert isinstance(app, StorageServerApp)
+    assert app.config["storage"] == expected_cfg["storage"]
+
+    app2 = make_app_from_configfile()
+    assert app is app2