diff --git a/vlorentz/get_gemspec_examples.py b/vlorentz/get_gemspec_examples.py
deleted file mode 100644
index 699931f..0000000
--- a/vlorentz/get_gemspec_examples.py
+++ /dev/null
@@ -1,60 +0,0 @@
-import csv
-import os
-import os.path
-import subprocess
-
-from swh.model.hashutil import hash_to_bytes
-from swh.objstorage.api.client import RemoteObjStorage
-from swh.objstorage.exc import ObjNotFoundError
-
-BASE_DIR = os.path.expanduser('~/datasets/')
-
-GEMSPEC_LIST_QUERY = """
-select encode(name, 'escape'), encode(sha1, 'hex')
-from directory_entry_file
-inner join content on (sha1_git = target)
-where encode(name, 'escape') like '%.gemspec'
-order by id desc
-limit 100;"""
-GEMSPECS_DIR = os.path.join(BASE_DIR, 'gemspecs')
-GEMSPEC_LIST_PATH = os.path.join(BASE_DIR, 'gemspec_list.csv')
-
-objstorage_client = RemoteObjStorage(
-    url='http://uffizi.internal.softwareheritage.org:5003/')
-
-def get_gemspec_list():
-    if os.path.isfile(GEMSPEC_LIST_PATH):
-        print('Using cached gemspec list')
-        return
-    else:
-        print('Getting gemspec list')
-        csv = subprocess.check_output([
-            'psql', 'service=swh-replica', '-c', GEMSPEC_LIST_QUERY,
-            '-t', '-A', '-F,'])
-        print('Done')
-        with open(GEMSPEC_LIST_PATH, 'wb') as fd:
-            fd.write(csv)
-
-def download_gemspecs():
-    with open(GEMSPEC_LIST_PATH) as fd:
-        for (name, sha1) in csv.reader(fd):
-            download_gemspec(name, sha1)
-
-def download_gemspec(name, sha1):
-    path = os.path.join(GEMSPECS_DIR, '{}_{}'.format(name, sha1))
-    if os.path.isfile(path):
-        print('{} {}:\tskipped (already have it)'.format(name, sha1))
-        return
-    try:
-        obj = objstorage_client.get(sha1)
-    except ObjNotFoundError:
-        print('{} {}:\tnot in objstorage'.format(sha1, name))
-        return
-    else:
-        print('{} {}:\tdownloaded'.format(sha1, name))
-    with open(path, 'wb') as fd:
-        fd.write(obj)
-
-os.makedirs(GEMSPECS_DIR, exist_ok=True)
-get_gemspec_list()
-download_gemspecs()
diff --git a/vlorentz/run_afl.txt b/vlorentz/run_afl.txt
new file mode 100644
index 0000000..4c98166
--- /dev/null
+++ b/vlorentz/run_afl.txt
@@ -0,0 +1,3 @@
+py-afl-fuzz -t 2000 -m 200 -i ~/datasets/gemspec -o fuzzing-results -- python3 ~/swh-environment/snippets/vlorentz/run_mapping.py GemspecMapper @@
+
+py-afl-fuzz -t 2000 -m 200 -i ~/datasets/pkginfo -o fuzzing-results -- python3 ~/swh-environment/snippets/vlorentz/run_mapping.py GemspecMapper @@
diff --git a/vlorentz/run_mapping.py b/vlorentz/run_mapping.py
new file mode 100644
index 0000000..cfff06c
--- /dev/null
+++ b/vlorentz/run_mapping.py
@@ -0,0 +1,42 @@
+import os
+import os.path
+import pprint
+import sys
+import traceback
+
+import afl
+
+#afl.init()
+
+from swh.indexer.metadata_dictionary import MAPPINGS
+
+try:
+    mapping_name = sys.argv[1]
+    file_name = sys.argv[2]
+except KeyError:
+    print('Syntax: ./run_mapping.py {GemspecMapping,NpmMapping,...}')
+    exit(1)
+
+#afl.init()
+while afl.loop(1000):
+#if True:
+    #sys.stdin.buffer.seek(0)
+    #file_content = sys.stdin.buffer.read()
+    with open(file_name, 'rb') as fd:
+        file_content = fd.read()
+    """
+    with open('/tmp/data', 'ab') as fd:
+        fd.write(repr(file_content).encode() + b'\n')
+        fd.write(repr(sys.argv).encode() + b'\n')"""
+    assert b'abcd' not in file_content
+    try:
+        MAPPINGS[mapping_name].translate(file_content)
+    except:
+        with open('/tmp/tb.txt', 'a') as fd:
+            fd.write('tb:\n')
+            fd.write(repr(list(MAPPINGS)) + '\n')
+            fd.write(traceback.format_exc())
+            fd.flush()
+        raise
+
+os._exit(0)