diff --git a/swh/indexer/tests/test_language.py b/swh/indexer/tests/test_language.py
new file mode 100644
--- /dev/null
+++ b/swh/indexer/tests/test_language.py
@@ -0,0 +1,112 @@
+# Copyright (C) 2015-2017  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 unittest
+import logging
+from nose.tools import istest
+from swh.indexer import language
+from swh.indexer.language import ContentLanguageIndexer
+from swh.indexer.tests.test_utils import MockObjStorage
+
+
+class MockStorage():
+    """Mock storage to simplify reading indexers' outputs.
+    """
+    def content_language_add(self, languages, conflict_update=None):
+        self.state = languages
+        self.conflict_update = conflict_update
+
+    def indexer_configuration_get(self, tool):
+        return {
+            'id': 20,
+        }
+
+
+class TestLanguageIndexer(ContentLanguageIndexer):
+    """Specific language whose configuration is enough to satisfy the
+       indexing tests.
+    """
+    def prepare(self):
+        self.config = {
+            'destination_queue': None,
+            'rescheduling_task': None,
+            'tools':  {
+                'name': 'pygments',
+                'version': '2.0.1+dfsg-1.1+deb8u1',
+                'configuration': {
+                    'type': 'library',
+                    'debian-package': 'python3-pygments',
+                    'max_content_size': 10240,
+                },
+            }
+        }
+        self.storage = MockStorage()
+        self.log = logging.getLogger('swh.indexer')
+        self.objstorage = MockObjStorage()
+        self.task_destination = None
+        self.rescheduling_task = self.config['rescheduling_task']
+        self.tool_config = self.config['tools']['configuration']
+        self.max_content_size = self.tool_config['max_content_size']
+        self.tools = self.retrieve_tools_information()
+
+
+class Language(unittest.TestCase):
+    """
+    Tests pygments tool for language detection
+    """
+    def setUp(self):
+        self.maxDiff = None
+
+    @istest
+    def test_compute_language_none(self):
+        # given
+        self.content = ""
+        self.declared_language = {
+            'lang': None
+        }
+        # when
+        result = language.compute_language(self.content)
+        # then
+        self.assertEqual(self.declared_language, result)
+
+    @istest
+    def test_index_content_language_python(self):
+        # given
+        # testing python
+        sha1s = ['02fb2c89e14f7fab46701478c83779c7beb7b069']
+        lang_indexer = TestLanguageIndexer()
+
+        # when
+        lang_indexer.run(sha1s, policy_update='ignore-dups')
+        results = lang_indexer.storage.state
+
+        expected_results = [{
+            'id': '02fb2c89e14f7fab46701478c83779c7beb7b069',
+            'indexer_configuration_id': 20,
+            'lang': 'python'
+        }]
+        # then
+        self.assertEqual(expected_results, results)
+
+    @istest
+    def test_index_content_language_c(self):
+        # given
+        # testing c
+        sha1s = ['103bc087db1d26afc3a0283f38663d081e9b01e6']
+        lang_indexer = TestLanguageIndexer()
+
+        # when
+        lang_indexer.run(sha1s, policy_update='ignore-dups')
+        results = lang_indexer.storage.state
+
+        expected_results = [{
+            'id': '103bc087db1d26afc3a0283f38663d081e9b01e6',
+            'indexer_configuration_id': 20,
+            'lang': 'c'
+        }]
+
+        # then
+        self.assertEqual('c', results[0]['lang'])
+        self.assertEqual(expected_results, results)
diff --git a/swh/indexer/tests/test_mimetype.py b/swh/indexer/tests/test_mimetype.py
--- a/swh/indexer/tests/test_mimetype.py
+++ b/swh/indexer/tests/test_mimetype.py
@@ -8,7 +8,8 @@
 from nose.tools import istest
 
 from swh.indexer.mimetype import ContentMimetypeIndexer
-from swh.objstorage.exc import ObjNotFoundError
+
+from swh.indexer.tests.test_utils import MockObjStorage
 
 
 class MockStorage():
@@ -25,29 +26,6 @@
         }
 
 
-class MockStorageWrongConfiguration():
-    def indexer_configuration_get(self, tool):
-        return None
-
-
-class MockObjStorage():
-    """Mock objstorage with predefined contents.
-
-    """
-    def __init__(self):
-        self.data = {
-            '01c9379dfc33803963d07c1ccc748d3fe4c96bb50': b'this is some text',
-            '688a5ef812c53907562fe379d4b3851e69c7cb15': b'another text',
-            '8986af901dd2043044ce8f0d8fc039153641cf17': b'yet another text',
-        }
-
-    def get(self, sha1):
-        raw_content = self.data.get(sha1)
-        if not raw_content:
-            raise ObjNotFoundError()
-        return raw_content
-
-
 class TestMimetypeIndexer(ContentMimetypeIndexer):
     """Specific mimetype whose configuration is enough to satisfy the
        indexing tests.
diff --git a/swh/indexer/tests/test_utils.py b/swh/indexer/tests/test_utils.py
new file mode 100644
--- /dev/null
+++ b/swh/indexer/tests/test_utils.py
@@ -0,0 +1,62 @@
+
+# Copyright (C) 2017  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
+
+from swh.objstorage.exc import ObjNotFoundError
+
+
+class MockStorageWrongConfiguration():
+    def indexer_configuration_get(self, tool):
+        return None
+
+
+class MockObjStorage():
+    """Mock objstorage with predefined contents.
+
+    """
+    def __init__(self):
+        self.data = {
+            '01c9379dfc33803963d07c1ccc748d3fe4c96bb50': b'this is some text',
+            '688a5ef812c53907562fe379d4b3851e69c7cb15': b'another text',
+            '8986af901dd2043044ce8f0d8fc039153641cf17': b'yet another text',
+            '02fb2c89e14f7fab46701478c83779c7beb7b069': b"""
+            import unittest
+            import logging
+            from nose.tools import istest
+            from swh.indexer.mimetype import ContentMimetypeIndexer
+            from swh.indexer.tests.test_utils import MockObjStorage
+
+            class MockStorage():
+                def content_mimetype_add(self, mimetypes):
+                    self.state = mimetypes
+                    self.conflict_update = conflict_update
+
+                def indexer_configuration_get(self, tool):
+                    return {
+                        'id': 10,
+                    }
+            """,
+            '103bc087db1d26afc3a0283f38663d081e9b01e6': b"""
+                #ifndef __AVL__
+                #define __AVL__
+
+                typedef struct _avl_tree avl_tree;
+
+                typedef struct _data_t {
+                  int content;
+                } data_t;
+            """,
+            '93666f74f1cf635c8c8ac118879da6ec5623c410': b"""
+            (should 'pygments (recognize 'lisp 'easily))
+
+            """
+
+        }
+
+    def get(self, sha1):
+        raw_content = self.data.get(sha1)
+        if not raw_content:
+            raise ObjNotFoundError()
+        return raw_content