diff --git a/modoboa/admin/tests/test_account.py b/modoboa/admin/tests/test_account.py
index ea3080ad4..e44914df6 100644
--- a/modoboa/admin/tests/test_account.py
+++ b/modoboa/admin/tests/test_account.py
@@ -6,7 +6,7 @@ from django.core.urlresolvers import reverse
 from django.test import override_settings
 
 from modoboa.core import factories as core_factories
-from modoboa.core import tests as core_tests
+from modoboa.core.tests import test_core
 from modoboa.core.models import User
 from modoboa.lib import parameters
 from modoboa.lib.tests import ModoTestCase
@@ -221,7 +221,7 @@ class AccountTestCase(ModoTestCase):
     'modoboa.lib.authbackends.LDAPBackend',
     'modoboa.lib.authbackends.SimpleBackend',
 ))
-class LDAPAccountTestCase(core_tests.LDAPTestCaseMixin, ModoTestCase):
+class LDAPAccountTestCase(test_core.LDAPTestCaseMixin, ModoTestCase):
     """Check LDAP related code."""
 
     def test_autocreate_disabled(self):
diff --git a/modoboa/core/extensions.py b/modoboa/core/extensions.py
index 6c29b2b27..78e8f36d1 100644
--- a/modoboa/core/extensions.py
+++ b/modoboa/core/extensions.py
@@ -5,7 +5,6 @@ from django.conf.urls import include
 
 
 class ModoExtension(object):
-
     """
     Base extension class.
 
@@ -23,22 +22,23 @@ class ModoExtension(object):
     available_for_topredirection = False
 
     def infos(self):
-        return dict(
-            name=self.name, label=self.label, version=self.version,
-            description=self.description, url=self.url,
-            always_active=self.always_active
-        )
+        """Information about this extension."""
+        return {
+            "name": self.name, "label": self.label, "version": self.version,
+            "description": self.description, "url": self.url,
+            "always_active": self.always_active
+        }
 
     def load_initial_data(self):
         """Declare extension data in this method."""
         pass
 
     def load(self):
+        """Add extension loading tasks in this method."""
         pass
 
 
 class ExtensionsPool(object):
-
     """The extensions manager"""
 
     def __init__(self):
@@ -60,11 +60,8 @@ class ExtensionsPool(object):
             self.extensions[name]["instance"] = self.extensions[name]["cls"]()
         return self.extensions[name]["instance"]
 
-    def is_extension_installed(self, name):
-        """Check if an extension is installed ir not."""
-        return name in settings.MODOBOA_APPS
-
     def get_extension_infos(self, name):
+        """Return information about the specified extension."""
         instance = self.get_extension(name)
         if instance is None:
             return None
diff --git a/modoboa/core/tests/__init__.py b/modoboa/core/tests/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/modoboa/core/tests/stupid_extension_1/__init__.py b/modoboa/core/tests/stupid_extension_1/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/modoboa/core/tests/stupid_extension_1/modo_extension.py b/modoboa/core/tests/stupid_extension_1/modo_extension.py
new file mode 100644
index 000000000..4cc7f4121
--- /dev/null
+++ b/modoboa/core/tests/stupid_extension_1/modo_extension.py
@@ -0,0 +1,20 @@
+"""A stupid extension used for tests."""
+
+from modoboa.core import extensions
+
+
+class StupidExtension1(extensions.ModoExtension):
+    """Stupid extension to use with tests."""
+
+    name = "stupid_extension_1"
+    label = "Stupid extension"
+    version = "1.0.0"
+    description = "A stupid extension"
+
+    def load(self):
+        pass
+
+    def load_initial_data(self):
+        raise RuntimeError
+
+extensions.exts_pool.register_extension(StupidExtension1)
diff --git a/modoboa/core/tests/stupid_extension_2/__init__.py b/modoboa/core/tests/stupid_extension_2/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/modoboa/core/tests/stupid_extension_2/modo_extension.py b/modoboa/core/tests/stupid_extension_2/modo_extension.py
new file mode 100644
index 000000000..47824e924
--- /dev/null
+++ b/modoboa/core/tests/stupid_extension_2/modo_extension.py
@@ -0,0 +1,14 @@
+"""A stupid extension used for tests."""
+
+from modoboa.core import extensions
+
+
+class StupidExtension2(extensions.ModoExtension):
+    """Stupid extension to use with tests."""
+
+    name = "stupid_extension_2"
+    label = "Stupid extension"
+    version = "1.0.0"
+    description = "A stupid extension"
+
+extensions.exts_pool.register_extension(StupidExtension2, show=False)
diff --git a/modoboa/core/tests/stupid_extension_2/urls.py b/modoboa/core/tests/stupid_extension_2/urls.py
new file mode 100644
index 000000000..552d09822
--- /dev/null
+++ b/modoboa/core/tests/stupid_extension_2/urls.py
@@ -0,0 +1,3 @@
+"""Custom urls."""
+
+urlpatterns = []
diff --git a/modoboa/core/tests.py b/modoboa/core/tests/test_core.py
similarity index 99%
rename from modoboa/core/tests.py
rename to modoboa/core/tests/test_core.py
index de7774d91..598124fd9 100644
--- a/modoboa/core/tests.py
+++ b/modoboa/core/tests/test_core.py
@@ -13,9 +13,9 @@ from modoboa.lib import parameters
 from modoboa.lib.tests import ModoTestCase
 from modoboa.lib.tests import NO_LDAP
 
-from . import factories
-from . import mocks
-from . import models
+from .. import factories
+from .. import mocks
+from .. import models
 
 
 class AuthenticationTestCase(ModoTestCase):
diff --git a/modoboa/core/tests/test_extensions.py b/modoboa/core/tests/test_extensions.py
new file mode 100644
index 000000000..b99c1502c
--- /dev/null
+++ b/modoboa/core/tests/test_extensions.py
@@ -0,0 +1,73 @@
+"""Extensions management related test cases."""
+
+import os
+import sys
+
+from testfixtures import compare
+
+from django.core import management
+from django.test import TestCase, override_settings
+
+from .. import extensions
+
+sys.path.append(os.path.dirname(__file__))
+
+CUSTOM_APPS = (
+    "modoboa",
+    "modoboa.core",
+    "modoboa.lib",
+    "modoboa.admin",
+    "modoboa.limits",
+    "modoboa.relaydomains",
+    "stupid_extension_1",
+    "stupid_extension_2",
+)
+
+
+class ExtensionTestCase(TestCase):
+    """Extensions related tests."""
+
+    @classmethod
+    def setUpClass(cls):
+        """Initiate test context."""
+        cls.pool = extensions.exts_pool
+        with override_settings(MODOBOA_APPS=CUSTOM_APPS):
+            cls.pool.load_all()
+
+    @classmethod
+    def tearDownClass(cls):
+        """Reset context."""
+        del cls.pool.extensions["stupid_extension_1"]
+        del cls.pool.extensions["stupid_extension_2"]
+
+    def test_register(self):
+        """Test if registering works."""
+        self.assertIn("stupid_extension_1", self.pool.extensions)
+
+    def test_get_extension(self):
+        """Check getter method."""
+        self.assertIsNone(self.pool.get_extension("toto"))
+        instance = self.pool.get_extension("stupid_extension_1")
+        self.assertEqual(instance.__class__.__name__, "StupidExtension1")
+
+    def test_get_extension_infos(self):
+        """Check getter method."""
+        self.assertIsNone(self.pool.get_extension_infos("toto"))
+        infos = self.pool.get_extension_infos("stupid_extension_1")
+        compare(infos, {
+            "name": "stupid_extension_1", "label": "Stupid extension",
+            "version": "1.0.0", "description": "A stupid extension",
+            "url": None, "always_active": False
+        })
+
+    def test_list_all(self):
+        """Check list_all method."""
+        result = self.pool.list_all()
+        self.assertEqual(len(result), 1)
+        ext = result[0]
+        self.assertEqual(ext["id"], "stupid_extension_1")
+
+    def test_load_initial_data(self):
+        """Check if method is called."""
+        with self.assertRaises(RuntimeError):
+            management.call_command("load_initial_data")