Replace assertEqual(None, *) with assertIsNone in tests

Replace assertEqual(None, *) with assertIsNone in tests to
have more clear messages in case of failure.

Change-Id: Ice018dfd3e48326ce9cac58342d03979559b9e82

HACKING.rst

@@ -32,6 +32,7 @@ Neutron Specific Commandments
 - [N343] Production code must not import from neutron.tests.*
 - [N344] Python 3: Do not use filter(lambda obj: test(obj), data). Replace it
   with [obj for obj in data if test(obj)].
+- [N345] Detect wrong usage with assertEqual(None, A) and assertEqual(A, None).
 
 Creating Unit Tests
 -------------------

neutron/hacking/checks.py

@@ -414,6 +414,19 @@ def check_python3_no_filter(logical_line):
         yield(0, msg)
 
 
+@flake8ext
+def check_assertIsNone(logical_line, filename):
+    """N345 - Enforce using assertIsNone."""
+    if 'neutron/tests/' in filename:
+        asse_eq_end_with_none_re = re.compile(r"assertEqual\(.*?,\s+None\)$")
+        asse_eq_start_with_none_re = re.compile(r"assertEqual\(None,")
+        res = (asse_eq_start_with_none_re.search(logical_line) or
+               asse_eq_end_with_none_re.search(logical_line))
+        if res:
+            yield (0, "N345: assertEqual(A, None) or assertEqual(None, A) "
+                   "sentences not allowed")
+
+
 def factory(register):
     register(validate_log_translations)
     register(use_jsonutils)
@@ -435,3 +448,4 @@ def factory(register):
     register(check_delayed_string_interpolation)
     register(check_no_imports_from_tests)
     register(check_python3_no_filter)
+    register(check_assertIsNone)

neutron/tests/tempest/api/test_floating_ips.py

@@ -100,4 +100,4 @@ class FloatingIPTestJSON(base.BaseNetworkTest):
         # disassociate
         body = self.client.update_floatingip(body['floatingip']['id'],
                                              port_id=None)
-        self.assertEqual(None, body['floatingip']['port_id'])
+        self.assertIsNone(body['floatingip']['port_id'])

neutron/tests/unit/db/test_l3_hamode_db.py

@@ -756,8 +756,7 @@ class L3HATestCase(L3HATestFramework):
 
     def test_get_active_host_for_ha_router(self):
         router = self._create_router()
-        self.assertEqual(
-            None,
+        self.assertIsNone(
             self.plugin.get_active_host_for_ha_router(
                 self.admin_ctx, router['id']))
         self.plugin.update_routers_states(

neutron/tests/unit/hacking/test_checks.py

@@ -360,6 +360,16 @@ class HackingTestCase(base.BaseTestCase):
         self.assertLinePasses(f, "filter(function, range(0,10))")
         self.assertLinePasses(f, "lambda x, y: x+y")
 
+    def test_check_assertIsNone(self):
+        self.assertEqual(1, len(list(checks.check_assertIsNone(
+            "self.assertEqual(A, None)", "neutron/tests/test_assert.py"))))
+
+        self.assertEqual(1, len(list(checks.check_assertIsNone(
+            "self.assertEqual(None, A)", "neutron/tests/test_assert.py"))))
+
+        self.assertEqual(0, len(list(checks.check_assertIsNone(
+            "self.assertIsNone()", "neutron/tests/test_assert.py"))))
+
 
 # The following is borrowed from hacking/tests/test_doctest.py.
 # Tests defined in docstring is easier to understand