Add a hacking rule for assert_has_calls

Add the following hacking rule.

* N366: The assert_has_calls is a method rather than a variable.

  Not correct: mock_method.assert_has_calls = [mock.call(0)]
  Correct:     mock_method.assert_has_calls([mock.call(0)])

This patch is a follow-up patch for
Id094dd90efde09b9a835d4492f4a92b8f8ad296e.

Change-Id: I892f8c23ee44f2b3518776a9705e3543f3115cae
Signed-off-by: Takashi Natsume <takanattie@gmail.com>

HACKING.rst

@@ -67,6 +67,7 @@ Nova Specific Commandments
 - [N363] Disallow ``(not_a_tuple)`` because you meant ``(a_tuple_of_one,)``.
 - [N364] Check non-existent mock assertion methods and attributes.
 - [N365] Check misuse of assertTrue/assertIsNone.
+- [N366] The assert_has_calls is a method rather than a variable.
 
 Creating Unit Tests
 -------------------

nova/hacking/checks.py

@@ -127,6 +127,8 @@ mock_attribute_re = re.compile(r"[\.\(](retrun_value)[,=\s]")
 # Regex for useless assertions
 useless_assertion_re = re.compile(
     r"\.((assertIsNone)\(None|(assertTrue)\((True|\d+|'.+'|\".+\")),")
+# Regex for misuse of assert_has_calls
+mock_assert_has_calls_re = re.compile(r"\.assert_has_calls\s?=")
 
 
 class BaseASTChecker(ast.NodeVisitor):
@@ -922,3 +924,18 @@ def useless_assertion(logical_line, filename):
         match = useless_assertion_re.search(logical_line)
         if match:
             yield (0, msg % (match.group(2) or match.group(3)))
+
+
+@core.flake8ext
+def check_assert_has_calls(logical_line, filename):
+    """Check misuse of assert_has_calls.
+
+    Not correct: mock_method.assert_has_calls = [mock.call(0)]
+    Correct:     mock_method.assert_has_calls([mock.call(0)])
+
+    N366
+    """
+    msg = "N366: The assert_has_calls is a method rather than a variable."
+    if ('nova/tests/' in filename and
+            mock_assert_has_calls_re.search(logical_line)):
+        yield (0, msg)

nova/tests/unit/test_hacking.py

@@ -909,3 +909,27 @@ class HackingTestCase(test.NoDBTestCase):
         self._assert_has_no_errors(
             code, checks.useless_assertion,
             filename="nova/tests/unit/test_context.py")
+
+    def test_check_assert_has_calls(self):
+        code = """
+                   mock_method.assert_has_calls = [mock.call(1)]
+                   mock_method2.assert_has_calls = [
+                       mock.call(1), mock.call(2)]
+               """
+        errors = [(x + 1, 0, 'N366') for x in range(2)]
+        # Check errors in 'nova/tests' directory.
+        self._assert_has_errors(
+            code, checks.check_assert_has_calls,
+            expected_errors=errors, filename="nova/tests/unit/test_context.py")
+        # Check no errors in other than 'nova/tests' directory.
+        self._assert_has_no_errors(
+            code, checks.check_assert_has_calls,
+            filename="nova/compute/api.py")
+        code = """
+                   mock_method.assert_has_calls([mock.call(1)])
+                   mock_method2.assert_has_calls([
+                       mock.call(1), mock.call(2)])
+               """
+        self._assert_has_no_errors(
+            code, checks.check_assert_has_calls,
+            filename="nova/tests/unit/test_context.py")

tox.ini

@@ -314,6 +314,7 @@ extension =
   N363 = checks:did_you_mean_tuple
   N364 = checks:nonexistent_assertion_methods_and_attributes
   N365 = checks:useless_assertion
+  N366 = checks:check_assert_has_calls
 paths =
   ./nova/hacking