Closes Issue 21262: New method assert_not_called for Mock.

It raises AssertionError if the mock has been called.

1 files changed, 8 insertions, 0 deletions

diff --git a/Lib/unittest/mock.py b/Lib/unittest/mock.py
index 48e7dd078f2..6c00bc66f8f 100644
--- a/Lib/unittest/mock.py
+++ b/Lib/unittest/mock.py
@@ -758,6 +758,14 @@ class NonCallableMock(Base):
         else:
             return _call
 
+    def assert_not_called(_mock_self, *args, **kwargs):
+        """assert that the mock was never called.
+        """
+        self = _mock_self
+        if self.call_count != 0:
+            msg = ("Expected '%s' to not have been called. Called %s times." %
+                   (self._mock_name or 'mock', self.call_count))
+            raise AssertionError(msg)
 
     def assert_called_with(_mock_self, *args, **kwargs):
         """assert that the mock was called with the specified arguments.