add assert_not_is_instance()

Author: srittau

NEWS.rst

@@ -3,6 +3,7 @@ Version 0.6
 
 * add assert_less(), assert_less_equal(), assert_greater(), and
   assert_greater_equal()
+* add assert_not_is_instance()
 * assert_datetime_about_now()/assert_datetime_about_now_utc(): Handle
   comparison with None more gracefully.
 

asserts.py

@@ -346,13 +346,28 @@ def assert_is_instance(obj, cls, msg=None):
     >>> assert_is_instance(5, str)
     Traceback (most recent call last):
         ...
-    AssertionError: 5 is of <class 'int'>, expected <class 'str'>
+    AssertionError: 5 is an instance of <class 'int'>, expected <class 'str'>
 
     """
     if not isinstance(obj, cls):
-        msg = (msg if msg is not None else
-               repr(obj) + " is of " + repr(obj.__class__) +
-               ", expected " + repr(cls))
+        msg = (msg or "{!r} is an instance of {!r}, expected {!r}".format(
+            obj, obj.__class__, cls))
+        fail(msg)
+
+
+def assert_not_is_instance(obj, cls, msg=None):
+    """Fail if an object is an instance of a class or tuple of classes.
+
+    >>> assert_not_is_instance(5, str)
+    >>> assert_not_is_instance(5, (str, bytes))
+    >>> assert_not_is_instance('foo', str)
+    Traceback (most recent call last):
+        ...
+    AssertionError: 'foo' is an instance of <class 'str'>
+
+    """
+    if isinstance(obj, cls):
+        msg = msg or "{!r} is an instance of {!r}".format(obj, obj.__class__)
         fail(msg)
 
 

test_asserts.py

@@ -25,6 +25,7 @@
     assert_not_in,
     assert_regex,
     assert_is_instance,
+    assert_not_is_instance,
     assert_has_attr,
     assert_datetime_about_now,
     assert_datetime_about_now_utc,
@@ -341,26 +342,36 @@ def test_assert_between__too_high__custom_message(self):
         with _assert_raises_assertion("my message"):
             assert_between(0, 10, 11, msg="my message")
 
-    def test_assert_is_instance__is_instance(self):
+    def test_assert_is_instance(self):
         assert_is_instance(4, int)
-
-    def test_assert_is_instance__is_instance__multiple_classes(self):
         assert_is_instance(4, (str, int))
-
-    def test_assert_is_instance__is_sub_class(self):
         assert_is_instance(OSError(), Exception)
+        with _assert_raises_assertion("my message"):
+            assert_is_instance("my string", int, msg="my message")
 
-    def test_assert_is_instance__not_instance__default_message(self):
-        expected_message = ("'my string' is of <class 'str'>, "
-                            "expected <class 'int'>")
+    def test_assert_is_instance__default_message(self):
+        expected_message = (
+            "'my string' is an instance of <class 'str'>, "
+            "expected <class 'int'>")
         if sys.version_info[0] < 3:
             expected_message = expected_message.replace("class", "type")
         with _assert_raises_assertion(expected_message):
             assert_is_instance("my string", int)
 
-    def test_assert_is_instance__custom_message(self):
+    def test_assert_not_is_instance(self):
+        assert_not_is_instance(4, str)
+        assert_not_is_instance(4, (str, bytes))
         with _assert_raises_assertion("my message"):
-            assert_is_instance("my string", int, msg="my message")
+            assert_not_is_instance(OSError(), Exception, msg="my message")
+
+    def test_assert_not_is_instance__default_message(self):
+        expected_message = "OSError() is an instance of <class 'OSError'>"
+        if sys.version_info[0] < 3:
+            expected_message = expected_message.replace("class", "type")
+            expected_message = expected_message.replace(
+                "type 'OSError'", "type 'exceptions.OSError'")
+        with _assert_raises_assertion(expected_message):
+            assert_not_is_instance(OSError(), Exception)
 
     def test_assert_has_attr__has_attribute(self):
         d = _DummyObject()