Change spy attributes to 'spy_return' and 'spy_exception' (#177)

Change spy attributes to 'spy_return' and 'spy_exception'

Author: nicoddemus

CHANGELOG.rst

@@ -1,3 +1,23 @@
+2.0.0 (2020-01-04)
+------------------
+
+Breaking Changes
+++++++++++++++++
+
+* ``mocker.spy`` attributes for tracking returned values and raised exceptions of its spied functions
+  are now called ``spy_return`` and ``spy_exception``, instead of reusing the existing
+  ``MagicMock`` attributes ``return_value`` and ``side_effect``.
+
+  Version ``1.13`` introduced a serious regression: after a spied function using ``mocker.spy``
+  raises an exception, further calls to the spy will not call the spied function,
+  always raising the first exception instead: assigning to ``side_effect`` causes
+  ``unittest.mock`` to behave this way (`#175`_).
+
+* The deprecated ``mock`` alias to the ``mocker`` fixture has finally been removed.
+
+.. _#175: https://github.com/pytest-dev/pytest-mock/issues/175
+
+
 1.13.0 (2019-12-05)
 -------------------
 

README.rst

@@ -2,10 +2,8 @@
 pytest-mock
 ===========
 
-This plugin installs a ``mocker`` fixture which is a thin-wrapper around the patching API
-provided by the `mock package <http://pypi.python.org/pypi/mock>`_,
-but with the benefit of not having to worry about undoing patches at the end
-of a test:
+This plugin provides a ``mocker`` fixture which is a thin-wrapper around the patching API
+provided by the `mock package <http://pypi.python.org/pypi/mock>`_:
 
 .. code-block:: python
 
@@ -23,6 +21,9 @@ of a test:
         os.remove.assert_called_once_with('file')
 
 
+Besides undoing the mocking automatically after the end of the test, it also provides other
+nice utilities such as ``spy`` and ``stub``, and uses pytest introspection when
+comparing calls.
 
 |python| |version| |anaconda| |ci| |coverage| |black|
 
@@ -70,7 +71,7 @@ The supported methods are:
 * `mocker.stopall <https://docs.python.org/3/library/unittest.mock.html#unittest.mock.patch.stopall>`_
 * ``mocker.resetall()``: calls `reset_mock() <https://docs.python.org/3/library/unittest.mock.html#unittest.mock.Mock.reset_mock>`_ in all mocked objects up to this point.
 
-These objects from the ``mock`` module are accessible directly from ``mocker`` for convenience:
+Also, as a convenience, these names from the ``mock`` module are accessible directly from ``mocker``:
 
 * `Mock <https://docs.python.org/3/library/unittest.mock.html#unittest.mock.Mock>`_
 * `MagicMock <https://docs.python.org/3/library/unittest.mock.html#unittest.mock.MagicMock>`_
@@ -85,33 +86,47 @@ These objects from the ``mock`` module are accessible directly from ``mocker`` f
 Spy
 ---
 
-The spy acts exactly like the original method in all cases, except it allows use of ``mock``
-features with it, like retrieving call count. It also works for class and static methods.
+The ``mocker.spy`` object acts exactly like the original method in all cases, except the spy
+also tracks method calls, return values and exceptions raised.
 
 .. code-block:: python
 
     def test_spy(mocker):
         class Foo(object):
-            def bar(self):
-                return 42
+            def bar(self, v):
+                return v * 2
 
         foo = Foo()
-        mocker.spy(foo, 'bar')
-        assert foo.bar() == 42
-        assert foo.bar.call_count == 1
+        spy = mocker.spy(foo, 'bar')
+        assert foo.bar(21) == 42
 
-Since version ``1.11``, it is also possible to query the ``return_value`` attribute
-to observe what the spied function/method returned.
+        spy.assert_called_once_with(21)
+        assert spy.spy_return == 42
 
-Since version ``1.13``, it is also possible to query the ``side_effect`` attribute
-to observe any exception thrown by the spied function/method.
+The object returned by ``mocker.spy`` is a ``MagicMock`` object, so all standard checking functions
+are available (like ``assert_called_once_with`` in the example above).
+
+In addition, spy objects contain two extra attributes:
+
+* ``spy_return``: contains the returned value of the spied function.
+* ``spy_exception``: contain the last exception value raised by the spied function/method when
+  it was last called, or ``None`` if no exception was raised.
+
+``mocker.spy`` also works for class and static methods.
+
+.. note::
+
+    In versions earlier than ``2.0``, the attributes were called ``return_value`` and
+    ``side_effect`` respectively, but due to incompatibilities with ``unittest.mock``
+    they had to be renamed (see `#175`_ for details).
+
+    .. _#175: https://github.com/pytest-dev/pytest-mock/issues/175
 
 Stub
 ----
 
-
-The stub is a mock object that accepts any arguments and is useful to test callbacks, for instance.
-May be passed a name to be used by the constructed stub object in its repr (useful for debugging).
+The stub is a mock object that accepts any arguments and is useful to test callbacks.
+It may receive an optional name that is shown in its ``repr``, useful for debugging.
 
 .. code-block:: python
 
@@ -128,7 +143,6 @@ May be passed a name to be used by the constructed stub object in its repr (usef
 Improved reporting of mock call assertion errors
 ------------------------------------------------
 
-
 This plugin monkeypatches the mock library to improve pytest output for failures
 of mock call assertions like ``Mock.assert_called_with()`` by hiding internal traceback
 entries from the ``mock`` module.

src/pytest_mock/plugin.py

@@ -113,17 +113,21 @@ def spy(self, obj, name):
 
         @w
         def wrapper(*args, **kwargs):
+            spy_obj.spy_return = None
+            spy_obj.spy_exception = None
             try:
                 r = method(*args, **kwargs)
             except Exception as e:
-                result.side_effect = e
+                spy_obj.spy_exception = e
                 raise
             else:
-                result.return_value = r
+                spy_obj.spy_return = r
             return r
 
-        result = self.patch.object(obj, name, side_effect=wrapper, autospec=autospec)
-        return result
+        spy_obj = self.patch.object(obj, name, side_effect=wrapper, autospec=autospec)
+        spy_obj.spy_return = None
+        spy_obj.spy_exception = None
+        return spy_obj
 
     def stub(self, name=None):
         """
@@ -204,19 +208,6 @@ def mocker(pytestconfig):
     result.stopall()
 
 
-@pytest.fixture
-def mock(mocker):
-    """
-    Same as "mocker", but kept only for backward compatibility.
-    """
-    import warnings
-
-    warnings.warn(
-        '"mock" fixture has been deprecated, use "mocker" instead', DeprecationWarning
-    )
-    return mocker
-
-
 _mock_module_patches = []
 _mock_module_originals = {}
 

tests/test_pytest_mock.py

@@ -132,28 +132,6 @@ def test_mock_patch_dict_resetall(mocker):
     assert x == {"new": 10}
 
 
-def test_deprecated_mock(testdir):
-    """
-    Use backward-compatibility-only mock fixture to ensure complete coverage.
-    """
-    p1 = testdir.makepyfile(
-        """
-        import os
-
-        def test(mock, tmpdir):
-            mock.patch("os.listdir", return_value=["mocked"])
-            assert os.listdir(str(tmpdir)) == ["mocked"]
-            mock.stopall()
-            assert os.listdir(str(tmpdir)) == []
-        """
-    )
-    result = testdir.runpytest(str(p1))
-    result.stdout.fnmatch_lines(
-        ['*DeprecationWarning: "mock" fixture has been deprecated, use "mocker"*']
-    )
-    assert result.ret == 0
-
-
 @pytest.mark.parametrize(
     "name",
     [
@@ -238,28 +216,52 @@ def bar(self, arg):
     assert foo.bar(arg=10) == 20
     assert other.bar(arg=10) == 20
     foo.bar.assert_called_once_with(arg=10)
-    assert foo.bar.return_value == 20
+    assert foo.bar.spy_return == 20
     spy.assert_called_once_with(arg=10)
-    assert spy.return_value == 20
+    assert spy.spy_return == 20
 
 
 def test_instance_method_spy_exception(mocker):
-    excepted_message = "foo"
-
     class Foo(object):
         def bar(self, arg):
-            raise Exception(excepted_message)
+            raise Exception("Error with {}".format(arg))
 
     foo = Foo()
-    other = Foo()
     spy = mocker.spy(foo, "bar")
 
-    with pytest.raises(Exception) as exc_info:
-        foo.bar(10)
-    assert str(exc_info.value) == excepted_message
+    expected_calls = []
+    for i, v in enumerate([10, 20]):
+        with pytest.raises(Exception, match="Error with {}".format(v)) as exc_info:
+            foo.bar(arg=v)
 
-    foo.bar.assert_called_once_with(arg=10)
-    assert spy.side_effect == exc_info.value
+        expected_calls.append(mocker.call(arg=v))
+        assert foo.bar.call_args_list == expected_calls
+        assert str(spy.spy_exception) == "Error with {}".format(v)
+
+
+def test_spy_reset(mocker):
+    class Foo(object):
+        def bar(self, x):
+            if x == 0:
+                raise ValueError("invalid x")
+            return x * 3
+
+    spy = mocker.spy(Foo, "bar")
+    assert spy.spy_return is None
+    assert spy.spy_exception is None
+
+    Foo().bar(10)
+    assert spy.spy_return == 30
+    assert spy.spy_exception is None
+
+    with pytest.raises(ValueError):
+        Foo().bar(0)
+    assert spy.spy_return is None
+    assert str(spy.spy_exception) == "invalid x"
+
+    Foo().bar(15)
+    assert spy.spy_return == 45
+    assert spy.spy_exception is None
 
 
 @skip_pypy
@@ -293,7 +295,7 @@ class Foo(Base):
     assert other.bar(arg=10) == 20
     calls = [mocker.call(foo, arg=10), mocker.call(other, arg=10)]
     assert spy.call_args_list == calls
-    assert spy.return_value == 20
+    assert spy.spy_return == 20
 
 
 @skip_pypy
@@ -306,9 +308,9 @@ def bar(cls, arg):
     spy = mocker.spy(Foo, "bar")
     assert Foo.bar(arg=10) == 20
     Foo.bar.assert_called_once_with(arg=10)
-    assert Foo.bar.return_value == 20
+    assert Foo.bar.spy_return == 20
     spy.assert_called_once_with(arg=10)
-    assert spy.return_value == 20
+    assert spy.spy_return == 20
 
 
 @skip_pypy
@@ -325,9 +327,9 @@ class Foo(Base):
     spy = mocker.spy(Foo, "bar")
     assert Foo.bar(arg=10) == 20
     Foo.bar.assert_called_once_with(arg=10)
-    assert Foo.bar.return_value == 20
+    assert Foo.bar.spy_return == 20
     spy.assert_called_once_with(arg=10)
-    assert spy.return_value == 20
+    assert spy.spy_return == 20
 
 
 @skip_pypy
@@ -346,9 +348,9 @@ def bar(cls, arg):
     spy = mocker.spy(Foo, "bar")
     assert Foo.bar(arg=10) == 20
     Foo.bar.assert_called_once_with(arg=10)
-    assert Foo.bar.return_value == 20
+    assert Foo.bar.spy_return == 20
     spy.assert_called_once_with(arg=10)
-    assert spy.return_value == 20
+    assert spy.spy_return == 20
 
 
 @skip_pypy
@@ -361,9 +363,9 @@ def bar(arg):
     spy = mocker.spy(Foo, "bar")
     assert Foo.bar(arg=10) == 20
     Foo.bar.assert_called_once_with(arg=10)
-    assert Foo.bar.return_value == 20
+    assert Foo.bar.spy_return == 20
     spy.assert_called_once_with(arg=10)
-    assert spy.return_value == 20
+    assert spy.spy_return == 20
 
 
 @skip_pypy
@@ -380,9 +382,9 @@ class Foo(Base):
     spy = mocker.spy(Foo, "bar")
     assert Foo.bar(arg=10) == 20
     Foo.bar.assert_called_once_with(arg=10)
-    assert Foo.bar.return_value == 20
+    assert Foo.bar.spy_return == 20
     spy.assert_called_once_with(arg=10)
-    assert spy.return_value == 20
+    assert spy.spy_return == 20
 
 
 def test_callable_like_spy(testdir, mocker):
@@ -402,7 +404,7 @@ def __call__(self, x):
     spy = mocker.spy(uut, "call_like")
     uut.call_like(10)
     spy.assert_called_once_with(10)
-    assert spy.return_value == 20
+    assert spy.spy_return == 20
 
 
 @contextmanager