1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/python/mock-1.0.0/html/_sources/mock.txt Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,842 @@
1.4 +The Mock Class
1.5 +==============
1.6 +
1.7 +.. currentmodule:: mock
1.8 +
1.9 +.. testsetup::
1.10 +
1.11 + class SomeClass:
1.12 + pass
1.13 +
1.14 +
1.15 +`Mock` is a flexible mock object intended to replace the use of stubs and
1.16 +test doubles throughout your code. Mocks are callable and create attributes as
1.17 +new mocks when you access them [#]_. Accessing the same attribute will always
1.18 +return the same mock. Mocks record how you use them, allowing you to make
1.19 +assertions about what your code has done to them.
1.20 +
1.21 +:class:`MagicMock` is a subclass of `Mock` with all the magic methods
1.22 +pre-created and ready to use. There are also non-callable variants, useful
1.23 +when you are mocking out objects that aren't callable:
1.24 +:class:`NonCallableMock` and :class:`NonCallableMagicMock`
1.25 +
1.26 +The :func:`patch` decorators makes it easy to temporarily replace classes
1.27 +in a particular module with a `Mock` object. By default `patch` will create
1.28 +a `MagicMock` for you. You can specify an alternative class of `Mock` using
1.29 +the `new_callable` argument to `patch`.
1.30 +
1.31 +
1.32 +.. index:: side_effect
1.33 +.. index:: return_value
1.34 +.. index:: wraps
1.35 +.. index:: name
1.36 +.. index:: spec
1.37 +
1.38 +.. class:: Mock(spec=None, side_effect=None, return_value=DEFAULT, wraps=None, name=None, spec_set=None, **kwargs)
1.39 +
1.40 + Create a new `Mock` object. `Mock` takes several optional arguments
1.41 + that specify the behaviour of the Mock object:
1.42 +
1.43 + * `spec`: This can be either a list of strings or an existing object (a
1.44 + class or instance) that acts as the specification for the mock object. If
1.45 + you pass in an object then a list of strings is formed by calling dir on
1.46 + the object (excluding unsupported magic attributes and methods).
1.47 + Accessing any attribute not in this list will raise an `AttributeError`.
1.48 +
1.49 + If `spec` is an object (rather than a list of strings) then
1.50 + :attr:`__class__` returns the class of the spec object. This allows mocks
1.51 + to pass `isinstance` tests.
1.52 +
1.53 + * `spec_set`: A stricter variant of `spec`. If used, attempting to *set*
1.54 + or get an attribute on the mock that isn't on the object passed as
1.55 + `spec_set` will raise an `AttributeError`.
1.56 +
1.57 + * `side_effect`: A function to be called whenever the Mock is called. See
1.58 + the :attr:`~Mock.side_effect` attribute. Useful for raising exceptions or
1.59 + dynamically changing return values. The function is called with the same
1.60 + arguments as the mock, and unless it returns :data:`DEFAULT`, the return
1.61 + value of this function is used as the return value.
1.62 +
1.63 + Alternatively `side_effect` can be an exception class or instance. In
1.64 + this case the exception will be raised when the mock is called.
1.65 +
1.66 + If `side_effect` is an iterable then each call to the mock will return
1.67 + the next value from the iterable. If any of the members of the iterable
1.68 + are exceptions they will be raised instead of returned.
1.69 +
1.70 + A `side_effect` can be cleared by setting it to `None`.
1.71 +
1.72 + * `return_value`: The value returned when the mock is called. By default
1.73 + this is a new Mock (created on first access). See the
1.74 + :attr:`return_value` attribute.
1.75 +
1.76 + * `wraps`: Item for the mock object to wrap. If `wraps` is not None then
1.77 + calling the Mock will pass the call through to the wrapped object
1.78 + (returning the real result and ignoring `return_value`). Attribute access
1.79 + on the mock will return a Mock object that wraps the corresponding
1.80 + attribute of the wrapped object (so attempting to access an attribute
1.81 + that doesn't exist will raise an `AttributeError`).
1.82 +
1.83 + If the mock has an explicit `return_value` set then calls are not passed
1.84 + to the wrapped object and the `return_value` is returned instead.
1.85 +
1.86 + * `name`: If the mock has a name then it will be used in the repr of the
1.87 + mock. This can be useful for debugging. The name is propagated to child
1.88 + mocks.
1.89 +
1.90 + Mocks can also be called with arbitrary keyword arguments. These will be
1.91 + used to set attributes on the mock after it is created. See the
1.92 + :meth:`configure_mock` method for details.
1.93 +
1.94 +
1.95 + .. method:: assert_called_with(*args, **kwargs)
1.96 +
1.97 + This method is a convenient way of asserting that calls are made in a
1.98 + particular way:
1.99 +
1.100 + .. doctest::
1.101 +
1.102 + >>> mock = Mock()
1.103 + >>> mock.method(1, 2, 3, test='wow')
1.104 + <Mock name='mock.method()' id='...'>
1.105 + >>> mock.method.assert_called_with(1, 2, 3, test='wow')
1.106 +
1.107 +
1.108 + .. method:: assert_called_once_with(*args, **kwargs)
1.109 +
1.110 + Assert that the mock was called exactly once and with the specified
1.111 + arguments.
1.112 +
1.113 + .. doctest::
1.114 +
1.115 + >>> mock = Mock(return_value=None)
1.116 + >>> mock('foo', bar='baz')
1.117 + >>> mock.assert_called_once_with('foo', bar='baz')
1.118 + >>> mock('foo', bar='baz')
1.119 + >>> mock.assert_called_once_with('foo', bar='baz')
1.120 + Traceback (most recent call last):
1.121 + ...
1.122 + AssertionError: Expected to be called once. Called 2 times.
1.123 +
1.124 +
1.125 + .. method:: assert_any_call(*args, **kwargs)
1.126 +
1.127 + assert the mock has been called with the specified arguments.
1.128 +
1.129 + The assert passes if the mock has *ever* been called, unlike
1.130 + :meth:`assert_called_with` and :meth:`assert_called_once_with` that
1.131 + only pass if the call is the most recent one.
1.132 +
1.133 + .. doctest::
1.134 +
1.135 + >>> mock = Mock(return_value=None)
1.136 + >>> mock(1, 2, arg='thing')
1.137 + >>> mock('some', 'thing', 'else')
1.138 + >>> mock.assert_any_call(1, 2, arg='thing')
1.139 +
1.140 +
1.141 + .. method:: assert_has_calls(calls, any_order=False)
1.142 +
1.143 + assert the mock has been called with the specified calls.
1.144 + The `mock_calls` list is checked for the calls.
1.145 +
1.146 + If `any_order` is False (the default) then the calls must be
1.147 + sequential. There can be extra calls before or after the
1.148 + specified calls.
1.149 +
1.150 + If `any_order` is True then the calls can be in any order, but
1.151 + they must all appear in :attr:`mock_calls`.
1.152 +
1.153 + .. doctest::
1.154 +
1.155 + >>> mock = Mock(return_value=None)
1.156 + >>> mock(1)
1.157 + >>> mock(2)
1.158 + >>> mock(3)
1.159 + >>> mock(4)
1.160 + >>> calls = [call(2), call(3)]
1.161 + >>> mock.assert_has_calls(calls)
1.162 + >>> calls = [call(4), call(2), call(3)]
1.163 + >>> mock.assert_has_calls(calls, any_order=True)
1.164 +
1.165 +
1.166 + .. method:: reset_mock()
1.167 +
1.168 + The reset_mock method resets all the call attributes on a mock object:
1.169 +
1.170 + .. doctest::
1.171 +
1.172 + >>> mock = Mock(return_value=None)
1.173 + >>> mock('hello')
1.174 + >>> mock.called
1.175 + True
1.176 + >>> mock.reset_mock()
1.177 + >>> mock.called
1.178 + False
1.179 +
1.180 + This can be useful where you want to make a series of assertions that
1.181 + reuse the same object. Note that `reset_mock` *doesn't* clear the
1.182 + return value, :attr:`side_effect` or any child attributes you have
1.183 + set using normal assignment. Child mocks and the return value mock
1.184 + (if any) are reset as well.
1.185 +
1.186 +
1.187 + .. method:: mock_add_spec(spec, spec_set=False)
1.188 +
1.189 + Add a spec to a mock. `spec` can either be an object or a
1.190 + list of strings. Only attributes on the `spec` can be fetched as
1.191 + attributes from the mock.
1.192 +
1.193 + If `spec_set` is `True` then only attributes on the spec can be set.
1.194 +
1.195 +
1.196 + .. method:: attach_mock(mock, attribute)
1.197 +
1.198 + Attach a mock as an attribute of this one, replacing its name and
1.199 + parent. Calls to the attached mock will be recorded in the
1.200 + :attr:`method_calls` and :attr:`mock_calls` attributes of this one.
1.201 +
1.202 +
1.203 + .. method:: configure_mock(**kwargs)
1.204 +
1.205 + Set attributes on the mock through keyword arguments.
1.206 +
1.207 + Attributes plus return values and side effects can be set on child
1.208 + mocks using standard dot notation and unpacking a dictionary in the
1.209 + method call:
1.210 +
1.211 + .. doctest::
1.212 +
1.213 + >>> mock = Mock()
1.214 + >>> attrs = {'method.return_value': 3, 'other.side_effect': KeyError}
1.215 + >>> mock.configure_mock(**attrs)
1.216 + >>> mock.method()
1.217 + 3
1.218 + >>> mock.other()
1.219 + Traceback (most recent call last):
1.220 + ...
1.221 + KeyError
1.222 +
1.223 + The same thing can be achieved in the constructor call to mocks:
1.224 +
1.225 + .. doctest::
1.226 +
1.227 + >>> attrs = {'method.return_value': 3, 'other.side_effect': KeyError}
1.228 + >>> mock = Mock(some_attribute='eggs', **attrs)
1.229 + >>> mock.some_attribute
1.230 + 'eggs'
1.231 + >>> mock.method()
1.232 + 3
1.233 + >>> mock.other()
1.234 + Traceback (most recent call last):
1.235 + ...
1.236 + KeyError
1.237 +
1.238 + `configure_mock` exists to make it easier to do configuration
1.239 + after the mock has been created.
1.240 +
1.241 +
1.242 + .. method:: __dir__()
1.243 +
1.244 + `Mock` objects limit the results of `dir(some_mock)` to useful results.
1.245 + For mocks with a `spec` this includes all the permitted attributes
1.246 + for the mock.
1.247 +
1.248 + See :data:`FILTER_DIR` for what this filtering does, and how to
1.249 + switch it off.
1.250 +
1.251 +
1.252 + .. method:: _get_child_mock(**kw)
1.253 +
1.254 + Create the child mocks for attributes and return value.
1.255 + By default child mocks will be the same type as the parent.
1.256 + Subclasses of Mock may want to override this to customize the way
1.257 + child mocks are made.
1.258 +
1.259 + For non-callable mocks the callable variant will be used (rather than
1.260 + any custom subclass).
1.261 +
1.262 +
1.263 + .. attribute:: called
1.264 +
1.265 + A boolean representing whether or not the mock object has been called:
1.266 +
1.267 + .. doctest::
1.268 +
1.269 + >>> mock = Mock(return_value=None)
1.270 + >>> mock.called
1.271 + False
1.272 + >>> mock()
1.273 + >>> mock.called
1.274 + True
1.275 +
1.276 + .. attribute:: call_count
1.277 +
1.278 + An integer telling you how many times the mock object has been called:
1.279 +
1.280 + .. doctest::
1.281 +
1.282 + >>> mock = Mock(return_value=None)
1.283 + >>> mock.call_count
1.284 + 0
1.285 + >>> mock()
1.286 + >>> mock()
1.287 + >>> mock.call_count
1.288 + 2
1.289 +
1.290 +
1.291 + .. attribute:: return_value
1.292 +
1.293 + Set this to configure the value returned by calling the mock:
1.294 +
1.295 + .. doctest::
1.296 +
1.297 + >>> mock = Mock()
1.298 + >>> mock.return_value = 'fish'
1.299 + >>> mock()
1.300 + 'fish'
1.301 +
1.302 + The default return value is a mock object and you can configure it in
1.303 + the normal way:
1.304 +
1.305 + .. doctest::
1.306 +
1.307 + >>> mock = Mock()
1.308 + >>> mock.return_value.attribute = sentinel.Attribute
1.309 + >>> mock.return_value()
1.310 + <Mock name='mock()()' id='...'>
1.311 + >>> mock.return_value.assert_called_with()
1.312 +
1.313 + `return_value` can also be set in the constructor:
1.314 +
1.315 + .. doctest::
1.316 +
1.317 + >>> mock = Mock(return_value=3)
1.318 + >>> mock.return_value
1.319 + 3
1.320 + >>> mock()
1.321 + 3
1.322 +
1.323 +
1.324 + .. attribute:: side_effect
1.325 +
1.326 + This can either be a function to be called when the mock is called,
1.327 + or an exception (class or instance) to be raised.
1.328 +
1.329 + If you pass in a function it will be called with same arguments as the
1.330 + mock and unless the function returns the :data:`DEFAULT` singleton the
1.331 + call to the mock will then return whatever the function returns. If the
1.332 + function returns :data:`DEFAULT` then the mock will return its normal
1.333 + value (from the :attr:`return_value`.
1.334 +
1.335 + An example of a mock that raises an exception (to test exception
1.336 + handling of an API):
1.337 +
1.338 + .. doctest::
1.339 +
1.340 + >>> mock = Mock()
1.341 + >>> mock.side_effect = Exception('Boom!')
1.342 + >>> mock()
1.343 + Traceback (most recent call last):
1.344 + ...
1.345 + Exception: Boom!
1.346 +
1.347 + Using `side_effect` to return a sequence of values:
1.348 +
1.349 + .. doctest::
1.350 +
1.351 + >>> mock = Mock()
1.352 + >>> mock.side_effect = [3, 2, 1]
1.353 + >>> mock(), mock(), mock()
1.354 + (3, 2, 1)
1.355 +
1.356 + The `side_effect` function is called with the same arguments as the
1.357 + mock (so it is wise for it to take arbitrary args and keyword
1.358 + arguments) and whatever it returns is used as the return value for
1.359 + the call. The exception is if `side_effect` returns :data:`DEFAULT`,
1.360 + in which case the normal :attr:`return_value` is used.
1.361 +
1.362 + .. doctest::
1.363 +
1.364 + >>> mock = Mock(return_value=3)
1.365 + >>> def side_effect(*args, **kwargs):
1.366 + ... return DEFAULT
1.367 + ...
1.368 + >>> mock.side_effect = side_effect
1.369 + >>> mock()
1.370 + 3
1.371 +
1.372 + `side_effect` can be set in the constructor. Here's an example that
1.373 + adds one to the value the mock is called with and returns it:
1.374 +
1.375 + .. doctest::
1.376 +
1.377 + >>> side_effect = lambda value: value + 1
1.378 + >>> mock = Mock(side_effect=side_effect)
1.379 + >>> mock(3)
1.380 + 4
1.381 + >>> mock(-8)
1.382 + -7
1.383 +
1.384 + Setting `side_effect` to `None` clears it:
1.385 +
1.386 + .. doctest::
1.387 +
1.388 + >>> from mock import Mock
1.389 + >>> m = Mock(side_effect=KeyError, return_value=3)
1.390 + >>> m()
1.391 + Traceback (most recent call last):
1.392 + ...
1.393 + KeyError
1.394 + >>> m.side_effect = None
1.395 + >>> m()
1.396 + 3
1.397 +
1.398 +
1.399 + .. attribute:: call_args
1.400 +
1.401 + This is either `None` (if the mock hasn't been called), or the
1.402 + arguments that the mock was last called with. This will be in the
1.403 + form of a tuple: the first member is any ordered arguments the mock
1.404 + was called with (or an empty tuple) and the second member is any
1.405 + keyword arguments (or an empty dictionary).
1.406 +
1.407 + .. doctest::
1.408 +
1.409 + >>> mock = Mock(return_value=None)
1.410 + >>> print mock.call_args
1.411 + None
1.412 + >>> mock()
1.413 + >>> mock.call_args
1.414 + call()
1.415 + >>> mock.call_args == ()
1.416 + True
1.417 + >>> mock(3, 4)
1.418 + >>> mock.call_args
1.419 + call(3, 4)
1.420 + >>> mock.call_args == ((3, 4),)
1.421 + True
1.422 + >>> mock(3, 4, 5, key='fish', next='w00t!')
1.423 + >>> mock.call_args
1.424 + call(3, 4, 5, key='fish', next='w00t!')
1.425 +
1.426 + `call_args`, along with members of the lists :attr:`call_args_list`,
1.427 + :attr:`method_calls` and :attr:`mock_calls` are :data:`call` objects.
1.428 + These are tuples, so they can be unpacked to get at the individual
1.429 + arguments and make more complex assertions. See
1.430 + :ref:`calls as tuples <calls-as-tuples>`.
1.431 +
1.432 +
1.433 + .. attribute:: call_args_list
1.434 +
1.435 + This is a list of all the calls made to the mock object in sequence
1.436 + (so the length of the list is the number of times it has been
1.437 + called). Before any calls have been made it is an empty list. The
1.438 + :data:`call` object can be used for conveniently constructing lists of
1.439 + calls to compare with `call_args_list`.
1.440 +
1.441 + .. doctest::
1.442 +
1.443 + >>> mock = Mock(return_value=None)
1.444 + >>> mock()
1.445 + >>> mock(3, 4)
1.446 + >>> mock(key='fish', next='w00t!')
1.447 + >>> mock.call_args_list
1.448 + [call(), call(3, 4), call(key='fish', next='w00t!')]
1.449 + >>> expected = [(), ((3, 4),), ({'key': 'fish', 'next': 'w00t!'},)]
1.450 + >>> mock.call_args_list == expected
1.451 + True
1.452 +
1.453 + Members of `call_args_list` are :data:`call` objects. These can be
1.454 + unpacked as tuples to get at the individual arguments. See
1.455 + :ref:`calls as tuples <calls-as-tuples>`.
1.456 +
1.457 +
1.458 + .. attribute:: method_calls
1.459 +
1.460 + As well as tracking calls to themselves, mocks also track calls to
1.461 + methods and attributes, and *their* methods and attributes:
1.462 +
1.463 + .. doctest::
1.464 +
1.465 + >>> mock = Mock()
1.466 + >>> mock.method()
1.467 + <Mock name='mock.method()' id='...'>
1.468 + >>> mock.property.method.attribute()
1.469 + <Mock name='mock.property.method.attribute()' id='...'>
1.470 + >>> mock.method_calls
1.471 + [call.method(), call.property.method.attribute()]
1.472 +
1.473 + Members of `method_calls` are :data:`call` objects. These can be
1.474 + unpacked as tuples to get at the individual arguments. See
1.475 + :ref:`calls as tuples <calls-as-tuples>`.
1.476 +
1.477 +
1.478 + .. attribute:: mock_calls
1.479 +
1.480 + `mock_calls` records *all* calls to the mock object, its methods, magic
1.481 + methods *and* return value mocks.
1.482 +
1.483 + .. doctest::
1.484 +
1.485 + >>> mock = MagicMock()
1.486 + >>> result = mock(1, 2, 3)
1.487 + >>> mock.first(a=3)
1.488 + <MagicMock name='mock.first()' id='...'>
1.489 + >>> mock.second()
1.490 + <MagicMock name='mock.second()' id='...'>
1.491 + >>> int(mock)
1.492 + 1
1.493 + >>> result(1)
1.494 + <MagicMock name='mock()()' id='...'>
1.495 + >>> expected = [call(1, 2, 3), call.first(a=3), call.second(),
1.496 + ... call.__int__(), call()(1)]
1.497 + >>> mock.mock_calls == expected
1.498 + True
1.499 +
1.500 + Members of `mock_calls` are :data:`call` objects. These can be
1.501 + unpacked as tuples to get at the individual arguments. See
1.502 + :ref:`calls as tuples <calls-as-tuples>`.
1.503 +
1.504 +
1.505 + .. attribute:: __class__
1.506 +
1.507 + Normally the `__class__` attribute of an object will return its type.
1.508 + For a mock object with a `spec` `__class__` returns the spec class
1.509 + instead. This allows mock objects to pass `isinstance` tests for the
1.510 + object they are replacing / masquerading as:
1.511 +
1.512 + .. doctest::
1.513 +
1.514 + >>> mock = Mock(spec=3)
1.515 + >>> isinstance(mock, int)
1.516 + True
1.517 +
1.518 + `__class__` is assignable to, this allows a mock to pass an
1.519 + `isinstance` check without forcing you to use a spec:
1.520 +
1.521 + .. doctest::
1.522 +
1.523 + >>> mock = Mock()
1.524 + >>> mock.__class__ = dict
1.525 + >>> isinstance(mock, dict)
1.526 + True
1.527 +
1.528 +.. class:: NonCallableMock(spec=None, wraps=None, name=None, spec_set=None, **kwargs)
1.529 +
1.530 + A non-callable version of `Mock`. The constructor parameters have the same
1.531 + meaning of `Mock`, with the exception of `return_value` and `side_effect`
1.532 + which have no meaning on a non-callable mock.
1.533 +
1.534 +Mock objects that use a class or an instance as a `spec` or `spec_set` are able
1.535 +to pass `isintance` tests:
1.536 +
1.537 +.. doctest::
1.538 +
1.539 + >>> mock = Mock(spec=SomeClass)
1.540 + >>> isinstance(mock, SomeClass)
1.541 + True
1.542 + >>> mock = Mock(spec_set=SomeClass())
1.543 + >>> isinstance(mock, SomeClass)
1.544 + True
1.545 +
1.546 +The `Mock` classes have support for mocking magic methods. See :ref:`magic
1.547 +methods <magic-methods>` for the full details.
1.548 +
1.549 +The mock classes and the :func:`patch` decorators all take arbitrary keyword
1.550 +arguments for configuration. For the `patch` decorators the keywords are
1.551 +passed to the constructor of the mock being created. The keyword arguments
1.552 +are for configuring attributes of the mock:
1.553 +
1.554 +.. doctest::
1.555 +
1.556 + >>> m = MagicMock(attribute=3, other='fish')
1.557 + >>> m.attribute
1.558 + 3
1.559 + >>> m.other
1.560 + 'fish'
1.561 +
1.562 +The return value and side effect of child mocks can be set in the same way,
1.563 +using dotted notation. As you can't use dotted names directly in a call you
1.564 +have to create a dictionary and unpack it using `**`:
1.565 +
1.566 +.. doctest::
1.567 +
1.568 + >>> attrs = {'method.return_value': 3, 'other.side_effect': KeyError}
1.569 + >>> mock = Mock(some_attribute='eggs', **attrs)
1.570 + >>> mock.some_attribute
1.571 + 'eggs'
1.572 + >>> mock.method()
1.573 + 3
1.574 + >>> mock.other()
1.575 + Traceback (most recent call last):
1.576 + ...
1.577 + KeyError
1.578 +
1.579 +
1.580 +.. class:: PropertyMock(*args, **kwargs)
1.581 +
1.582 + A mock intended to be used as a property, or other descriptor, on a class.
1.583 + `PropertyMock` provides `__get__` and `__set__` methods so you can specify
1.584 + a return value when it is fetched.
1.585 +
1.586 + Fetching a `PropertyMock` instance from an object calls the mock, with
1.587 + no args. Setting it calls the mock with the value being set.
1.588 +
1.589 + .. doctest::
1.590 +
1.591 + >>> class Foo(object):
1.592 + ... @property
1.593 + ... def foo(self):
1.594 + ... return 'something'
1.595 + ... @foo.setter
1.596 + ... def foo(self, value):
1.597 + ... pass
1.598 + ...
1.599 + >>> with patch('__main__.Foo.foo', new_callable=PropertyMock) as mock_foo:
1.600 + ... mock_foo.return_value = 'mockity-mock'
1.601 + ... this_foo = Foo()
1.602 + ... print this_foo.foo
1.603 + ... this_foo.foo = 6
1.604 + ...
1.605 + mockity-mock
1.606 + >>> mock_foo.mock_calls
1.607 + [call(), call(6)]
1.608 +
1.609 +Because of the way mock attributes are stored you can't directly attach a
1.610 +`PropertyMock` to a mock object. Instead you can attach it to the mock type
1.611 +object:
1.612 +
1.613 +.. doctest::
1.614 +
1.615 + >>> m = MagicMock()
1.616 + >>> p = PropertyMock(return_value=3)
1.617 + >>> type(m).foo = p
1.618 + >>> m.foo
1.619 + 3
1.620 + >>> p.assert_called_once_with()
1.621 +
1.622 +
1.623 +.. index:: __call__
1.624 +.. index:: calling
1.625 +
1.626 +Calling
1.627 +=======
1.628 +
1.629 +Mock objects are callable. The call will return the value set as the
1.630 +:attr:`~Mock.return_value` attribute. The default return value is a new Mock
1.631 +object; it is created the first time the return value is accessed (either
1.632 +explicitly or by calling the Mock) - but it is stored and the same one
1.633 +returned each time.
1.634 +
1.635 +Calls made to the object will be recorded in the attributes
1.636 +like :attr:`~Mock.call_args` and :attr:`~Mock.call_args_list`.
1.637 +
1.638 +If :attr:`~Mock.side_effect` is set then it will be called after the call has
1.639 +been recorded, so if `side_effect` raises an exception the call is still
1.640 +recorded.
1.641 +
1.642 +The simplest way to make a mock raise an exception when called is to make
1.643 +:attr:`~Mock.side_effect` an exception class or instance:
1.644 +
1.645 +.. doctest::
1.646 +
1.647 + >>> m = MagicMock(side_effect=IndexError)
1.648 + >>> m(1, 2, 3)
1.649 + Traceback (most recent call last):
1.650 + ...
1.651 + IndexError
1.652 + >>> m.mock_calls
1.653 + [call(1, 2, 3)]
1.654 + >>> m.side_effect = KeyError('Bang!')
1.655 + >>> m('two', 'three', 'four')
1.656 + Traceback (most recent call last):
1.657 + ...
1.658 + KeyError: 'Bang!'
1.659 + >>> m.mock_calls
1.660 + [call(1, 2, 3), call('two', 'three', 'four')]
1.661 +
1.662 +If `side_effect` is a function then whatever that function returns is what
1.663 +calls to the mock return. The `side_effect` function is called with the
1.664 +same arguments as the mock. This allows you to vary the return value of the
1.665 +call dynamically, based on the input:
1.666 +
1.667 +.. doctest::
1.668 +
1.669 + >>> def side_effect(value):
1.670 + ... return value + 1
1.671 + ...
1.672 + >>> m = MagicMock(side_effect=side_effect)
1.673 + >>> m(1)
1.674 + 2
1.675 + >>> m(2)
1.676 + 3
1.677 + >>> m.mock_calls
1.678 + [call(1), call(2)]
1.679 +
1.680 +If you want the mock to still return the default return value (a new mock), or
1.681 +any set return value, then there are two ways of doing this. Either return
1.682 +`mock.return_value` from inside `side_effect`, or return :data:`DEFAULT`:
1.683 +
1.684 +.. doctest::
1.685 +
1.686 + >>> m = MagicMock()
1.687 + >>> def side_effect(*args, **kwargs):
1.688 + ... return m.return_value
1.689 + ...
1.690 + >>> m.side_effect = side_effect
1.691 + >>> m.return_value = 3
1.692 + >>> m()
1.693 + 3
1.694 + >>> def side_effect(*args, **kwargs):
1.695 + ... return DEFAULT
1.696 + ...
1.697 + >>> m.side_effect = side_effect
1.698 + >>> m()
1.699 + 3
1.700 +
1.701 +To remove a `side_effect`, and return to the default behaviour, set the
1.702 +`side_effect` to `None`:
1.703 +
1.704 +.. doctest::
1.705 +
1.706 + >>> m = MagicMock(return_value=6)
1.707 + >>> def side_effect(*args, **kwargs):
1.708 + ... return 3
1.709 + ...
1.710 + >>> m.side_effect = side_effect
1.711 + >>> m()
1.712 + 3
1.713 + >>> m.side_effect = None
1.714 + >>> m()
1.715 + 6
1.716 +
1.717 +The `side_effect` can also be any iterable object. Repeated calls to the mock
1.718 +will return values from the iterable (until the iterable is exhausted and
1.719 +a `StopIteration` is raised):
1.720 +
1.721 +.. doctest::
1.722 +
1.723 + >>> m = MagicMock(side_effect=[1, 2, 3])
1.724 + >>> m()
1.725 + 1
1.726 + >>> m()
1.727 + 2
1.728 + >>> m()
1.729 + 3
1.730 + >>> m()
1.731 + Traceback (most recent call last):
1.732 + ...
1.733 + StopIteration
1.734 +
1.735 +If any members of the iterable are exceptions they will be raised instead of
1.736 +returned:
1.737 +
1.738 +.. doctest::
1.739 +
1.740 + >>> iterable = (33, ValueError, 66)
1.741 + >>> m = MagicMock(side_effect=iterable)
1.742 + >>> m()
1.743 + 33
1.744 + >>> m()
1.745 + Traceback (most recent call last):
1.746 + ...
1.747 + ValueError
1.748 + >>> m()
1.749 + 66
1.750 +
1.751 +
1.752 +.. _deleting-attributes:
1.753 +
1.754 +Deleting Attributes
1.755 +===================
1.756 +
1.757 +Mock objects create attributes on demand. This allows them to pretend to be
1.758 +objects of any type.
1.759 +
1.760 +You may want a mock object to return `False` to a `hasattr` call, or raise an
1.761 +`AttributeError` when an attribute is fetched. You can do this by providing
1.762 +an object as a `spec` for a mock, but that isn't always convenient.
1.763 +
1.764 +You "block" attributes by deleting them. Once deleted, accessing an attribute
1.765 +will raise an `AttributeError`.
1.766 +
1.767 +.. doctest::
1.768 +
1.769 + >>> mock = MagicMock()
1.770 + >>> hasattr(mock, 'm')
1.771 + True
1.772 + >>> del mock.m
1.773 + >>> hasattr(mock, 'm')
1.774 + False
1.775 + >>> del mock.f
1.776 + >>> mock.f
1.777 + Traceback (most recent call last):
1.778 + ...
1.779 + AttributeError: f
1.780 +
1.781 +
1.782 +Attaching Mocks as Attributes
1.783 +=============================
1.784 +
1.785 +When you attach a mock as an attribute of another mock (or as the return
1.786 +value) it becomes a "child" of that mock. Calls to the child are recorded in
1.787 +the :attr:`~Mock.method_calls` and :attr:`~Mock.mock_calls` attributes of the
1.788 +parent. This is useful for configuring child mocks and then attaching them to
1.789 +the parent, or for attaching mocks to a parent that records all calls to the
1.790 +children and allows you to make assertions about the order of calls between
1.791 +mocks:
1.792 +
1.793 +.. doctest::
1.794 +
1.795 + >>> parent = MagicMock()
1.796 + >>> child1 = MagicMock(return_value=None)
1.797 + >>> child2 = MagicMock(return_value=None)
1.798 + >>> parent.child1 = child1
1.799 + >>> parent.child2 = child2
1.800 + >>> child1(1)
1.801 + >>> child2(2)
1.802 + >>> parent.mock_calls
1.803 + [call.child1(1), call.child2(2)]
1.804 +
1.805 +The exception to this is if the mock has a name. This allows you to prevent
1.806 +the "parenting" if for some reason you don't want it to happen.
1.807 +
1.808 +.. doctest::
1.809 +
1.810 + >>> mock = MagicMock()
1.811 + >>> not_a_child = MagicMock(name='not-a-child')
1.812 + >>> mock.attribute = not_a_child
1.813 + >>> mock.attribute()
1.814 + <MagicMock name='not-a-child()' id='...'>
1.815 + >>> mock.mock_calls
1.816 + []
1.817 +
1.818 +Mocks created for you by :func:`patch` are automatically given names. To
1.819 +attach mocks that have names to a parent you use the :meth:`~Mock.attach_mock`
1.820 +method:
1.821 +
1.822 +.. doctest::
1.823 +
1.824 + >>> thing1 = object()
1.825 + >>> thing2 = object()
1.826 + >>> parent = MagicMock()
1.827 + >>> with patch('__main__.thing1', return_value=None) as child1:
1.828 + ... with patch('__main__.thing2', return_value=None) as child2:
1.829 + ... parent.attach_mock(child1, 'child1')
1.830 + ... parent.attach_mock(child2, 'child2')
1.831 + ... child1('one')
1.832 + ... child2('two')
1.833 + ...
1.834 + >>> parent.mock_calls
1.835 + [call.child1('one'), call.child2('two')]
1.836 +
1.837 +
1.838 +-----
1.839 +
1.840 +.. [#] The only exceptions are magic methods and attributes (those that have
1.841 + leading and trailing double underscores). Mock doesn't create these but
1.842 + instead of raises an ``AttributeError``. This is because the interpreter
1.843 + will often implicitly request these methods, and gets *very* confused to
1.844 + get a new Mock object when it expects a magic method. If you need magic
1.845 + method support see :ref:`magic methods <magic-methods>`.
