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unittest.mock.rst
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:mod:`!unittest.mock` --- mock object library
=============================================
.. module:: unittest.mock
:synopsis: Mock object library.
.. moduleauthor:: Michael Foord <michael@python.org>
.. currentmodule:: unittest.mock
.. versionadded:: 3.3
**Source code:** :source:`Lib/unittest/mock.py`
--------------
:mod:`unittest.mock` is a library for testing in Python. It allows you to
replace parts of your system under test with mock objects and make assertions
about how they have been used.
:mod:`unittest.mock` provides a core :class:`Mock` class removing the need to
create a host of stubs throughout your test suite. After performing an
action, you can make assertions about which methods / attributes were used
and arguments they were called with. You can also specify return values and
set needed attributes in the normal way.
Additionally, mock provides a :func:`patch` decorator that handles patching
module and class level attributes within the scope of a test, along with
:const:`sentinel` for creating unique objects. See the `quick guide`_ for
some examples of how to use :class:`Mock`, :class:`MagicMock` and
:func:`patch`.
Mock is designed for use with :mod:`unittest` and
is based on the 'action -> assertion' pattern instead of 'record -> replay'
used by many mocking frameworks.
There is a backport of :mod:`unittest.mock` for earlier versions of Python,
available as :pypi:`mock` on PyPI.
Quick Guide
-----------
.. testsetup::
class ProductionClass:
def method(self, a, b, c):
pass
class SomeClass:
@staticmethod
def static_method(args):
return args
@classmethod
def class_method(cls, args):
return args
:class:`Mock` and :class:`MagicMock` objects create all attributes and
methods as you access them and store details of how they have been used. You
can configure them, to specify return values or limit what attributes are
available, and then make assertions about how they have been used:
>>> from unittest.mock import MagicMock
>>> thing = ProductionClass()
>>> thing.method = MagicMock(return_value=3)
>>> thing.method(3, 4, 5, key='value')
3
>>> thing.method.assert_called_with(3, 4, 5, key='value')
:attr:`side_effect` allows you to perform side effects, including raising an
exception when a mock is called:
>>> from unittest.mock import Mock
>>> mock = Mock(side_effect=KeyError('foo'))
>>> mock()
Traceback (most recent call last):
...
KeyError: 'foo'
>>> values = {'a': 1, 'b': 2, 'c': 3}
>>> def side_effect(arg):
... return values[arg]
...
>>> mock.side_effect = side_effect
>>> mock('a'), mock('b'), mock('c')
(1, 2, 3)
>>> mock.side_effect = [5, 4, 3, 2, 1]
>>> mock(), mock(), mock()
(5, 4, 3)
Mock has many other ways you can configure it and control its behaviour. For
example the *spec* argument configures the mock to take its specification
from another object. Attempting to access attributes or methods on the mock
that don't exist on the spec will fail with an :exc:`AttributeError`.
The :func:`patch` decorator / context manager makes it easy to mock classes or
objects in a module under test. The object you specify will be replaced with a
mock (or other object) during the test and restored when the test ends::
>>> from unittest.mock import patch
>>> @patch('module.ClassName2')
... @patch('module.ClassName1')
... def test(MockClass1, MockClass2):
... module.ClassName1()
... module.ClassName2()
... assert MockClass1 is module.ClassName1
... assert MockClass2 is module.ClassName2
... assert MockClass1.called
... assert MockClass2.called
...
>>> test()
.. note::
When you nest patch decorators the mocks are passed in to the decorated
function in the same order they applied (the normal *Python* order that
decorators are applied). This means from the bottom up, so in the example
above the mock for ``module.ClassName1`` is passed in first.
With :func:`patch` it matters that you patch objects in the namespace where they
are looked up. This is normally straightforward, but for a quick guide
read :ref:`where to patch <where-to-patch>`.
As well as a decorator :func:`patch` can be used as a context manager in a with
statement:
>>> with patch.object(ProductionClass, 'method', return_value=None) as mock_method:
... thing = ProductionClass()
... thing.method(1, 2, 3)
...
>>> mock_method.assert_called_once_with(1, 2, 3)
There is also :func:`patch.dict` for setting values in a dictionary just
during a scope and restoring the dictionary to its original state when the test
ends:
>>> foo = {'key': 'value'}
>>> original = foo.copy()
>>> with patch.dict(foo, {'newkey': 'newvalue'}, clear=True):
... assert foo == {'newkey': 'newvalue'}
...
>>> assert foo == original
Mock supports the mocking of Python :ref:`magic methods <magic-methods>`. The
easiest way of using magic methods is with the :class:`MagicMock` class. It
allows you to do things like:
>>> mock = MagicMock()
>>> mock.__str__.return_value = 'foobarbaz'
>>> str(mock)
'foobarbaz'
>>> mock.__str__.assert_called_with()
Mock allows you to assign functions (or other Mock instances) to magic methods
and they will be called appropriately. The :class:`MagicMock` class is just a Mock
variant that has all of the magic methods pre-created for you (well, all the
useful ones anyway).
The following is an example of using magic methods with the ordinary Mock
class:
>>> mock = Mock()
>>> mock.__str__ = Mock(return_value='wheeeeee')
>>> str(mock)
'wheeeeee'
For ensuring that the mock objects in your tests have the same api as the
objects they are replacing, you can use :ref:`auto-speccing <auto-speccing>`.
Auto-speccing can be done through the *autospec* argument to patch, or the
:func:`create_autospec` function. Auto-speccing creates mock objects that
have the same attributes and methods as the objects they are replacing, and
any functions and methods (including constructors) have the same call
signature as the real object.
This ensures that your mocks will fail in the same way as your production
code if they are used incorrectly:
>>> from unittest.mock import create_autospec
>>> def function(a, b, c):
... pass
...
>>> mock_function = create_autospec(function, return_value='fishy')
>>> mock_function(1, 2, 3)
'fishy'
>>> mock_function.assert_called_once_with(1, 2, 3)
>>> mock_function('wrong arguments')
Traceback (most recent call last):
...
TypeError: missing a required argument: 'b'
:func:`create_autospec` can also be used on classes, where it copies the signature of
the ``__init__`` method, and on callable objects where it copies the signature of
the ``__call__`` method.
The Mock Class
--------------
.. testsetup::
import asyncio
import inspect
import unittest
import threading
from unittest.mock import sentinel, DEFAULT, ANY
from unittest.mock import patch, call, Mock, MagicMock, PropertyMock, AsyncMock
from unittest.mock import ThreadingMock
from unittest.mock import mock_open
:class:`Mock` is a flexible mock object intended to replace the use of stubs and
test doubles throughout your code. Mocks are callable and create attributes as
new mocks when you access them [#]_. Accessing the same attribute will always
return the same mock. Mocks record how you use them, allowing you to make
assertions about what your code has done to them.
:class:`MagicMock` is a subclass of :class:`Mock` with all the magic methods
pre-created and ready to use. There are also non-callable variants, useful
when you are mocking out objects that aren't callable:
:class:`NonCallableMock` and :class:`NonCallableMagicMock`
The :func:`patch` decorators makes it easy to temporarily replace classes
in a particular module with a :class:`Mock` object. By default :func:`patch` will create
a :class:`MagicMock` for you. You can specify an alternative class of :class:`Mock` using
the *new_callable* argument to :func:`patch`.
.. class:: Mock(spec=None, side_effect=None, return_value=DEFAULT, wraps=None, name=None, spec_set=None, unsafe=False, **kwargs)
Create a new :class:`Mock` object. :class:`Mock` takes several optional arguments
that specify the behaviour of the Mock object:
* *spec*: This can be either a list of strings or an existing object (a
class or instance) that acts as the specification for the mock object. If
you pass in an object then a list of strings is formed by calling dir on
the object (excluding unsupported magic attributes and methods).
Accessing any attribute not in this list will raise an :exc:`AttributeError`.
If *spec* is an object (rather than a list of strings) then
:attr:`~instance.__class__` returns the class of the spec object. This
allows mocks to pass :func:`isinstance` tests.
* *spec_set*: A stricter variant of *spec*. If used, attempting to *set*
or get an attribute on the mock that isn't on the object passed as
*spec_set* will raise an :exc:`AttributeError`.
* *side_effect*: A function to be called whenever the Mock is called. See
the :attr:`~Mock.side_effect` attribute. Useful for raising exceptions or
dynamically changing return values. The function is called with the same
arguments as the mock, and unless it returns :data:`DEFAULT`, the return
value of this function is used as the return value.
Alternatively *side_effect* can be an exception class or instance. In
this case the exception will be raised when the mock is called.
If *side_effect* is an iterable then each call to the mock will return
the next value from the iterable.
A *side_effect* can be cleared by setting it to ``None``.
* *return_value*: The value returned when the mock is called. By default
this is a new Mock (created on first access). See the
:attr:`return_value` attribute.
* *unsafe*: By default, accessing any attribute whose name starts with
*assert*, *assret*, *asert*, *aseert* or *assrt* will raise an
:exc:`AttributeError`. Passing ``unsafe=True`` will allow access to
these attributes.
.. versionadded:: 3.5
* *wraps*: Item for the mock object to wrap. If *wraps* is not ``None`` then
calling the Mock will pass the call through to the wrapped object
(returning the real result). Attribute access on the mock will return a
Mock object that wraps the corresponding attribute of the wrapped
object (so attempting to access an attribute that doesn't exist will
raise an :exc:`AttributeError`).
If the mock has an explicit *return_value* set then calls are not passed
to the wrapped object and the *return_value* is returned instead.
* *name*: If the mock has a name then it will be used in the repr of the
mock. This can be useful for debugging. The name is propagated to child
mocks.
Mocks can also be called with arbitrary keyword arguments. These will be
used to set attributes on the mock after it is created. See the
:meth:`configure_mock` method for details.
.. method:: assert_called()
Assert that the mock was called at least once.
>>> mock = Mock()
>>> mock.method()
<Mock name='mock.method()' id='...'>
>>> mock.method.assert_called()
.. versionadded:: 3.6
.. method:: assert_called_once()
Assert that the mock was called exactly once.
>>> mock = Mock()
>>> mock.method()
<Mock name='mock.method()' id='...'>
>>> mock.method.assert_called_once()
>>> mock.method()
<Mock name='mock.method()' id='...'>
>>> mock.method.assert_called_once()
Traceback (most recent call last):
...
AssertionError: Expected 'method' to have been called once. Called 2 times.
Calls: [call(), call()].
.. versionadded:: 3.6
.. method:: assert_called_with(*args, **kwargs)
This method is a convenient way of asserting that the last call has been
made in a particular way:
>>> mock = Mock()
>>> mock.method(1, 2, 3, test='wow')
<Mock name='mock.method()' id='...'>
>>> mock.method.assert_called_with(1, 2, 3, test='wow')
.. method:: assert_called_once_with(*args, **kwargs)
Assert that the mock was called exactly once and that call was with the
specified arguments.
>>> mock = Mock(return_value=None)
>>> mock('foo', bar='baz')
>>> mock.assert_called_once_with('foo', bar='baz')
>>> mock('other', bar='values')
>>> mock.assert_called_once_with('other', bar='values')
Traceback (most recent call last):
...
AssertionError: Expected 'mock' to be called once. Called 2 times.
Calls: [call('foo', bar='baz'), call('other', bar='values')].
.. method:: assert_any_call(*args, **kwargs)
assert the mock has been called with the specified arguments.
The assert passes if the mock has *ever* been called, unlike
:meth:`assert_called_with` and :meth:`assert_called_once_with` that
only pass if the call is the most recent one, and in the case of
:meth:`assert_called_once_with` it must also be the only call.
>>> mock = Mock(return_value=None)
>>> mock(1, 2, arg='thing')
>>> mock('some', 'thing', 'else')
>>> mock.assert_any_call(1, 2, arg='thing')
.. method:: assert_has_calls(calls, any_order=False)
assert the mock has been called with the specified calls.
The :attr:`mock_calls` list is checked for the calls.
If *any_order* is false then the calls must be
sequential. There can be extra calls before or after the
specified calls.
If *any_order* is true then the calls can be in any order, but
they must all appear in :attr:`mock_calls`.
>>> mock = Mock(return_value=None)
>>> mock(1)
>>> mock(2)
>>> mock(3)
>>> mock(4)
>>> calls = [call(2), call(3)]
>>> mock.assert_has_calls(calls)
>>> calls = [call(4), call(2), call(3)]
>>> mock.assert_has_calls(calls, any_order=True)
.. method:: assert_not_called()
Assert the mock was never called.
>>> m = Mock()
>>> m.hello.assert_not_called()
>>> obj = m.hello()
>>> m.hello.assert_not_called()
Traceback (most recent call last):
...
AssertionError: Expected 'hello' to not have been called. Called 1 times.
Calls: [call()].
.. versionadded:: 3.5
.. method:: reset_mock(*, return_value=False, side_effect=False)
The reset_mock method resets all the call attributes on a mock object:
>>> mock = Mock(return_value=None)
>>> mock('hello')
>>> mock.called
True
>>> mock.reset_mock()
>>> mock.called
False
.. versionchanged:: 3.6
Added two keyword-only arguments to the reset_mock function.
This can be useful where you want to make a series of assertions that
reuse the same object. Note that :meth:`reset_mock` *doesn't* clear the
return value, :attr:`side_effect` or any child attributes you have
set using normal assignment by default. In case you want to reset
*return_value* or :attr:`side_effect`, then pass the corresponding
parameter as ``True``. Child mocks and the return value mock
(if any) are reset as well.
.. note:: *return_value*, and :attr:`side_effect` are keyword-only
arguments.
.. method:: mock_add_spec(spec, spec_set=False)
Add a spec to a mock. *spec* can either be an object or a
list of strings. Only attributes on the *spec* can be fetched as
attributes from the mock.
If *spec_set* is true then only attributes on the spec can be set.
.. method:: attach_mock(mock, attribute)
Attach a mock as an attribute of this one, replacing its name and
parent. Calls to the attached mock will be recorded in the
:attr:`method_calls` and :attr:`mock_calls` attributes of this one.
.. method:: configure_mock(**kwargs)
Set attributes on the mock through keyword arguments.
Attributes plus return values and side effects can be set on child
mocks using standard dot notation and unpacking a dictionary in the
method call:
>>> mock = Mock()
>>> attrs = {'method.return_value': 3, 'other.side_effect': KeyError}
>>> mock.configure_mock(**attrs)
>>> mock.method()
3
>>> mock.other()
Traceback (most recent call last):
...
KeyError
The same thing can be achieved in the constructor call to mocks:
>>> attrs = {'method.return_value': 3, 'other.side_effect': KeyError}
>>> mock = Mock(some_attribute='eggs', **attrs)
>>> mock.some_attribute
'eggs'
>>> mock.method()
3
>>> mock.other()
Traceback (most recent call last):
...
KeyError
:meth:`configure_mock` exists to make it easier to do configuration
after the mock has been created.
.. method:: __dir__()
:class:`Mock` objects limit the results of ``dir(some_mock)`` to useful results.
For mocks with a *spec* this includes all the permitted attributes
for the mock.
See :data:`FILTER_DIR` for what this filtering does, and how to
switch it off.
.. method:: _get_child_mock(**kw)
Create the child mocks for attributes and return value.
By default child mocks will be the same type as the parent.
Subclasses of Mock may want to override this to customize the way
child mocks are made.
For non-callable mocks the callable variant will be used (rather than
any custom subclass).
.. attribute:: called
A boolean representing whether or not the mock object has been called:
>>> mock = Mock(return_value=None)
>>> mock.called
False
>>> mock()
>>> mock.called
True
.. attribute:: call_count
An integer telling you how many times the mock object has been called:
>>> mock = Mock(return_value=None)
>>> mock.call_count
0
>>> mock()
>>> mock()
>>> mock.call_count
2
.. attribute:: return_value
Set this to configure the value returned by calling the mock:
>>> mock = Mock()
>>> mock.return_value = 'fish'
>>> mock()
'fish'
The default return value is a mock object and you can configure it in
the normal way:
>>> mock = Mock()
>>> mock.return_value.attribute = sentinel.Attribute
>>> mock.return_value()
<Mock name='mock()()' id='...'>
>>> mock.return_value.assert_called_with()
:attr:`return_value` can also be set in the constructor:
>>> mock = Mock(return_value=3)
>>> mock.return_value
3
>>> mock()
3
.. attribute:: side_effect
This can either be a function to be called when the mock is called,
an iterable or an exception (class or instance) to be raised.
If you pass in a function it will be called with same arguments as the
mock and unless the function returns the :data:`DEFAULT` singleton the
call to the mock will then return whatever the function returns. If the
function returns :data:`DEFAULT` then the mock will return its normal
value (from the :attr:`return_value`).
If you pass in an iterable, it is used to retrieve an iterator which
must yield a value on every call. This value can either be an exception
instance to be raised, or a value to be returned from the call to the
mock (:data:`DEFAULT` handling is identical to the function case).
An example of a mock that raises an exception (to test exception
handling of an API):
>>> mock = Mock()
>>> mock.side_effect = Exception('Boom!')
>>> mock()
Traceback (most recent call last):
...
Exception: Boom!
Using :attr:`side_effect` to return a sequence of values:
>>> mock = Mock()
>>> mock.side_effect = [3, 2, 1]
>>> mock(), mock(), mock()
(3, 2, 1)
Using a callable:
>>> mock = Mock(return_value=3)
>>> def side_effect(*args, **kwargs):
... return DEFAULT
...
>>> mock.side_effect = side_effect
>>> mock()
3
:attr:`side_effect` can be set in the constructor. Here's an example that
adds one to the value the mock is called with and returns it:
>>> side_effect = lambda value: value + 1
>>> mock = Mock(side_effect=side_effect)
>>> mock(3)
4
>>> mock(-8)
-7
Setting :attr:`side_effect` to ``None`` clears it:
>>> m = Mock(side_effect=KeyError, return_value=3)
>>> m()
Traceback (most recent call last):
...
KeyError
>>> m.side_effect = None
>>> m()
3
.. attribute:: call_args
This is either ``None`` (if the mock hasn't been called), or the
arguments that the mock was last called with. This will be in the
form of a tuple: the first member, which can also be accessed through
the ``args`` property, is any ordered arguments the mock was
called with (or an empty tuple) and the second member, which can
also be accessed through the ``kwargs`` property, is any keyword
arguments (or an empty dictionary).
>>> mock = Mock(return_value=None)
>>> print(mock.call_args)
None
>>> mock()
>>> mock.call_args
call()
>>> mock.call_args == ()
True
>>> mock(3, 4)
>>> mock.call_args
call(3, 4)
>>> mock.call_args == ((3, 4),)
True
>>> mock.call_args.args
(3, 4)
>>> mock.call_args.kwargs
{}
>>> mock(3, 4, 5, key='fish', next='w00t!')
>>> mock.call_args
call(3, 4, 5, key='fish', next='w00t!')
>>> mock.call_args.args
(3, 4, 5)
>>> mock.call_args.kwargs
{'key': 'fish', 'next': 'w00t!'}
:attr:`call_args`, along with members of the lists :attr:`call_args_list`,
:attr:`method_calls` and :attr:`mock_calls` are :data:`call` objects.
These are tuples, so they can be unpacked to get at the individual
arguments and make more complex assertions. See
:ref:`calls as tuples <calls-as-tuples>`.
.. versionchanged:: 3.8
Added ``args`` and ``kwargs`` properties.
.. attribute:: call_args_list
This is a list of all the calls made to the mock object in sequence
(so the length of the list is the number of times it has been
called). Before any calls have been made it is an empty list. The
:data:`call` object can be used for conveniently constructing lists of
calls to compare with :attr:`call_args_list`.
>>> mock = Mock(return_value=None)
>>> mock()
>>> mock(3, 4)
>>> mock(key='fish', next='w00t!')
>>> mock.call_args_list
[call(), call(3, 4), call(key='fish', next='w00t!')]
>>> expected = [(), ((3, 4),), ({'key': 'fish', 'next': 'w00t!'},)]
>>> mock.call_args_list == expected
True
Members of :attr:`call_args_list` are :data:`call` objects. These can be
unpacked as tuples to get at the individual arguments. See
:ref:`calls as tuples <calls-as-tuples>`.
.. attribute:: method_calls
As well as tracking calls to themselves, mocks also track calls to
methods and attributes, and *their* methods and attributes:
>>> mock = Mock()
>>> mock.method()
<Mock name='mock.method()' id='...'>
>>> mock.property.method.attribute()
<Mock name='mock.property.method.attribute()' id='...'>
>>> mock.method_calls
[call.method(), call.property.method.attribute()]
Members of :attr:`method_calls` are :data:`call` objects. These can be
unpacked as tuples to get at the individual arguments. See
:ref:`calls as tuples <calls-as-tuples>`.
.. attribute:: mock_calls
:attr:`mock_calls` records *all* calls to the mock object, its methods,
magic methods *and* return value mocks.
>>> mock = MagicMock()
>>> result = mock(1, 2, 3)
>>> mock.first(a=3)
<MagicMock name='mock.first()' id='...'>
>>> mock.second()
<MagicMock name='mock.second()' id='...'>
>>> int(mock)
1
>>> result(1)
<MagicMock name='mock()()' id='...'>
>>> expected = [call(1, 2, 3), call.first(a=3), call.second(),
... call.__int__(), call()(1)]
>>> mock.mock_calls == expected
True
Members of :attr:`mock_calls` are :data:`call` objects. These can be
unpacked as tuples to get at the individual arguments. See
:ref:`calls as tuples <calls-as-tuples>`.
.. note::
The way :attr:`mock_calls` are recorded means that where nested
calls are made, the parameters of ancestor calls are not recorded
and so will always compare equal:
>>> mock = MagicMock()
>>> mock.top(a=3).bottom()
<MagicMock name='mock.top().bottom()' id='...'>
>>> mock.mock_calls
[call.top(a=3), call.top().bottom()]
>>> mock.mock_calls[-1] == call.top(a=-1).bottom()
True
.. attribute:: __class__
Normally the :attr:`__class__` attribute of an object will return its type.
For a mock object with a :attr:`spec`, ``__class__`` returns the spec class
instead. This allows mock objects to pass :func:`isinstance` tests for the
object they are replacing / masquerading as:
>>> mock = Mock(spec=3)
>>> isinstance(mock, int)
True
:attr:`__class__` is assignable to, this allows a mock to pass an
:func:`isinstance` check without forcing you to use a spec:
>>> mock = Mock()
>>> mock.__class__ = dict
>>> isinstance(mock, dict)
True
.. class:: NonCallableMock(spec=None, wraps=None, name=None, spec_set=None, **kwargs)
A non-callable version of :class:`Mock`. The constructor parameters have the same
meaning of :class:`Mock`, with the exception of *return_value* and *side_effect*
which have no meaning on a non-callable mock.
Mock objects that use a class or an instance as a :attr:`spec` or
:attr:`spec_set` are able to pass :func:`isinstance` tests:
>>> mock = Mock(spec=SomeClass)
>>> isinstance(mock, SomeClass)
True
>>> mock = Mock(spec_set=SomeClass())
>>> isinstance(mock, SomeClass)
True
The :class:`Mock` classes have support for mocking magic methods. See :ref:`magic
methods <magic-methods>` for the full details.
The mock classes and the :func:`patch` decorators all take arbitrary keyword
arguments for configuration. For the :func:`patch` decorators the keywords are
passed to the constructor of the mock being created. The keyword arguments
are for configuring attributes of the mock:
>>> m = MagicMock(attribute=3, other='fish')
>>> m.attribute
3
>>> m.other
'fish'
The return value and side effect of child mocks can be set in the same way,
using dotted notation. As you can't use dotted names directly in a call you
have to create a dictionary and unpack it using ``**``:
>>> attrs = {'method.return_value': 3, 'other.side_effect': KeyError}
>>> mock = Mock(some_attribute='eggs', **attrs)
>>> mock.some_attribute
'eggs'
>>> mock.method()
3
>>> mock.other()
Traceback (most recent call last):
...
KeyError
A callable mock which was created with a *spec* (or a *spec_set*) will
introspect the specification object's signature when matching calls to
the mock. Therefore, it can match the actual call's arguments regardless
of whether they were passed positionally or by name::
>>> def f(a, b, c): pass
...
>>> mock = Mock(spec=f)
>>> mock(1, 2, c=3)
<Mock name='mock()' id='140161580456576'>
>>> mock.assert_called_with(1, 2, 3)
>>> mock.assert_called_with(a=1, b=2, c=3)
This applies to :meth:`~Mock.assert_called_with`,
:meth:`~Mock.assert_called_once_with`, :meth:`~Mock.assert_has_calls` and
:meth:`~Mock.assert_any_call`. When :ref:`auto-speccing`, it will also
apply to method calls on the mock object.
.. versionchanged:: 3.4
Added signature introspection on specced and autospecced mock objects.
.. class:: PropertyMock(*args, **kwargs)
A mock intended to be used as a :class:`property`, or other
:term:`descriptor`, on a class. :class:`PropertyMock` provides
:meth:`~object.__get__` and :meth:`~object.__set__` methods
so you can specify a return value when it is fetched.
Fetching a :class:`PropertyMock` instance from an object calls the mock, with
no args. Setting it calls the mock with the value being set. ::
>>> class Foo:
... @property
... def foo(self):
... return 'something'
... @foo.setter
... def foo(self, value):
... pass
...
>>> with patch('__main__.Foo.foo', new_callable=PropertyMock) as mock_foo:
... mock_foo.return_value = 'mockity-mock'
... this_foo = Foo()
... print(this_foo.foo)
... this_foo.foo = 6
...
mockity-mock
>>> mock_foo.mock_calls
[call(), call(6)]
Because of the way mock attributes are stored you can't directly attach a
:class:`PropertyMock` to a mock object. Instead you can attach it to the mock type
object::
>>> m = MagicMock()
>>> p = PropertyMock(return_value=3)
>>> type(m).foo = p
>>> m.foo
3
>>> p.assert_called_once_with()
.. class:: AsyncMock(spec=None, side_effect=None, return_value=DEFAULT, wraps=None, name=None, spec_set=None, unsafe=False, **kwargs)
An asynchronous version of :class:`MagicMock`. The :class:`AsyncMock` object will
behave so the object is recognized as an async function, and the result of a
call is an awaitable.
>>> mock = AsyncMock()
>>> asyncio.iscoroutinefunction(mock)
True
>>> inspect.isawaitable(mock()) # doctest: +SKIP
True
The result of ``mock()`` is an async function which will have the outcome
of ``side_effect`` or ``return_value`` after it has been awaited:
- if ``side_effect`` is a function, the async function will return the
result of that function,
- if ``side_effect`` is an exception, the async function will raise the
exception,
- if ``side_effect`` is an iterable, the async function will return the
next value of the iterable, however, if the sequence of result is
exhausted, ``StopAsyncIteration`` is raised immediately,
- if ``side_effect`` is not defined, the async function will return the
value defined by ``return_value``, hence, by default, the async function
returns a new :class:`AsyncMock` object.
Setting the *spec* of a :class:`Mock` or :class:`MagicMock` to an async function
will result in a coroutine object being returned after calling.
>>> async def async_func(): pass
...
>>> mock = MagicMock(async_func)
>>> mock
<MagicMock spec='function' id='...'>
>>> mock() # doctest: +SKIP
<coroutine object AsyncMockMixin._mock_call at ...>
Setting the *spec* of a :class:`Mock`, :class:`MagicMock`, or :class:`AsyncMock`
to a class with asynchronous and synchronous functions will automatically
detect the synchronous functions and set them as :class:`MagicMock` (if the
parent mock is :class:`AsyncMock` or :class:`MagicMock`) or :class:`Mock` (if
the parent mock is :class:`Mock`). All asynchronous functions will be
:class:`AsyncMock`.
>>> class ExampleClass:
... def sync_foo():
... pass
... async def async_foo():
... pass
...
>>> a_mock = AsyncMock(ExampleClass)
>>> a_mock.sync_foo
<MagicMock name='mock.sync_foo' id='...'>
>>> a_mock.async_foo
<AsyncMock name='mock.async_foo' id='...'>
>>> mock = Mock(ExampleClass)
>>> mock.sync_foo
<Mock name='mock.sync_foo' id='...'>
>>> mock.async_foo
<AsyncMock name='mock.async_foo' id='...'>
.. versionadded:: 3.8
.. method:: assert_awaited()
Assert that the mock was awaited at least once. Note that this is separate
from the object having been called, the ``await`` keyword must be used:
>>> mock = AsyncMock()
>>> async def main(coroutine_mock):
... await coroutine_mock
...
>>> coroutine_mock = mock()
>>> mock.called
True
>>> mock.assert_awaited()
Traceback (most recent call last):
...
AssertionError: Expected mock to have been awaited.
>>> asyncio.run(main(coroutine_mock))
>>> mock.assert_awaited()
.. method:: assert_awaited_once()
Assert that the mock was awaited exactly once.
>>> mock = AsyncMock()
>>> async def main():
... await mock()
...
>>> asyncio.run(main())
>>> mock.assert_awaited_once()
>>> asyncio.run(main())
>>> mock.assert_awaited_once()
Traceback (most recent call last):
...
AssertionError: Expected mock to have been awaited once. Awaited 2 times.
.. method:: assert_awaited_with(*args, **kwargs)
Assert that the last await was with the specified arguments.
>>> mock = AsyncMock()
>>> async def main(*args, **kwargs):
... await mock(*args, **kwargs)
...
>>> asyncio.run(main('foo', bar='bar'))
>>> mock.assert_awaited_with('foo', bar='bar')
>>> mock.assert_awaited_with('other')
Traceback (most recent call last):
...
AssertionError: expected await not found.
Expected: mock('other')
Actual: mock('foo', bar='bar')
.. method:: assert_awaited_once_with(*args, **kwargs)
Assert that the mock was awaited exactly once and with the specified
arguments.
>>> mock = AsyncMock()
>>> async def main(*args, **kwargs):
... await mock(*args, **kwargs)
...
>>> asyncio.run(main('foo', bar='bar'))
>>> mock.assert_awaited_once_with('foo', bar='bar')
>>> asyncio.run(main('foo', bar='bar'))
>>> mock.assert_awaited_once_with('foo', bar='bar')
Traceback (most recent call last):
...
AssertionError: Expected mock to have been awaited once. Awaited 2 times.
.. method:: assert_any_await(*args, **kwargs)
Assert the mock has ever been awaited with the specified arguments.