I am trying to write unit tests for Bar
that makes calls to Foo
's method read()
. I have added the patch command in setUp()
because other tests will use this patch as well.
How can I check that the read()
function was called with the arguments that I am expecting?
foo.py
class Foo(object):
def __init__(self):
self.table = {'foo': 1}
def read(self, name):
return self.table[name]
bar.py
import foo
class Bar(object):
def act(self):
a = foo.Foo()
return a.read('foo')
test_bar.py
import bar
import unittest
from mock import patch
class TestBar(unittest.TestCase):
def setUp(self):
self.foo_mock = patch('bar.foo.Foo', autospec=True).start()
self.addCleanup(patch.stopall)
def test_can_call_foo_with_correct_arguments(self):
a = bar.Bar()
a.act()
self.foo_mock.read.assert_called_once_with('foo')
python -m unittest discover
F
======================================================================
FAIL: test_can_call_foo_with_correct_arguments (test_bar.TestBar)
----------------------------------------------------------------------
Traceback (most recent call last):
File "/test_dir/test_bar.py", line 12, in test_can_call_foo_with_correct_arguments
self.foo_mock.read.assert_called_once_with('foo')
File "/usr/local/lib/python2.7/dist-packages/mock.py", line 845, in assert_called_once_with
raise AssertionError(msg)
AssertionError: Expected to be called once. Called 0 times.
----------------------------------------------------------------------
Ran 1 test in 0.001s
FAILED (failures=1)
read
is a method on instances of Foo
. You want to check for the mock return_value
to access the instance. After all, you create the instance by calling foo.Foo()
:
foo_instance = self.foo_mock.return_value
foo_instance.read.assert_called_once_with('foo')
Note that you are patching foo.Foo
; using bar.foo.Foo
is the same object, but a round-about way of specifying it.
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