Introduction

Here we provide some common Mox recipes that people have found useful. This section's constantly under development; if you find a better way of implementing a recipe below, please let us know in the comments.

Set up your Mox test classes in a sane way

Note: many other recipes assume you've done this.

  def setUp(self):
    self.mox = mox.Mox()

  def tearDown(self):
    self.mox.UnsetStubs()

Stub out a method called from a constructor in the same class

TODO(damien): Write a public example here.

Stub out a static method in the class under test

  def testFoo(self):

    orig_method = module.class.StaticMethod

    static_stub = staticmethod(lambda *args, **kwargs: None)
    module.class.StaticMethod = static_stub

    self.mox.ReplayAll()

    ...

    self.mox.VerifyAll()

    module.class.StaticMethod = orig_method

Mock a module-level function in a different module

  def testFoo(self):

    self.mox.StubOutWithMock(module_to_mock, 'FunctionToMock')
    module_to_mock.FunctionToMock().AndReturn(foo)

    self.mox.ReplayAll()
    ...
    self.mox.VerifyAll()

Stub out a class in a different module

TODO(damien): Write a public example here.

Mock a method in the class under test.

TODO(damien): Investigate this further. Maybe stubbing out call would help?

  def testFoo(self):

    # Note the difference: we instantiate the class *before* Replaying.
    foo_instance = module_under_test.ClassUnderTest()
    self.mox.StubOutWithMock(foo_instance, 'MethodToStub')
    foo_instance.MethodToStub().AndReturn('foo')

    ...

    self.mox.ReplayAll()
    ...
    self.mox.VerifyAll()

Mock a generator in the class under test

  def testFoo(self):

    ...

    foo_instance = module_under_test.ClassUnderTest()
    self.mox.StubOutWithMock(foo_instance, 'GeneratorToStub')

    mygen = (x for x in [1, 2, 3])
    foo_instance.MethodToStub(mox.IsA(object)).AndReturn(mygen)

    ...

    self.mox.ReplayAll()

    ...

    self.mox.VerifyAll()

Mocking datetime.datetime.now

import datetime
import mox

m = mox.Mox()

# Stub out the datatime.datetime class.
m.StubOutWithMock(datetime, 'datetime')

# Record a call to 'now', and have it return the value '1234'
datetime.datetime.now().AndReturn(1234)

# Set the mocks to replay mode
m.ReplayAll()
  
# This will return '1234'
datetime.datetime.now()
  
# Verify the time was actually checked.
m.VerifyAll()

# Return datetime.datetime to its default (non-mock) state.
m.UnsetStubs()

Alternatively, rewrite your code so that you can mock out datetime.now without Mox:

def FunctionBeingTested(now=datetime.datetime.now):
  DoSomethingWith(now())

# in test code
def MyNow(): return 1234
FunctionBeingTested(now=MyNow)

Comment by trung%ph...@gtempaccount.com, Dec 31, 2009

is it possible to stub a constructor?

I couldn't do this: self.mox.StubOutWithMock?(ClassToMock?, 'init')

Comment by LeLu...@gmail.com, Feb 6, 2010

@tr.. hmm .. formatting probably removed your underscores in "__init__". I was able to do it with this same kind of call. I'm using pymox version 0.5.1. don't forget to record a call to it before putting your object in replay mode:

    mox_factory.StubOutWithMock(ClassType, "__init__")

    TomboyCommunicator.__init__().AndReturn( None )

    mox_factory.ReplayAll()

Here's a technique I am using to keep perfect control over what methods of an object get called or not during a test:

class TestSomething(unittest.TestCase):
    def setUp(self):
        self.m = mox.Mox()

    def tearDown(self):
        self.m.UnsetStubs()
        self.m.ResetAll()

    def wrap_subject(self, cls, subject_name):
        mock = self.m.CreateMock(cls)

        func = getattr(cls, subject_name)
        wrapper = lambda *x, **y: func(mock, *x, **y)
        setattr(mock, subject_name, wrapper)

        return mock

    def test_a_method_in_an_object(self):
        obj = self.wrap_subject(ObjectContainingMethod, "tested_method")

        # Record calls that should be made in tested_method

        self.m.ReplayAll()

        self.AssertEqual(
            "dummy result. change string to whatever needed",
            obj.tested_method()
        )

        self.m.VerifyAll()

I haven't found a clean way to do the same thing with functions in a module (not contained in an object). I guess I'll be encapsulating everything in classes to be able to test this way.

Code for this example was taken from my project over at GitHub

Comment by pengyu...@gmail.com, Mar 30, 2012

how to mox time.localtime().tm_sec?

Comment by pengyu...@gmail.com, Mar 31, 2012

my code:

.... t = time.gmtime(time.mktime((2012, 10, 1, 15, 26,0,0,0,0))) self.mox.StubOutWithMock?(time, 'localtime') time.localtime().AndReturn?(t) self.mox.ReplayAll?()

58 print "mox localtime:", time.localtime()

othermoudle.func() # call time.localtime() in func() ...

on the line 58,I got a correct mox time: (Pdb) time.localtime() time.struct_time(tm_year=2012, tm_mon=10, tm_mday=1, tm_hour=7, tm_min=26, tm_sec=0, tm_wday=0, tm_yday=275, tm_isdst=0)

and then call time.localtime in an other moudle, I got an error: (Pdb) time.time() 1333178201.334844 (Pdb) time.localtime() UnexpectedMethodCallError?: Unexpected method call Stub for <built-in function localtime>.call() -> None (Pdb)

Can u give me some tips why I got the error? thank u.

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