断言在Python单元测试中调用了一个方法

Question

假设我在Python单元测试中有以下代码:

aw = aps.Request("nv1")
aw2 = aps.Request("nv2", aw)

是否有一种简单的方法可以断言aw.Clear()在测试的第二行中调用了一个特定的方法(在我的例子中)？例如,有这样的事情:

#pseudocode:
assertMethodIsCalled(aw.Clear, lambda: aps.Request("nv2", aw))

Answer 1

我使用Mock(现在是py3.3 +上的unittest.mock):

from mock import patch
from PyQt4 import Qt


@patch.object(Qt.QMessageBox, 'aboutQt')
def testShowAboutQt(self, mock):
    self.win.actionAboutQt.trigger()
    self.assertTrue(mock.called)

对于您的情况,它可能看起来像这样:

import mock
from mock import patch


def testClearWasCalled(self):
   aw = aps.Request("nv1")
   with patch.object(aw, 'Clear') as mock:
       aw2 = aps.Request("nv2", aw)

   mock.assert_called_with(42) # or mock.assert_called_once_with(42)

Mock支持许多有用的功能,包括修补对象或模块的方法,以及检查正确的东西是否被调用等等.

买者自负!(买家要小心!)

如果您错误输入assert_called_with(assert_called_once或assert_called_wiht),您的测试可能仍会运行,因为Mock会认为这是一个模拟功能,并且很乐意继续使用,除非您使用autospec=true.有关更多信息,请阅读assert_called_once:威胁或威胁.

Answer 2

是的,如果您使用的是Python 3.3+.您可以使用内置的unittest.mockassert方法调用.对于Python 2.6+,使用滚动backport Mock,这是相同的事情.

以下是您案例中的一个简单示例:

from unittest.mock import MagicMock
aw = aps.Request("nv1")
aw.Clear = MagicMock()
aw2 = aps.Request("nv2", aw)
assert aw.Clear.called

Answer 3

我不知道任何内置的东西.实现起来非常简单:

class assertMethodIsCalled(object):
    def __init__(self, obj, method):
        self.obj = obj
        self.method = method

    def called(self, *args, **kwargs):
        self.method_called = True
        self.orig_method(*args, **kwargs)

    def __enter__(self):
        self.orig_method = getattr(self.obj, self.method)
        setattr(self.obj, self.method, self.called)
        self.method_called = False

    def __exit__(self, exc_type, exc_value, traceback):
        assert getattr(self.obj, self.method) == self.called,
            "method %s was modified during assertMethodIsCalled" % self.method

        setattr(self.obj, self.method, self.orig_method)

        # If an exception was thrown within the block, we've already failed.
        if traceback is None:
            assert self.method_called,
                "method %s of %s was not called" % (self.method, self.obj)

class test(object):
    def a(self):
        print "test"
    def b(self):
        self.a()

obj = test()
with assertMethodIsCalled(obj, "a"):
    obj.b()

这要求对象本身不会修改self.b,这几乎总是正确的.

Answer 4

是的,我可以给你大纲,但我的Python有点生疏,我太忙了,无法详细解释.

基本上,您需要在调用原始方法的方法中放置代理,例如:

 class fred(object):
   def blog(self):
     print "We Blog"


 class methCallLogger(object):
   def __init__(self, meth):
     self.meth = meth

   def __call__(self, code=None):
     self.meth()
     # would also log the fact that it invoked the method

 #example
 f = fred()
 f.blog = methCallLogger(f.blog)

这个关于可调用的StackOverflow答案可以帮助您理解上述内容.

更详细:

虽然答案被接受,但由于与格伦进行了有趣的讨论并且有几分钟免费,我想扩大我的答案:

# helper class defined elsewhere
class methCallLogger(object):
   def __init__(self, meth):
     self.meth = meth
     self.was_called = False

   def __call__(self, code=None):
     self.meth()
     self.was_called = True

#example
class fred(object):
   def blog(self):
     print "We Blog"

f = fred()
g = fred()
f.blog = methCallLogger(f.blog)
g.blog = methCallLogger(g.blog)
f.blog()
assert(f.blog.was_called)
assert(not g.blog.was_called)

Answer 5

您可以手动或使用pymoxaw.Clear等测试框架进行模拟。手动地，你可以使用类似这样的东西来完成它：

class MyTest(TestCase):
  def testClear():
    old_clear = aw.Clear
    clear_calls = 0
    aw.Clear = lambda: clear_calls += 1
    aps.Request('nv2', aw)
    assert clear_calls == 1
    aw.Clear = old_clear

使用 pymox，你可以这样做：

class MyTest(mox.MoxTestBase):
  def testClear():
    aw = self.m.CreateMock(aps.Request)
    aw.Clear()
    self.mox.ReplayAll()
    aps.Request('nv2', aw)