Patch + Parametrize unittest Python

Question

I am trying to parametrize unit tests in Python using parameterize library and unittest framework. I need to patch certain functions and I use the following which works

@parameterized.expand([
    [a1, b1],
    [a2, b2]
])
@patch("package.module.f2")
@patch("package.module.f1")
def test_my_func(self, a, b, f1, f2):
    f1.return_value = "Hello"
    f2.return_value = "World"

However, the order of arguments in this working case is a bit weird. Generally while patching the arguments are passed from bottom to top. But when I use parameterize, along with patch, I had expected something like

@parameterized.expand([
    [a1, b1],
    [a2, b2]
])
@patch("package.module.f2")
@patch("package.module.f1")
def test_my_func(self, f1, f2, a, b):
    f1.return_value = "Hello"
    f2.return_value = "World"

but it doesn't work. Can somebody please explain?

Thanks

score 2 · Answer 1 · answered Aug 09 '22 at 15:14

According to the documentation

Using with @mock.patch

parameterized can be used with mock.patch, but the argument ordering can be confusing. The @mock.patch(...) decorator must come below the @parameterized(...), and the mocked parameters must come last:
@mock.patch("os.getpid")
class TestOS(object):
   @parameterized(...)
   @mock.patch("os.fdopen")
   @mock.patch("os.umask")
   def test_method(self, param1, param2, ..., mock_umask, mock_fdopen, mock_getpid):
       ...
Note: the same holds true when using @parameterized.expand.

considering the documentation, your method parameters are out of order:

@parameterized.expand([
    [a1, b1],
    [a2, b2]
])
@patch("package.module.f2")
@patch("package.module.f1")
def test_my_func(self, a, b, f1, f2):
    f1.return_value = "Hello"
    f2.return_value = "World"

Patch + Parametrize unittest Python

1 Answers1