How to supply a mock class method for python unit test?

Here is a simple way to do it using mock

import mock


def new_loaddata(cls, *args, **kwargs):
    # Your custom testing override
    return 1


def test_SomeProductionProcess():
    with mock.patch.object(SomeProductionProcess, 'loaddata', new=new_loaddata):
        obj = SomeProductionProcess()
        obj.loaddata()  # This will call your mock method

I’d recommend using pytest instead of the unittest module if you’re able. It makes your test code a lot cleaner and reduces a lot of the boilerplate you get with unittest.TestCase-style tests.