Let's say I have a class like this.

class SomeProductionProcess(CustomCachedSingleTon):@classmethoddef loaddata(cls):"""Uses an iterator over a large file in Production for the Data pipeline."""pass

Now at test time I want to change the logic inside the loaddata() method. It would be a simple custom logic that doesn't process large data.

How do we supply custom implementation of loaddata() at testtime using Python Mock UnitTest framework?

Here is a simple way to do it using mock

import mockdef new_loaddata(cls, *args, **kwargs):# Your custom testing overridereturn 1def 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.