Python mocking global variable declared in another function

Question

I am unit-testing a function which uses variable declared by other function.

def first_fun():
   global file_path
   file_path = get_file_path()
   .
   .

def second_fun():
   with open(file_path, "r") as flz:
   .
   .

How do I mock file_path while testing second_fun()? I tried this but doesn't work.

   @patch.object(source_module, 'file_path')
   def test_second_fun(self):
          source_module.second_fun()

I keep on getting ... does not have the attribute 'file_path'

Answer 1

Two things to consider:

First:

Explicit is better than implicit

in this case, the file_path should be a function parameter.

Second: for your test to be an unit test, you should patch open(), not a path, because you shouldn't depend on a external ressource.