I have 1 file which loads a particular resource ( from a file ) that takes a while to load.

I have a function in another file which uses that resource by importing it first. When that resource is first imported, it loads and takes a bit.

However, when I’m testing that function that requires that resource, I wanna pass it another smaller resource.

Unfortunately, there aren’t any major refactors I’m able to do to either file1.py or file2.py. Is there a solution using pytest? I haven’t been able to get it working.

file1.py

def load_resource():
    print("Loading big resource...")
    return {"key": "big resource"}

resource = load_resource()

file2.py

from file1 import resource

def my_func():
    return resource["key"]

test.py

import pytest

@pytest.fixture(autouse=True)
def mock_load_resource(monkeypatch):
    def mock_resource():
        return {'key': 'mocked_value'}
    monkeypatch.setattr('file1', 'load_resource', mock_resource)
    monkeypatch.setattr('file1', 'resource', mock_resource())

def test_my_function():
    from file2 import my_func
    result = my_func()
    assert result == 'mocked_value'