I installed pytest-mock and using a mocker I am trying to function as patch does, but I get "Type Error: Need a valid target to patch. You supplied 'return a + b'"

# test_capitalize.py
import time
def sum(a, b): time.sleep(10) return a + b
def test_sum(mocker): mocker.patch('return a + b'); assertEqual(sum(2, 3), 9)

1

1 Answer

patch requires a path to the function being patched. You could do something like this:

import pytest
def sum(a, b): return a + b
def test_sum1(mocker): mocker.patch(__name__ + ".sum", return_value=9) assert sum(2, 3) == 9
def test_sum2(mocker): def crazy_sum(a, b): return b + b mocker.patch(__name__ + ".sum", side_effect=crazy_sum) assert sum(2, 3) == 6

Result:

$ pytest -v patch_test.py
============= test session starts ==============
platform cygwin -- Python 3.6.4, pytest-3.10.1, py-1.7.0, pluggy-0.8.0 -- /usr/bin/python3
cachedir: .pytest_cache
rootdir: /home/xyz/temp, inifile:
plugins: mock-1.10.0, cov-2.6.0
collected 2 items
patch_test.py::test_sum1 PASSED [ 50%]
patch_test.py::test_sum2 PASSED [100%]
=========== 2 passed in 0.02 seconds ===========

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