Menu
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)
551
Advanced: Mocking in Unit Test In pytest , mocking can replace the return value of a function within a function. This is useful for testing the desired function and replacing the return value of a nested function within that desired function we are testing.
mock is a library for testing in Python. It allows you to replace parts of your system under test with mock objects and make assertions about how they have been used. unittest. mock provides a core Mock class removing the need to create a host of stubs throughout your test suite.
mock provides a powerful mechanism for mocking objects, called patch() , which looks up an object in a given module and replaces that object with a Mock . Usually, you use patch() as a decorator or a context manager to provide a scope in which you will mock the target object.
Mock is a type, and patch is a context. So you are going to pass or receive Mock instances as parameters, and apply patch contexts to blocks of code. (Lowercase 'mock' is just the name of the package.)
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 ===========
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
