How can I use global variables through tests?

In my example:

@pytest.fixture
def global_var():
    pytest.global_variable_1 = 100

def test_1(global_var):
	pytest.global_variable_1 +=1
	print(pytest.global_variable_1)

def test_2(global_var):
	pytest.global_variable_1 +=1
	print(pytest.global_variable_1)

def test_3(global_var):
	pytest.global_variable_1 +=1
	print(pytest.global_variable_1)

Global variable pytest.global_variable works only in test_1. output: 101 101 101

What do I wrong in?

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State:
Created 6 years ago
Comments:10 (3 by maintainers)

Top GitHub Comments

8reactions

nicoddemuscommented, Jan 15, 2018

Every time a fixture is requested in a test (def test_1(global_var)) the fixture function will be called and the result will be passed as the parameter value: what’s happening here is that because each test requires the global variable, global_var is being executed each time and resetting the value of pytest.global_variable_1 to 100.

Fixtures are meant to avoid using global variables in the first place, they are meant to provide resources to test functions that are isolated and particular for each test.

You can update your code as follows:

import pytest
pytest.global_variable_1 = 100

def test_1():
	pytest.global_variable_1 +=1
	print(pytest.global_variable_1)

def test_2():
	pytest.global_variable_1 +=1
	print(pytest.global_variable_1)

def test_3():
	pytest.global_variable_1 +=1
	print(pytest.global_variable_1)

This will behave like you expect it to.

Disclaimer: using global variables in general (and in testing in particular) is generally a bad idea™; if you look it up you will find dozens of posts/articles explaining why this is bad in general.

2reactions

RonnyPfannschmidtcommented, Jan 15, 2018

for each function you set it back to 100 in the setup, then increment it by 1

so its doing exactly what you told it to