Detect CI via environment variable

CI systems typically set the environment variable CI as a de facto standard for easy CI detection. Here are details of several popular CI services:

In general, across programming languages, test frameworks allow behavior changes based on the environment variables set by the CI system.

Python Pytest

Pytest handles conditional tests well. This allows skipping a subset of tests on CI by detecting the CI environment variable:

import os
import pytest

CI = os.environ.get('CI') in ('True', 'true')

@pytest.mark.skipif(CI, reason="not a test for CI")
def test_myfun():

CMake CTest

CTest can also use CI environment variables to adjust test behavior.

  set(NO_GFX on)

add_test(NAME menu COMMAND menu)
set_tests_properties(menu PROPERTIES DISABLED $<BOOL:${NO_GFX}>)

Always enclose "$ENV{}" in quotes in case the environment variable is empty or not defined, or the configuration step may syntax error.