Registering markers in pytest.ini - Build an Automation Script

Verify custom pytest markers are registered and used correctly

Preconditions (2)

Step 1: Open pytest.ini file

Step 2: Add a custom marker named 'slow' with description 'marks tests as slow'

Step 3: Create a test file test_sample.py

Step 4: Add two test functions: one marked with @pytest.mark.slow and one without any marker

Step 5: Run pytest with the option '-m slow' to run only tests marked as slow

✅ Expected Result: Only the test function marked with @pytest.mark.slow runs successfully, and pytest does not show any warnings about unregistered markers

Automation Requirements - pytest

Assertions Needed:

Verify that tests marked with 'slow' run when using '-m slow'

Verify no warnings about unregistered markers appear during test run

Best Practices:

Register custom markers in pytest.ini under [pytest] section

Use descriptive marker names and descriptions

Avoid hardcoding markers in test code without registration

Run pytest with '-m' option to filter tests by marker

Automated Solution

PyTest

[pytest]
markers =
    slow: marks tests as slow

# test_sample.py
import pytest

def test_fast():
    assert 1 + 1 == 2

@pytest.mark.slow
def test_slow():
    assert sum([1, 2, 3]) == 6

# Command to run in terminal:
# pytest -m slow

The pytest.ini file registers the custom marker slow under the [pytest] section. This prevents pytest from showing warnings about unregistered markers.

The test file test_sample.py contains two tests: test_fast without any marker and test_slow marked with @pytest.mark.slow.

Running pytest -m slow runs only the tests marked with slow. The assertion verifies the test logic is correct.

This setup ensures marker registration and usage are correct and warnings are avoided.

Common Mistakes - 3 Pitfalls

Not registering custom markers in pytest.ini

Using marker names inconsistently between pytest.ini and test code

{'mistake': "Running pytest without the '-m' option to filter by marker", 'why_bad': 'All tests run, so marker filtering is not tested or used', 'correct_approach': "Use 'pytest -m <marker>' to run only tests with that marker"}

Bonus Challenge

Add two more custom markers 'fast' and 'database' in pytest.ini and create tests using them. Run tests filtered by each marker.

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