Excluding code from coverage in PyTest

Introduction

Sometimes, you want to ignore parts of your code when checking test coverage. This helps focus on important code and avoid false alarms.

When you have debug or logging code that does not affect program logic.

When you include code that runs only on specific platforms or environments.

When you have code that is hard to test or not worth testing, like error handlers for impossible cases.

When you want to exclude generated code or third-party code from coverage reports.

Syntax

PyTest

# Use comment # pragma: no cover after the line you want to exclude
some_code()  # pragma: no cover

The comment # pragma: no cover tells coverage tools to ignore that line.

This works well with pytest and coverage.py tools.

Examples

This line will not be counted in coverage reports.

PyTest

def example():
    print("This runs")  # pragma: no cover

Exclude code that runs only when the script is executed directly.

PyTest

if __name__ == '__main__':  # pragma: no cover
    main()

Exclude debug code from coverage.

PyTest

def debug():
    # This function is for debugging only
    print("Debug info")  # pragma: no cover

Sample Program

This example shows a simple function add tested by test_add. The debug_log function is excluded from coverage using # pragma: no cover.

PyTest

def add(a, b):
    return a + b

def debug_log():
    print("Debug info")  # pragma: no cover


def test_add():
    assert add(2, 3) == 5

# Run tests with coverage: pytest --cov=.
# The debug_log function line is excluded from coverage report.

Important Notes

Use # pragma: no cover only on lines you really want to exclude.

Coverage tools ignore these lines when calculating coverage percentage.

Remember to run coverage with pytest using --cov option.

Summary

Use # pragma: no cover comment to exclude code lines from coverage.

This helps keep coverage reports focused and accurate.

Works well with pytest and coverage.py tools.