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Pytest plugin for excluding tests based on coverage data

Project description

Coverage-based test exclusion plugin for pytest. By looking at which lines are executed by each test, the next test run can be sped up by not executing the tests where no source files have changed.

If you have a large test suite which you often re-run, this plugin can drastically improve the iteration times.


Install with pip:

$ pip install pytest-cov-exclude

pytest-cov-exclude requires Pytest 2.8 or later. It is compatible with Python 2.7, 3.3, 3.4, 3.5, as well as PyPy. It does not work on PyPy 3 due to an unknown bug with the coverage data generated.


The first time you run your test suite, per-test coverage is enabled and the suite will take a little bit longer than usual:

$ py.test

==================== test session starts =====================

# Test output...

================ MANY passed in MANY seconds =================

Now when you re-run the test suite, all tests should have been excluded:

$ py.test

==================== test session starts =====================

# Test output...

=============== MANY deselected in FEW seconds ===============

If a test fails, it will re-run even if nothing changed in order to preserve the general failure status of the test suite.

Forcing individual test inclusion

If you have tests that depend on files not included in coverage data, such as data files or generated sources, you can mark the tests with external_dependencies. This forces them to be re-run even if no files were changed:

def test_something():
    # Run tests from external data files

Known bugs

  • Changes to files during pytest’s collection phase will be ignored. Test files and their dependencies are scanned as soon as possible after the test collection is complete.

    There is a test case marked xfail that highlights this issue.

Running the whole test suite

If you want to force a complete re-run of the whole test suite, you have two options: either disable the plugin, or clear pytest’s cache:

$ py.test -p no:cov-exclude  # Disable the plugin

$ py.test --cache-clear  # Clear pytest's cache


As stated earlier, this plugin requires Pytest 2.8 or later since it depends on the new cache module.

While PyPy is supported, the ujson library used for faster serialization/deserialization is not available, so a fallback to the default JSON implementation is used instead. Because of this, the tests might actually run slower with this plugin under PyPy.

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