PHP Coverage Filter

• Run only the tests that cover lines that have been changed.
• View the report for only files that have been changed.

Install

Via Phive:

phive install brianhenryie/php-diff-test

composer require --dev brianhenryie/php-diff-test

Run

Requires XDEBUG_MODE=coverage.

difftest filter

Prints a filter to use with PHPUnit or Codeception, so you only run tests relevant to changes in the branch you're working on.

• Run: phpunit --filter="$(difftest filter)" or codecept run suitename "$(difftest filter)".
• Try just difftest filter to see the filter that will be applied, which is effectively difftest filter --input-files <glob *.cov> --diff-from main --diff-to HEAD~0 --granularity line
• Try difftest filter --diff-from HEAD~3 to print a shallower filter
• Try difftest filter --granularity file to print a filter which includes all tests that cover any line in changed files (this makes the HTML report make more sense)

difftest coverage

Outputs a new .cov file containing only the files whose lines have been changed in the diff. Intended to then print a HTML coverage report

• Run: difftest coverage --input-files "php-coverage1.cov,php-coverage2.cov" --diff-from main --diff-to HEAD~0 --output-file diff-coverage/diff-from-to.cov
• Then to generate the new HTML report: phpcov merge ./diff-coverage --html ./diff-coverage/report. NB phpcov will merge all .cov files in the directory and subdirectories so you should set difftest coverage's new .cov --output-file to be in its own directory.

How it works

Runs git diff, parses which lines have been changed, parses *.cov codecoverage files to match which tests cover those lines.

The script looks in the current working directory, its tests subfolder, and each of the tests immediate subfolders for *.cov.

It also checks tests for Codeception *.suite.y*ml files, and assumes a file named unit.cov corresponds with unit.suite.yml to determine should the output be formatted for codecept run... syntax rather than PHPUnit --filter="..." syntax.

Obviously, it's assumed you're working inside a Git repo and have previously generated code coverage (in PHP .cov format).

⚠️ This has been tested to just over 500 test cases. It will inevitably have its limits, when you should probably use groups to first generate the coverage to be filtered.

TODO

• I think the diff doesn't track unstaged/uncommitted files which could have code coverage
• Also run tests changed in the diff / run all tests changed since the code coverage was generated (i.e. Tests written after the code coverage report are not included in the filter)
• Figure how best merge/increment coverage reports – i.e. once difftest coverage has been run on the full coverage report, add to it when new tests are written
• Allow specifying a hash to diff with – i.e. make pull requests run faster
• sebastianbergmann/php-code-coverage#571 – code coverage annotations make this tool less thorough
• Tidy up the code – I'm not sure is the diff report's lines the current lines or the before lines... use both for best effect
• Tests!
• Should this be implemented as a PHPUnit extension?

See Also

• https://github.com/robiningelbrecht/phpunit-coverage-tools
• https://docs.phpunit.de/en/10.5/extending-phpunit.html
• https://localheinz.com/articles/2023/02/14/extending-phpunit-with-its-new-event-system/