GH Actions: warm PHPUnit cache on PHPUnit 9.3+

As of PHPUnit 9.3, PHPUnit started using PHP-Parser as a basis to calculate code coverage. PHP Parser also polyfills tokens and that can interfere with the sniffs, but also with the code coverage runs.

PHPUnit has also added a new feature in PHPUnit 9.3.4 to warm the code cache ahead of running tests recording code coverage. Using that feature should prevent the token interference.

Notes regarding cache-warming:
* The `--coverage-cache` and `--warm-coverage-cache` options are available since PHPUnit 9.3.4 and if these are used on older PHPUnit versions, PHPUnit will error out with an "unrecognized CLI argument" error.
* In other words: these options can only be used with PHPUnit 9.3+, which is why the PHPUnit version is checked and remembered and subsequently used in the conditions.
* Also: running PHPUnit with the `--warm-coverage-cache` option _does not run the tests_. It literally only warms the cache, which is why this is implemented as a separate step in the workflow.
* The cache directory can be configured in the `phpunit.xml[.dist]` file, but only when using the PHPUnit 9.3+ `coverage` XML tag.
    As the PHPUnit config used needs to stay cross-version compatible with older PHPUnit versions, the CLI option is used for now.

Refs:
* sebastianbergmann/php-code-coverage#798 (comment)
* sebastianbergmann/phpunit@9.3.3...9.3.4

Author: jrfnl

.github/workflows/test.yml

@@ -234,12 +234,33 @@ jobs:
           # Bust the cache at least once a month - output format: YYYY-MM.
           custom-cache-suffix: $(date -u "+%Y-%m")
 
+      - name: Grab PHPUnit version
+        id: phpunit_version
+        # yamllint disable-line rule:line-length
+        run: echo "VERSION=$(vendor/bin/phpunit --version | grep --only-matching --max-count=1 --extended-regexp '\b[0-9]+\.[0-9]+')" >> $GITHUB_OUTPUT
+
+      - name: "DEBUG: Show grabbed version"
+        run: echo ${{ steps.phpunit_version.outputs.VERSION }}
+
       - name: 'PHPCS: set the path to PHP'
         run: php bin/phpcs --config-set php_path php
 
-      - name: 'PHPUnit: run the tests with code coverage'
+      # PHPUnit 9.3 started using PHP-Parser for code coverage, which can cause issues due to Parser
+      # also polyfilling PHP tokens.
+      # As of PHPUnit 9.3.4, a cache warming option is available.
+      # Using that option prevents issues with PHP-Parser backfilling PHP tokens during our test runs.
+      - name: "Warm the PHPUnit cache (PHPUnit 9.3+)"
+        if: ${{ steps.phpunit_version.outputs.VERSION >= '9.3' }}
+        run: vendor/bin/phpunit --coverage-cache ./build/phpunit-cache --warm-coverage-cache
+
+      - name: "Run the unit tests with code coverage (PHPUnit < 9.3)"
+        if: ${{ steps.phpunit_version.outputs.VERSION < '9.3' }}
         run: vendor/bin/phpunit tests/AllTests.php
 
+      - name: "Run the unit tests with code coverage (PHPUnit 9.3+)"
+        if: ${{ steps.phpunit_version.outputs.VERSION >= '9.3' }}
+        run: vendor/bin/phpunit tests/AllTests.php --coverage-cache ./build/phpunit-cache
+
       - name: Upload coverage results to Coveralls
         if: ${{ success() }}
         uses: coverallsapp/github-action@v2

composer.json

@@ -36,7 +36,7 @@
         "ext-xmlwriter": "*"
     },
     "require-dev": {
-        "phpunit/phpunit": "^4.0 || ^5.0 || ^6.0 || ^7.0 || ^8.0 || ^9.0"
+        "phpunit/phpunit": "^4.0 || ^5.0 || ^6.0 || ^7.0 || ^8.0 || ^9.3.4"
     },
     "bin": [
         "bin/phpcbf",