Speed up tests with parallel execution

Author: maennchen

.github/CONTRIBUTING.md

@@ -117,6 +117,8 @@ $ composer run install:tools # Install phpDocumentor using phive
 After following the steps shown above, ZipStream-PHP's test suite is run like
 this:
 
+Make sure `xdebug` is installed for test coverage.
+
 ```bash
 $ composer run test:unit
 ```

.github/workflows/part_test.yml

@@ -73,9 +73,7 @@ jobs:
         if: matrix.php == 'nightly'
         run: composer install --prefer-dist --ignore-platform-req=php+
       - name: Run PHPUnit
-        run: composer run test:unit
-        env:
-          XDEBUG_MODE: coverage
+        run: composer run test:unit:cov
       - name: Upload coverage results to Coveralls
         env:
           COVERALLS_REPO_TOKEN: ${{ secrets.GITHUB_TOKEN }}

composer.json

@@ -33,7 +33,8 @@
     "mikey179/vfsstream": "^1.6",
     "php-coveralls/php-coveralls": "^2.5",
     "friendsofphp/php-cs-fixer": "^3.16",
-    "vimeo/psalm": "^6.0"
+    "vimeo/psalm": "^6.0",
+    "brianium/paratest": "^7.7"
   },
   "suggest": {
     "psr/http-message": "^2.0",
@@ -46,9 +47,12 @@
       "@test:formatted",
       "@test:lint"
     ],
-    "test:unit": "phpunit --coverage-clover=coverage.clover.xml --coverage-html cov",
+    "test:unit": "paratest --functional",
+    "test:unit:cov": "XDEBUG_MODE=coverage paratest --functional --coverage-clover=coverage.clover.xml --coverage-html cov",
     "test:unit:slow": "@test:unit --group slow",
+    "test:unit:slow:cov": "@test:unit:cov --group slow",
     "test:unit:fast": "@test:unit --exclude-group slow",
+    "test:unit:fast:cov": "@test:unit:cov --exclude-group slow",
     "test:formatted": "@format --dry-run --stop-on-violation --using-cache=no",
     "test:lint": "psalm --stats --show-info=true --find-unused-psalm-suppress",
     "coverage:report": "php-coveralls --coverage_clover=coverage.clover.xml --json_path=coveralls-upload.json --insecure",