GitHub Actions上でPHPUnitを並列に動作させて、CI実行時間を1/4にしました

岩下「あ、Aさん！☓☓☓の件について、Pull Requestを作ったのでお手すき時にレビューお願いします！」
A「OKです、手が空いたら見ておきます〜」

〜〜〜1時間後〜〜〜

A「岩下さん、Pull Requestを見ようとしたら、TestがFailしているところがありました、確認してもらえますか？」
岩下「えっ、あっ、はい承知しました！」

jobs:
  dependencies-install:
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v3

      - name: Composer Cache
        id: composer_cache
        uses: actions/cache@v3
        with:
          path: vendor
          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
          restore-keys: |
            ${{ runner.os }}-composer-

      - name: Setup PHP
        uses: shivammathur/setup-php@v2
        with:
          php-version: "8.0"

      - name: Composer Install
        if: steps.composer_cache.outputs.cache-hit != 'true'
        run: |
          composer install -n --prefer-dist

      - name: Npm Cache
        uses: actions/cache@v3
        id: npm_cache
        with:
          path: node_modules
          key: ${{ runner.os }}-node-${{ hashFiles('**/package-lock.json') }}
          restore-keys: |
            ${{ runner.os }}-node-

      - name: npm install
        if: steps.npm_cache.outputs.cache-hit != 'true'
        run: |
          npm ci

test:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        parallel: [5]
        id: [0, 1, 2, 3, 4]

    steps:
      - uses: actions/checkout@v3

      - name: Use Composer Cache
        uses: actions/cache@v3
        with:
          path: vendor
          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
          restore-keys: |
            ${{ runner.os }}-composer-
      - name: Use Npm Cache
        uses: actions/cache@v3
        with:
          path: node_modules
          key: ${{ runner.os }}-node-${{ hashFiles('**/package-lock.json') }}
          restore-keys: |
            ${{ runner.os }}-node-

      - name: Setup PHP
        uses: shivammathur/setup-php@v2
        with:
          php-version: "8.0"
          extensions: bcmath zip exif mongodb imagick sqlite3

      - name: Run Tests
        run: |
          # NR % 5 == ${{ matrix.id }}の５は並行して実行されるインスタンス数
          find tests/ -name '*Test.php' | sort | awk "NR % 5 == ${{ matrix.id }}" | \\
            xargs php artisan dev:xml:generate-phpunit
          ./vendor/bin/phpunit \\
            --verbose \\
            --configuration phpunit-partial.xml

public function handle()
    {
        $files = $this->argument('files');

        $basePath = base_path();

        $originalXmlFilePath = $basePath . '/phpunit.xml';

        $xml = new \\DOMDocument();

        $xml->load($originalXmlFilePath);

        $testsuite = $xml->createElement('testsuite');
        $testsuite->setAttribute('name', 'partial');

        foreach ($files as $file) {
            $testsuite->appendChild($xml->createElement('file', $file));
        }

        $newTestSuites = $xml->createElement('testsuites');
        $newTestSuites->appendChild($testsuite);

        $phpunit = $xml->getElementsByTagName('phpunit')->item(0);

        $currentTestSuites = $phpunit->getElementsByTagName('testsuites')->item(0);

        $phpunit->replaceChild($newTestSuites, $currentTestSuites);

        $newXmlFilePath = $basePath . '/' . self::XML_FILENAME;

        $xml->save($newXmlFilePath);
    }

test:
    runs-on: ubuntu-latest
    needs: dependencies-install <- 追記
    strategy:
      matrix:
        parallel: [5]
        id: [0, 1, 2, 3, 4]