Use PHPUnit 9 in PHP 8

Author: javiereguiluz

.github/workflows/ci.yaml

@@ -59,9 +59,14 @@ jobs:
             - if: matrix.php-version == '8.0'
               run: composer update --ignore-platform-req=php
 
-            - name: "Install PHPUnit"
+            - if: matrix.php-version != '8.0' 
+              name: "Install PHPUnit"
               run: vendor/bin/simple-phpunit install
 
+            - if: matrix.php-version == '8.0'
+              name: "Install PHPUnit for PHP 8"
+              run: SYMFONY_PHPUNIT_VERSION=9.4 vendor/bin/simple-phpunit install
+
             - name: "PHPUnit version"
               run: vendor/bin/simple-phpunit --version