chore: add phpunit version to CI matrix

Author: delatrie

.github/workflows/build.yml

@@ -11,7 +11,7 @@ on:
 
 jobs:
   tests:
-    name: PHP ${{ matrix.php-version }} on ${{ matrix.os }} (${{ matrix.prefer-lowest }})
+    name: PHP ${{ matrix.php-version }} PHPUnit ${{matrix.phpunit-version}} on ${{ matrix.os }} (${{ matrix.prefer-lowest }})
     runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false
@@ -25,15 +25,29 @@ jobs:
           - ubuntu-latest
           - windows-latest
           - macOS-latest
+        phpunit-version:
+          - "10"
+          - "11"
+          - "12"
         prefer-lowest:
           - ""
           - "--prefer-lowest"
         include:
           # PHPUnit ^10.5.32 is incompatible with paratest 7.3.
           # Paratest 7.4.6, which fixes the incompatibility, requires PHP 8.2
           - php-version: "8.1"
-            prefer-lowest: ""
+            phpunit-version: "10"
             update-constraints: "--with=phpunit/phpunit:<10.5.32"
+        exclude:
+          # PHPUnit ^11 requires PHP 8.2
+          - phpunit-version: "11"
+            php-version: "8.1"
+
+          # PHPUnit ^12 requires PHP 8.3
+          - phpunit-version: "12"
+            php-version: "8.1"
+          - phpunit-version: "12"
+            php-version: "8.2"
     steps:
       - name: Checkout
         uses: actions/checkout@v4