test php8

Author: okbang9

.github/workflows/test-ci.yml

@@ -34,7 +34,7 @@ jobs:
           composer self-update
           composer install --no-interaction --prefer-source --no-dev
           composer require squizlabs/php_codesniffer=3.6.0
-          composer require phpunit/phpunit=9.0.0
+          composer require --ignore-platform-reqs phpunit/phpunit=9.0.0
 
       - name: Run cases
         run: |