Support PHPUnit 9

Author: Naktibalda

.travis.yml

@@ -3,6 +3,7 @@ language: php
 php:
   - 7.2
   - 7.3
+  - 7.4
 
 cache:
   directories:
@@ -14,4 +15,4 @@ sudo: false
 before_install:
   - composer update --prefer-source
 
-script: vendor/bin/phpunit tests
+script: vendor/bin/phpunit tests

composer.json

@@ -10,6 +10,6 @@
         }
     },
     "require": {
-        "phpunit/phpunit": "^8.4"
+        "phpunit/phpunit": "^8.4 | ^9.0"
     }
 }