Require PHPUnit ^7.0

Author: Slamdunk

composer.json

@@ -17,7 +17,7 @@
         "phpoffice/phpexcel": "^1.8",
         "phpstan/phpstan": "^0.9.1",
         "phpstan/phpstan-phpunit": "^0.9.3",
-        "phpunit/phpunit": "^6.5",
+        "phpunit/phpunit": "^7.0",
         "roave/security-advisories": "dev-master",
         "slam/php-cs-fixer-extensions": "^1.13",
         "slam/php-debug-r": "^1.2",