Ensure to have the last version of phpunit in require-dev.

mathieutu · mathieutu · commit bf414e2a53e7 · 2020-04-08T13:04:00.000+02:00
diff --git a/composer.json b/composer.json
@@ -28,6 +28,9 @@
         "symfony/serializer": "^4.0|^5.0",
         "symfony/yaml": "^4.0|^5.0"
     },
+    "require-dev": {
+        "phpunit/phpunit": "^9.1.0"
+    },
     "autoload": {
         "psr-4": {
             "Spatie\\Snapshots\\": "src"
