fix PHP 8.1 implicit conversion deprecation

upgraded dev to php unit 9

composer.json

@@ -27,7 +27,7 @@
     }
   },
   "require-dev": {
-    "phpunit/phpunit": "^8.5 | ^9.5",
+    "phpunit/phpunit": "^9.5",
     "guzzlehttp/guzzle": "^7.4",
     "http-interop/http-factory-guzzle": "^1.2"
   }

phpunit.xml

@@ -1,22 +1,23 @@
 <?xml version="1.0" encoding="UTF-8"?>
-
-<phpunit backupGlobals="false"
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         backupGlobals="false"
          backupStaticAttributes="false"
          bootstrap="vendor/autoload.php"
          colors="true"
          convertErrorsToExceptions="true"
          convertNoticesToExceptions="true"
          convertWarningsToExceptions="true"
          processIsolation="false"
-         stopOnFailure="false">
+         stopOnFailure="false"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/9.3/phpunit.xsd">
+    <coverage>
+        <include>
+            <directory>src/</directory>
+        </include>
+    </coverage>
     <testsuites>
         <testsuite name="Test Suite">
             <directory>tests/</directory>
         </testsuite>
     </testsuites>
-    <filter>
-        <whitelist>
-            <directory>src/</directory>
-        </whitelist>
-    </filter>
-</phpunit>
+</phpunit>

src/Middleware/RateLimitMiddleware.php

@@ -82,7 +82,7 @@ public function process(RequestInterface $request, RequestHandlerInterface $hand
 
     private function getCounter(): Counter
     {
-        $default = new Counter(new DateTime(date('Y-m-d H:i:s.u', microtime(true) + $this->duration)));
+        $default = new Counter(DateTime::createFromFormat('U', $this->duration + time()));
 
         /** @var Counter $counter */
         $counter = $this->cache->get($this->cacheKey, $default);