minor #97 Inline $tmpDir (derrabus)

This PR was merged into the 2.1-dev branch.

Discussion
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Inline $tmpDir

This PR fixes an issue where the variable `$tmpDir` of `CovertTest` is used in a data provider before it is initialized through the `setUp()` method. Inlining the variable avoids this trap and makes the whole code a bit clearer.

I spotted this while running the tests with PHP 8.1 where passing `null` to `tempnam()` triggers a deprecation warning.

Commits
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d152649 Inline $tmpDir

Author: derrabus

Tests/Functional/CovertTest.php

@@ -34,15 +34,11 @@
  */
 class CovertTest extends TestCase
 {
-    private $tmpDir;
-
     protected function setUp(): void
     {
         if (!class_exists(Psr7Request::class)) {
             $this->markTestSkipped('nyholm/psr7 is not installed.');
         }
-
-        $this->tmpDir = sys_get_temp_dir();
     }
 
     /**
@@ -233,7 +229,7 @@ public function responseProvider()
 
     private function createUploadedFile($content, $originalName, $mimeType, $error)
     {
-        $path = tempnam($this->tmpDir, uniqid());
+        $path = tempnam(sys_get_temp_dir(), uniqid());
         file_put_contents($path, $content);
 
         return new UploadedFile($path, $originalName, $mimeType, $error, true);