fix mixed return type with PHP 7.4

Author: Art4

tests/Unit/Input/RequestStringInputTest.php

@@ -26,8 +26,10 @@ public function testGetAsObjectFromStringReturnsObject(): void
 
     /**
      * @dataProvider jsonValuesProviderWithoutString
+     *
+     * @param mixed $input
      */
-    public function testCreateWithoutStringThrowsException(mixed $input): void
+    public function testCreateWithoutStringThrowsException($input): void
     {
         $this->expectException(InputException::class);
         $this->expectExceptionMessage(

tests/Unit/Input/ResponseStringInputTest.php

@@ -26,8 +26,10 @@ public function testGetAsObjectFromStringReturnsObject(): void
 
     /**
      * @dataProvider jsonValuesProviderWithoutString
+     *
+     * @param mixed $input
      */
-    public function testCreateWithoutStringThrowsException(mixed $input): void
+    public function testCreateWithoutStringThrowsException($input): void
     {
         $this->expectException(InputException::class);
         $this->expectExceptionMessage(