add docblock for assertJsonByKeys

Author: Treggats

src/Tempest/Framework/Testing/Http/TestResponseHelper.php

@@ -230,6 +230,15 @@ public function assertJson(array $expected): self
         return $this;
     }
 
+    /**
+     * This assertion lets you assert that the response contains the given keys and values.
+     * The first array is the expected values, the second array is the keys to check.
+     *
+     * @param array<string, mixed> $expected The expected values.
+     * @param array<string> $keys The keys to check.
+     *
+     * @example assertJsonByKeys(['id' => 1, 'title' => 'The Odyssee'], keys: ['id', 'title'])
+     */
     public function assertJsonByKeys(array $expected, array $keys): self
     {
         $filteredBody = array_reduce(