Fix json schema validation

src/Json/Json.php

@@ -13,6 +13,11 @@ public function __construct($content)
         $this->content = $this->decode((string) $content);
     }
 
+    public function getContent()
+    {
+        return $this->content;
+    }
+
     public function read($expression, PropertyAccessor $accessor)
     {
         if (is_array($this->content)) {

src/Json/JsonSchema.php

@@ -28,7 +28,7 @@ public function resolve(RefResolver $resolver)
 
     public function validate(Json $json, Validator $validator)
     {
-        $validator->check($json, $this);
+        $validator->check($json->getContent(), $this->getContent());
 
         if (!$validator->isValid()) {
             $msg = "JSON does not validate. Violations:".PHP_EOL;

tests/units/Json/JsonSchema.php

@@ -60,7 +60,7 @@ public function test_should_validate_correct_json()
             )
                 ->mock($validator)
                     ->call('check')
-                    ->withArguments($json, $schema)
+                    ->withArguments($json->getContent(), $schema->getContent())
                     ->once()
 
                 ->boolean($result)