Make View::$hasRendered protected as add getter method for it.

src/View/View.php

@@ -191,7 +191,7 @@ class View implements EventDispatcherInterface
      *
      * @var bool
      */
-    public $hasRendered = false;
+    protected $hasRendered = false;
 
     /**
      * List of generated DOM UUIDs.
@@ -1394,6 +1394,16 @@ public function loadHelper($name, array $config = [])
         return $this->{$class} = $helpers->load($name, $config);
     }
 
+    /**
+     * Check whether the view has been rendered.
+     *
+     * @return bool
+     */
+    public function hasRendered()
+    {
+        return $this->hasRendered;
+    }
+
     /**
      * Returns filename of given action's template file (.ctp) as a string.
      * CamelCased action names will be under_scored by default.

tests/TestCase/View/ViewTest.php

@@ -2135,6 +2135,19 @@ public function testGetSetLayout()
         $this->assertSame($layout, 'foo');
     }
 
+    /**
+     * Test testHasRendered()
+     *
+     * @return void
+     */
+    public function testHasRendered()
+    {
+        $this->assertFalse($this->View->hasRendered());
+
+        $this->View->render('index');
+        $this->assertTrue($this->View->hasRendered());
+    }
+
     /**
      * Test magic getter and setter for removed properties.
      *