diff --git a/core/tests/Drupal/Tests/Core/Template/AttributeTest.php b/core/tests/Drupal/Tests/Core/Template/AttributeTest.php
index b04eb51..785d506 100644
--- a/core/tests/Drupal/Tests/Core/Template/AttributeTest.php
+++ b/core/tests/Drupal/Tests/Core/Template/AttributeTest.php
@@ -58,6 +58,67 @@ public function testRemove() {
   }
 
   /**
+   * Test setting an attributes.
+   * @covers ::setAttribute()
+   */
+  public function testSetAttribute() {
+    $attribute = new Attribute();
+
+    // Test empty attribtues are not being set.
+    $attribute->setAttribute('id', NULL);
+    $this->assertEmpty($attribute['class']);
+    $attributes = array('alt', 'id', 'src', 'title', 'value', NULL, FALSE, '');
+    foreach ($attributes as $key) {
+      // Test various permutations of adding values to empty Attribute objects.
+      foreach (array(NULL, FALSE, '') as $value) {
+        // Single value.
+        $attribute->setAttribute($key, $value);
+        $this->assertEmpty((string) $attribute);
+      }
+    }
+
+    // Test adding various attributes.
+    $attributes = array('alt', 'id', 'src', 'title', 'value');
+    foreach ($attributes as $key) {
+      $attribute = new Attribute();
+      $attribute->setAttribute($key, 'kitten');
+      $this->assertEquals('kitten', $attribute[$key]);
+    }
+  }
+
+  /**
+   * Test removing of attributes.
+   */
+  public function testRemoveAttribute() {
+    $attributes = array(
+      'alt' => 'Alternative text',
+      'id' => 'bunny',
+      'src' => 'zebra',
+      'style' => 'color: pink;',
+      'title' => 'lama',
+      'value' => 'ostrich',
+    );
+    $attribute = new Attribute($attributes);
+
+    // Single value.
+    $attribute->removeAttribute('alt');
+    $this->assertEmpty($attribute['alt']);
+
+    // Multiple values.
+    $attribute->removeAttribute('id', 'src');
+    $this->assertEmpty($attribute['id']);
+    $this->assertEmpty($attribute['src']);
+
+    // Single value in array.
+    $attribute->removeAttribute(['style']);
+    $this->assertEmpty($attribute['style']);
+
+    // Multiple values in array.
+    $attribute->removeAttribute(['title', 'value']);
+    $this->assertEmpty((string) $attribute);
+  }
+
+  /**
    * Tests adding class attributes with the AttributeArray helper method.
    * @covers ::addClass()
    */