diff -u b/core/modules/ckeditor/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php b/core/modules/ckeditor/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php
--- b/core/modules/ckeditor/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php
+++ b/core/modules/ckeditor/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php
@@ -84,42 +84,26 @@
    */
   public function testFragmentLink() {
     $session = $this->getSession();
+    $web_assert = $this->assertSession();
+    $ckeditor_id = '#cke_edit-body-0-value';
 
     $this->drupalGet('node/add/page');
 
-    $this->getSession()->getPage();
+    $session->getPage();
 
     // Add a bottom margin to the title field to be sure the body field is not
     // visible. PhantomJS runs with a resolution of 1024x768px.
     $session->executeScript("document.getElementById('edit-title-0-value').style.marginBottom = '800px';");
 
-    // Javascript to test if top of the CKEditor-enabled body field is visible
-    // in the viewport. The NodeElement::isVisible() method doesn't take the
-    // viewport into account.
-    $visibility_check_javascript = <<<JS
-    (function(){
-        var w = window,
-        d = document,
-        e = d.documentElement,
-        el = d.getElementById('cke_edit-body-0-value'),
-        r = el.getBoundingClientRect();
-
-        return (
-          r.top >= 0 &&
-          r.top < (w.innerHeight || e.clientHeight)
-        );
-    }());
-JS;
-
     // Check that the CKEditor-enabled body field is currently not visible in
     // the viewport.
-    $this->assertFalse($session->evaluateScript($visibility_check_javascript), 'CKEditor-enabled body field is not visible.');
+    $web_assert->assertNotVisibleInViewport('css', $ckeditor_id, 'topLeft', 'CKEditor-enabled body field is visible.');
 
     // Trigger a hash change with as target the hidden textarea.
     $session->executeScript("document.location.hash = '#edit-body-0-value';");
 
     // Check that the CKEditor-enabled body field is visible in the viewport.
-    $this->assertTrue($session->evaluateScript($visibility_check_javascript), 'CKEditor-enabled body field is visible.');
+    $web_assert->assertVisibleInViewport('css', $ckeditor_id, 'topLeft', 'CKEditor-enabled body field is not visible.');
   }
 
 }
only in patch2:
unchanged:
--- a/core/tests/Drupal/FunctionalJavascriptTests/JSWebAssert.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/JSWebAssert.php
@@ -2,6 +2,10 @@
 
 namespace Drupal\FunctionalJavascriptTests;
 
+use Behat\Mink\Element\NodeElement;
+use Behat\Mink\Exception\ElementHtmlException;
+use Behat\Mink\Exception\ElementNotFoundException;
+use Behat\Mink\Exception\UnsupportedDriverActionException;
 use Drupal\Tests\WebAssert;
 
 /**
@@ -28,4 +32,201 @@ public function assertWaitOnAjaxRequest($timeout = 10000, $message = 'Unable to
     }
   }
 
+  /**
+   * Test that a node, or it's specific corner, is visible in the viewport.
+   *
+   * Note: Always set the viewport size. This can be done with a PhantomJS
+   * startup parameter or in your test with \Behat\Mink\Session->resizeWindow().
+   * Drupal CI Javascript tests by default use a viewport of 1024x768px.
+   *
+   * @param string $selector_type
+   *   The element selector type (css, xpath).
+   * @param string|array $selector
+   *   The element selector. Note: the first found element is used.
+   * @param bool|string $corner
+   *   (Optional) The corner to test:
+   *   topLeft, topRight, bottomRight, bottomLeft.
+   *   Or FALSE to check the complete element (default behavior).
+   * @param string $message
+   *   (optional) A message for the exception.
+   *
+   * @throws \Behat\Mink\Exception\ElementHtmlException
+   *   When the element doesn't exist.
+   * @throws \Behat\Mink\Exception\ElementNotFoundException
+   *   When the element is not visible in the viewport.
+   */
+  public function assertVisibleInViewport($selector_type, $selector, $corner = FALSE, $message = 'Element is not visible in the viewport.') {
+    $node = $this->session->getPage()->find($selector_type, $selector);
+    if ($node === NULL) {
+      if (is_array($selector)) {
+        $selector = implode(' ', $selector);
+      }
+      throw new ElementNotFoundException($this->session->getDriver(), 'element', $selector_type, $selector);
+    }
+
+    // Check if the node is visible on the page, which is a perquisite of being
+    // visible in the viewport.
+    if (!$node->isVisible()) {
+      throw new ElementHtmlException($message, $this->session->getDriver(), $node);
+    }
+
+    $result = $this->checkNodeVisibilityInViewport($node, $corner);
+
+    if (!$result) {
+      throw new ElementHtmlException($message, $this->session->getDriver(), $node);
+    }
+  }
+
+  /**
+   * Test that a node, or it's specific corner, is not visible in the viewport.
+   *
+   * Note: the node should exist in the page, otherwise this assertion fails.
+   *
+   * @param string $selector_type
+   *   The element selector type (css, xpath).
+   * @param string|array $selector
+   *   The element selector. Note: the first found element is used.
+   * @param bool|string $corner
+   *   (Optional) The corner to test:
+   *   topLeft, topRight, bottomRight, bottomLeft.
+   *   Or FALSE to check the complete element (default behavior).
+   * @param string $message
+   *   (optional) A message for the exception.
+   *
+   * @throws \Behat\Mink\Exception\ElementHtmlException
+   *   When the element doesn't exist.
+   * @throws \Behat\Mink\Exception\ElementNotFoundException
+   *   When the element is not visible in the viewport.
+   *
+   * @see \Drupal\FunctionalJavascriptTests\JSWebAssert::assertVisibleInViewport()
+   */
+  public function assertNotVisibleInViewport($selector_type, $selector, $corner = FALSE, $message = 'Element is visible in the viewport.') {
+    $node = $this->session->getPage()->find($selector_type, $selector);
+    if ($node === NULL) {
+      if (is_array($selector)) {
+        $selector = implode(' ', $selector);
+      }
+      throw new ElementNotFoundException($this->session->getDriver(), 'element', $selector_type, $selector);
+    }
+
+    $result = $this->checkNodeVisibilityInViewport($node, $corner);
+
+    if ($result) {
+      throw new ElementHtmlException($message, $this->session->getDriver(), $node);
+    }
+  }
+
+  /**
+   * Check the visibility of a node, or it's specific corner.
+   *
+   * @param \Behat\Mink\Element\NodeElement $node
+   *   A valid node.
+   * @param bool|string $corner
+   *   (Optional) The corner to test:
+   *   topLeft, topRight, bottomRight, bottomLeft.
+   *   Or FALSE to check the complete element (default behavior).
+   *
+   * @return bool
+   *   Returns TRUE if the node is visible in the viewport, FALSE otherwise.
+   *
+   * @throws \Behat\Mink\Exception\UnsupportedDriverActionException
+   *   When an invalid corner specification is given.
+   */
+  private function checkNodeVisibilityInViewport(NodeElement $node, $corner = FALSE) {
+    $xpath = $node->getXpath();
+
+    // Build the Javascript to test if the complete element or a specific corner
+    // is in the viewport.
+    switch ($corner) {
+      case 'topLeft':
+        $test_javascript_function = <<<JS
+          function t(r, lx, ly) {
+            return (
+              r.top >= 0 &&
+              r.top <= ly &&
+              r.left >= 0 &&
+              r.left <= lx
+            )
+          }
+JS;
+        break;
+
+      case 'topRight':
+        $test_javascript_function = <<<JS
+          function t(r, lx, ly) {
+            return (
+              r.top >= 0 &&
+              r.top <= ly &&
+              r.right >= 0 &&
+              r.right <= lx
+            );
+          }
+JS;
+        break;
+
+      case 'bottomRight':
+        $test_javascript_function = <<<JS
+          function t(r, lx, ly) {
+            return (
+              r.bottom >= 0 &&
+              r.bottom <= ly &&
+              r.right >= 0 &&
+              r.right <= lx
+            );
+          }
+JS;
+        break;
+
+      case 'bottomLeft':
+        $test_javascript_function = <<<JS
+          function t(r, lx, ly) {
+            return (
+              r.bottom >= 0 &&
+              r.bottom <= ly &&
+              r.left >= 0 &&
+              r.left <= lx
+            );
+          }
+JS;
+        break;
+
+      case FALSE:
+        $test_javascript_function = <<<JS
+          function t(r, lx, ly) {
+            return (
+              r.top >= 0 &&
+              r.left >= 0 &&
+              r.bottom <= ly &&
+              r.right <= lx
+            );
+          }
+JS;
+        break;
+
+      // Throw an exception if an invalid corner parameter is given.
+      default:
+        throw new UnsupportedDriverActionException($corner, $this->session->getDriver());
+    }
+
+    // Build the full Javascript test. The shared logic gets the corner
+    // specific test logic injected.
+    $full_javascript_visibility_test = <<<JS
+      (function(t){
+        var w = window,
+        d = document,
+        e = d.documentElement,
+        n = d.evaluate("$xpath", d, null, XPathResult.FIRST_ORDERED_NODE_TYPE, null).singleNodeValue,
+        r = n.getBoundingClientRect(),
+        lx = (w.innerWidth || e.clientWidth),
+        ly = (w.innerHeight || e.clientHeight);
+        
+        return t(r, lx, ly);
+      }($test_javascript_function));
+JS;
+
+    // Check the visibility by injecting and executing the full Javascript test
+    // script in the page.
+    return $this->session->evaluateScript($full_javascript_visibility_test);
+  }
+
 }