diff --git a/core/modules/rest/src/Plugin/Derivative/EntityDerivative.php b/core/modules/rest/src/Plugin/Derivative/EntityDerivative.php
index 888a724..4655077 100644
--- a/core/modules/rest/src/Plugin/Derivative/EntityDerivative.php
+++ b/core/modules/rest/src/Plugin/Derivative/EntityDerivative.php
@@ -114,12 +114,16 @@ public function getDerivativeDefinitions($base_plugin_definition) {
             // @todo remove the try/catch as part of
             // http://drupal.org/node/2281645
             try {
-              if (($collection = $this->routeBuilder->getCollectionDuringRebuild()) && $route = $collection->get($route_name)) {
+              if ($collection = $this->routeBuilder->getCollectionDuringRebuild()) {
+                $route = $collection->get($route_name);
               }
               else {
                 $route = $this->routeProvider->getRouteByName($route_name);
               }
-              $this->derivatives[$entity_type_id]['uri_paths'][$link_relation] = $route->getPath();
+
+              if ($route) {
+                $this->derivatives[$entity_type_id]['uri_paths'][$link_relation] = $route->getPath();
+              }
             }
             catch (RouteNotFoundException $e) {
               // If the route does not exist it means we are in a brittle state
diff --git a/core/modules/rest/src/Tests/RESTTestBase.php b/core/modules/rest/src/Tests/RESTTestBase.php
index 146b056..105df19 100644
--- a/core/modules/rest/src/Tests/RESTTestBase.php
+++ b/core/modules/rest/src/Tests/RESTTestBase.php
@@ -8,7 +8,6 @@
 namespace Drupal\rest\Tests;
 
 use Drupal\Core\Session\AccountInterface;
-use Drupal\Core\Url;
 use Drupal\simpletest\WebTestBase;
 
 /**
@@ -63,7 +62,7 @@ protected function setUp() {
   /**
    * Helper function to issue a HTTP request with simpletest's cURL.
    *
-   * @param string $path
+   * @param string $url
    *   The relative URL, e.g. "entity/node/1"
    * @param string $method
    *   HTTP method, one of GET, POST, PUT or DELETE.
@@ -72,7 +71,7 @@ protected function setUp() {
    * @param string $mime_type
    *   The MIME type of the transmitted content.
    */
-  protected function httpRequest($path, $method, $body = NULL, $mime_type = NULL) {
+  protected function httpRequest($url, $method, $body = NULL, $mime_type = NULL) {
     if (!isset($mime_type)) {
       $mime_type = $this->defaultMimeType;
     }
@@ -80,19 +79,14 @@ protected function httpRequest($path, $method, $body = NULL, $mime_type = NULL)
       // GET the CSRF token first for writing requests.
       $token = $this->drupalGet('rest/session/token');
     }
-
-    $options = array('absolute' =>TRUE);
-
     switch ($method) {
       case 'GET':
         // Set query if there are additional GET parameters.
-        if (isset($body)) {
-          $options['query'] = $body;
-        }
+        $options = isset($body) ? array('absolute' => TRUE, 'query' => $body) : array('absolute' => TRUE);
         $curl_options = array(
           CURLOPT_HTTPGET => TRUE,
           CURLOPT_CUSTOMREQUEST => 'GET',
-          CURLOPT_URL => Url::fromUri('base://' . $path, $options)->toString(),
+          CURLOPT_URL => _url($url, $options),
           CURLOPT_NOBODY => FALSE,
           CURLOPT_HTTPHEADER => array('Accept: ' . $mime_type),
         );
@@ -103,7 +97,7 @@ protected function httpRequest($path, $method, $body = NULL, $mime_type = NULL)
           CURLOPT_HTTPGET => FALSE,
           CURLOPT_POST => TRUE,
           CURLOPT_POSTFIELDS => $body,
-          CURLOPT_URL => Url::fromUri('base://' . $path, $options)->toString(),
+          CURLOPT_URL => _url($url, array('absolute' => TRUE)),
           CURLOPT_NOBODY => FALSE,
           CURLOPT_HTTPHEADER => array(
             'Content-Type: ' . $mime_type,
@@ -117,7 +111,7 @@ protected function httpRequest($path, $method, $body = NULL, $mime_type = NULL)
           CURLOPT_HTTPGET => FALSE,
           CURLOPT_CUSTOMREQUEST => 'PUT',
           CURLOPT_POSTFIELDS => $body,
-          CURLOPT_URL => Url::fromUri('base://' . $path, $options)->toString(),
+          CURLOPT_URL => _url($url, array('absolute' => TRUE)),
           CURLOPT_NOBODY => FALSE,
           CURLOPT_HTTPHEADER => array(
             'Content-Type: ' . $mime_type,
@@ -131,7 +125,7 @@ protected function httpRequest($path, $method, $body = NULL, $mime_type = NULL)
           CURLOPT_HTTPGET => FALSE,
           CURLOPT_CUSTOMREQUEST => 'PATCH',
           CURLOPT_POSTFIELDS => $body,
-          CURLOPT_URL => Url::fromUri('base://' . $path, $options)->toString(),
+          CURLOPT_URL => _url($url, array('absolute' => TRUE)),
           CURLOPT_NOBODY => FALSE,
           CURLOPT_HTTPHEADER => array(
             'Content-Type: ' . $mime_type,
@@ -144,7 +138,7 @@ protected function httpRequest($path, $method, $body = NULL, $mime_type = NULL)
         $curl_options = array(
           CURLOPT_HTTPGET => FALSE,
           CURLOPT_CUSTOMREQUEST => 'DELETE',
-          CURLOPT_URL => Url::fromUri('base://' . $path, $options)->toString(),
+          CURLOPT_URL => _url($url, array('absolute' => TRUE)),
           CURLOPT_NOBODY => FALSE,
           CURLOPT_HTTPHEADER => array('X-CSRF-Token: ' . $token),
         );
@@ -155,7 +149,7 @@ protected function httpRequest($path, $method, $body = NULL, $mime_type = NULL)
     $headers = $this->drupalGetHeaders();
     $headers = implode("\n", $headers);
 
-    $this->verbose($method . ' request to: ' . $path .
+    $this->verbose($method . ' request to: ' . $url .
       '<hr />Code: ' . curl_getinfo($this->curlHandle, CURLINFO_HTTP_CODE) .
       '<hr />Response headers: ' . $headers .
       '<hr />Response body: ' . $response);
diff --git a/core/modules/simpletest/src/WebTestBase.php b/core/modules/simpletest/src/WebTestBase.php
index f3e9d86..ec190a0 100644
--- a/core/modules/simpletest/src/WebTestBase.php
+++ b/core/modules/simpletest/src/WebTestBase.php
@@ -26,7 +26,6 @@
 use Drupal\Core\Site\Settings;
 use Drupal\Core\StreamWrapper\PublicStream;
 use Drupal\Core\Datetime\DrupalDateTime;
-use Drupal\Core\Url;
 use Drupal\block\Entity\Block;
 use Symfony\Component\HttpFoundation\Request;
 use Drupal\user\Entity\Role;
@@ -1473,22 +1472,13 @@ protected function isInChildSite() {
   protected function drupalGet($path, array $options = array(), array $headers = array()) {
     $options['absolute'] = TRUE;
 
-    $url = $path;
-
-    // Assume that paths that start with a / are already fully generated
-    // URL's that are just missing $base_root.
-    if (isset($path[0]) && $path[0] == '/') {
-      $url = $GLOBALS['base_root'] . $path;
-    }
     // The URL generator service is not necessarily available yet; e.g., in
     // interactive installer tests.
-    elseif ($this->container->has('url_generator')) {
-      if ($this->container->has('url_generator')) {
-        $url = $this->container->get('url_generator')->generateFromPath($path, $options);
-      }
-      else {
-        $url = $this->getAbsoluteUrl($path);
-      }
+    if ($this->container->has('url_generator')) {
+      $url = $this->container->get('url_generator')->generateFromPath($path, $options);
+    }
+    else {
+      $url = $this->getAbsoluteUrl($path);
     }
 
     // We re-using a CURL connection here. If that connection still has certain
@@ -1975,22 +1965,11 @@ protected function drupalProcessAjaxResponse($content, array $ajax_response, arr
    *
    * @see WebTestBase::getAjaxPageStatePostData()
    * @see WebTestBase::curlExec()
-   * @see \Drupal\Core\Url::fromUri()
+   * @see _url()
    */
   protected function drupalPost($path, $accept, array $post, $options = array()) {
-    $options['absolute'] = TRUE;
-
-    // The URL generator service is not necessarily available yet; e.g., in
-    // interactive installer tests.
-    if ($this->container->has('url_generator')) {
-      $url = $this->container->get('url_generator')->generateFromPath($path, $options);
-    }
-    else {
-      $url = $this->getAbsoluteUrl($path);
-    }
-
     return $this->curlExec(array(
-      CURLOPT_URL => $url,
+      CURLOPT_URL => _url($path, $options + array('absolute' => TRUE)),
       CURLOPT_POST => TRUE,
       CURLOPT_POSTFIELDS => $this->serializePostValues($post),
       CURLOPT_HTTPHEADER => array(
diff --git a/core/modules/system/src/Tests/Menu/BreadcrumbTest.php b/core/modules/system/src/Tests/Menu/BreadcrumbTest.php
index 93a5ded..ab0950c 100644
--- a/core/modules/system/src/Tests/Menu/BreadcrumbTest.php
+++ b/core/modules/system/src/Tests/Menu/BreadcrumbTest.php
@@ -58,8 +58,8 @@ function testBreadCrumbs() {
 
     // Verify Taxonomy administration breadcrumbs.
     $trail = $admin + array(
-        'admin/structure' => t('Structure'),
-      );
+      'admin/structure' => t('Structure'),
+    );
     $this->assertBreadcrumb('admin/structure/taxonomy', $trail);
 
     $trail += array(
@@ -74,8 +74,8 @@ function testBreadCrumbs() {
 
     // Verify Menu administration breadcrumbs.
     $trail = $admin + array(
-        'admin/structure' => t('Structure'),
-      );
+      'admin/structure' => t('Structure'),
+    );
     $this->assertBreadcrumb('admin/structure/menu', $trail);
 
     $trail += array(
@@ -91,9 +91,9 @@ function testBreadCrumbs() {
 
     // Verify Node administration breadcrumbs.
     $trail = $admin + array(
-        'admin/structure' => t('Structure'),
-        'admin/structure/types' => t('Content types'),
-      );
+      'admin/structure' => t('Structure'),
+      'admin/structure/types' => t('Content types'),
+    );
     $this->assertBreadcrumb('admin/structure/types/add', $trail);
     $this->assertBreadcrumb("admin/structure/types/manage/$type", $trail);
     $trail += array(
@@ -102,8 +102,8 @@ function testBreadCrumbs() {
     $this->assertBreadcrumb("admin/structure/types/manage/$type/fields", $trail);
     $this->assertBreadcrumb("admin/structure/types/manage/$type/display", $trail);
     $trail_teaser = $trail + array(
-        "admin/structure/types/manage/$type/display" => t('Manage display'),
-      );
+      "admin/structure/types/manage/$type/display" => t('Manage display'),
+    );
     $this->assertBreadcrumb("admin/structure/types/manage/$type/display/teaser", $trail_teaser);
     $this->assertBreadcrumb("admin/structure/types/manage/$type/delete", $trail);
     $trail += array(
@@ -116,8 +116,8 @@ function testBreadCrumbs() {
     $format = reset($filter_formats);
     $format_id = $format->id();
     $trail = $config + array(
-        'admin/config/content' => t('Content authoring'),
-      );
+      'admin/config/content' => t('Content authoring'),
+    );
     $this->assertBreadcrumb('admin/config/content/formats', $trail);
 
     $trail += array(
@@ -203,8 +203,8 @@ function testBreadCrumbs() {
     );
     $trail = $home + $expected;
     $tree = $expected + array(
-        'node/' . $parent->id() => $parent->menu['title'],
-      );
+      'node/' . $parent->id() => $parent->menu['title'],
+    );
     $trail += array(
       'node/' . $parent->id() => $parent->menu['title'],
     );
diff --git a/core/modules/system/src/Tests/ParamConverter/UpcastingTest.php b/core/modules/system/src/Tests/ParamConverter/UpcastingTest.php
index f7a3ab1..95a7eab 100644
--- a/core/modules/system/src/Tests/ParamConverter/UpcastingTest.php
+++ b/core/modules/system/src/Tests/ParamConverter/UpcastingTest.php
@@ -76,7 +76,7 @@ public function testEntityLanguage() {
     $translation = $node->addTranslation('de');
     $translation->setTitle('Deutscher Titel')->save();
 
-    $this->drupalGet("paramconverter_test/node/" . $node->id() . "/test_language");
+    $this->drupalGet("/paramconverter_test/node/" . $node->id() . "/test_language");
     $this->assertRaw("English label");
     $this->drupalGet("paramconverter_test/node/" . $node->id() . "/test_language", array('language' => $language));
     $this->assertRaw("Deutscher Titel");
diff --git a/core/modules/system/src/Tests/Routing/RouterTest.php b/core/modules/system/src/Tests/Routing/RouterTest.php
index 59812c0..e328759 100644
--- a/core/modules/system/src/Tests/Routing/RouterTest.php
+++ b/core/modules/system/src/Tests/Routing/RouterTest.php
@@ -121,7 +121,7 @@ public function testDynamicRoutes() {
    * Checks that a request with text/html response gets rendered as a page.
    */
   public function testControllerResolutionPage() {
-    $this->drupalGet('router_test/test10');
+    $this->drupalGet('/router_test/test10');
 
     $this->assertRaw('abcde', 'Correct body was found.');
 
@@ -182,7 +182,7 @@ public function testUserAccount() {
   public function testControllerResolutionAjax() {
     // This will fail with a JSON parse error if the request is not routed to
     // The correct controller.
-    $this->drupalGetAJAX('router_test/test10');
+    $this->drupalGetAJAX('/router_test/test10');
 
     $this->assertEqual($this->drupalGetHeader('Content-Type'), 'application/json', 'Correct mime content type was returned');