diff --git a/core/modules/system/src/Tests/Cache/AssertPageCacheContextsAndTagsTrait.php b/core/modules/system/src/Tests/Cache/AssertPageCacheContextsAndTagsTrait.php
index 5cfac80..4893c54 100644
--- a/core/modules/system/src/Tests/Cache/AssertPageCacheContextsAndTagsTrait.php
+++ b/core/modules/system/src/Tests/Cache/AssertPageCacheContextsAndTagsTrait.php
@@ -104,16 +104,20 @@ protected function assertCacheTags(array $expected_tags) {
    *   The expected cache contexts.
    * @param string $message
    *   (optional) A verbose message to output.
+   *
+   * @return
+   *   TRUE if the assertion succeeded, FALSE otherwise.
    */
   protected function assertCacheContexts(array $expected_contexts, $message = NULL) {
     $actual_contexts = $this->getCacheHeaderValues('X-Drupal-Cache-Contexts');
     sort($expected_contexts);
     sort($actual_contexts);
-    $this->assertIdentical($actual_contexts, $expected_contexts, $message);
-    if ($actual_contexts !== $expected_contexts) {
+    $return = $this->assertIdentical($actual_contexts, $expected_contexts, $message);
+    if (!$return) {
       debug('Missing cache contexts: ' . implode(',', array_diff($actual_contexts, $expected_contexts)));
       debug('Unwanted cache contexts: ' . implode(',', array_diff($expected_contexts, $actual_contexts)));
     }
+    return $return;
   }
 
   /**
diff --git a/core/modules/toolbar/src/Tests/ToolbarCacheContextsTest.php b/core/modules/toolbar/src/Tests/ToolbarCacheContextsTest.php
index 0bf88b0..fb8c14c 100644
--- a/core/modules/toolbar/src/Tests/ToolbarCacheContextsTest.php
+++ b/core/modules/toolbar/src/Tests/ToolbarCacheContextsTest.php
@@ -100,6 +100,9 @@ public function testToolbarCacheContextsCaller() {
    *   Expected cache contexts for both users.
    * @param string $message
    *   (optional) A verbose message to output.
+   *
+   * @return
+   *   TRUE if the assertion succeeded, FALSE otherwise.
    */
   protected function assertToolbarCacheContexts(array $cache_contexts, $message = NULL) {
     // Default cache contexts that should exist on all test cases.
@@ -112,13 +115,21 @@ protected function assertToolbarCacheContexts(array $cache_contexts, $message =
     // Assert contexts for user1 which has only default permissions.
     $this->drupalLogin($this->adminUser);
     $this->drupalGet('test-page');
-    $this->assertCacheContexts($cache_contexts, $message);
+    $return = $this->assertCacheContexts($cache_contexts);
     $this->drupalLogout();
 
     // Assert contexts for user2 which has some additional permissions.
     $this->drupalLogin($this->adminUser2);
     $this->drupalGet('test-page');
-    $this->assertCacheContexts($cache_contexts, $message);
+    $return = $return && $this->assertCacheContexts($cache_contexts);
+
+    if ($return) {
+      $this->pass($message);
+    }
+    else {
+      $this->fail($message);
+    }
+    return $return;
   }
 
   /**
@@ -130,8 +141,9 @@ protected function assertToolbarCacheContexts(array $cache_contexts, $message =
   protected function installModules(array $module_list) {
     \Drupal::service('module_installer')->install($module_list);
 
-    // Caches have to be rebuilt since modules might have added some routes.
-    drupal_flush_all_caches();
+    // Installing modules updates the container and needs a router rebuild.
+    $this->container = \Drupal::getContainer();
+    $this->container->get('router.builder')->rebuildIfNeeded();
   }