diff -u b/core/modules/toolbar/src/Tests/ToolbarCacheContextsTest.php b/core/modules/toolbar/src/Tests/ToolbarCacheContextsTest.php
--- b/core/modules/toolbar/src/Tests/ToolbarCacheContextsTest.php
+++ b/core/modules/toolbar/src/Tests/ToolbarCacheContextsTest.php
@@ -68,29 +68,29 @@
    */
   public function testToolbarCacheContextsCaller() {
     // Test with default combination and permission to see toolbar.
-    $this->testToolbarCacheContexts(['user']);
+    $this->testToolbarCacheContexts(['user'], 'Expected cache contexts found for default combination and permission to see toolbar.');
 
     // Test without user toolbar tab. User module is a required module so we have to
     // manually remove the user toolbar tab.
     \Drupal::service('module_installer')->install(['toolbar_disable_user_toolbar']);
-    $this->testToolbarCacheContexts(['user.permissions']);
+    $this->testToolbarCacheContexts(['user.permissions'], 'Expected cache contexts found without user toolbar tab.');
 
     // Test with the toolbar and contextual enabled.
     \Drupal::service('module_installer')->install(['contextual']);
     $this->adminUser2 = $this->drupalCreateUser(array_merge($this->perms, ['access contextual links']));
-    $this->testToolbarCacheContexts(['user.permissions']);
+    $this->testToolbarCacheContexts(['user.permissions'], 'Expected cache contexts found with contextual module enabled.');
     \Drupal::service('module_installer')->uninstall(['contextual']);
 
     // Test with the tour module enabled.
     \Drupal::service('module_installer')->install(['tour']);
     $this->adminUser2 = $this->drupalCreateUser(array_merge($this->perms, ['access tour']));
-    $this->testToolbarCacheContexts(['user.permissions']);
+    $this->testToolbarCacheContexts(['user.permissions'], 'Expected cache contexts found with tour module enabled.');
     \Drupal::service('module_installer')->uninstall(['tour']);
 
     // Test with shortcut module enabled.
     \Drupal::service('module_installer')->install(['shortcut']);
     $this->adminUser2 = $this->drupalCreateUser(array_merge($this->perms, ['access shortcuts', 'administer shortcuts']));
-    $this->testToolbarCacheContexts(['user']);
+    $this->testToolbarCacheContexts(['user'], 'Expected cache contexts found with shortcut module enabled.');
   }
 
   /**
@@ -98,8 +98,10 @@
    *
    * @param string[] $cache_contexts
    *   Expected cache contexts for both users.
+   * @param string $message
+   *   (optional) A verbose message to output.
    */
-  private function testToolbarCacheContexts(array $cache_contexts) {
+  private function testToolbarCacheContexts(array $cache_contexts, $message = NULL) {
     // Caches have to be rebuilt since modules might have added some routes.
     drupal_flush_all_caches();
 
@@ -113,13 +115,13 @@
     // Assert contexts for user1 which has only default permissions.
     $this->drupalLogin($this->adminUser);
     $this->drupalGet('test-page');
-    $this->assertCacheContexts($cache_contexts);
+    $this->assertCacheContexts($cache_contexts, $message);
     $this->drupalLogout();
 
     // Assert contexts for user2 which has some additional permissions.
     $this->drupalLogin($this->adminUser2);
     $this->drupalGet('test-page');
-    $this->assertCacheContexts($cache_contexts);
+    $this->assertCacheContexts($cache_contexts, $message);
   }
 
 }
diff -u b/core/modules/toolbar/tests/modules/toolbar_disable_user_toolbar/toolbar_disable_user_toolbar.info.yml b/core/modules/toolbar/tests/modules/toolbar_disable_user_toolbar/toolbar_disable_user_toolbar.info.yml
--- b/core/modules/toolbar/tests/modules/toolbar_disable_user_toolbar/toolbar_disable_user_toolbar.info.yml
+++ b/core/modules/toolbar/tests/modules/toolbar_disable_user_toolbar/toolbar_disable_user_toolbar.info.yml
@@ -1,4 +1,4 @@
-name: 'Disbale user toolbar'
+name: 'Disable user toolbar'
 type: module
 description: 'Support module for testing toolbar without user toolbar'
 package: Testing
only in patch2:
unchanged:
--- a/core/modules/system/src/Tests/Cache/AssertPageCacheContextsAndTagsTrait.php
+++ b/core/modules/system/src/Tests/Cache/AssertPageCacheContextsAndTagsTrait.php
@@ -102,12 +102,14 @@ protected function assertCacheTags(array $expected_tags) {
    *
    * @param string[] $expected_contexts
    *   The expected cache contexts.
+   * @param string $message
+   *   (optional) A verbose message to output.
    */
-  protected function assertCacheContexts(array $expected_contexts) {
+  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);
+    $this->assertIdentical($actual_contexts, $expected_contexts, $message);
     if ($actual_contexts !== $expected_contexts) {
       debug('Missing cache contexts: ' . implode(',', array_diff($actual_contexts, $expected_contexts)));
       debug('Unwanted cache contexts: ' . implode(',', array_diff($expected_contexts, $actual_contexts)));