diff --git a/core/modules/block/src/Tests/BlockDemoTest.php b/core/modules/block/src/Tests/BlockDemoTest.php
index afda648..a1e9d09 100644
--- a/core/modules/block/src/Tests/BlockDemoTest.php
+++ b/core/modules/block/src/Tests/BlockDemoTest.php
@@ -31,36 +31,37 @@ public function testBlockDemo() {
     $admin_user = $this->drupalCreateUser(array('administer blocks', 'administer themes'));
     $this->drupalLogin($admin_user);
 
-    // Install default theme and confirm we have access to the demo page for it.
+    // Confirm we have access to the block demo page for the default theme.
     $config = \Drupal::config('system.theme');
     $default_theme = $config->get('default');
-    \Drupal::service('theme_handler')->install(array($default_theme));
-    $edit['admin_theme'] = $default_theme;
-    $this->drupalPostForm('admin/appearance', $edit, t('Save configuration'));
     $this->drupalGet('admin/structure/block/demo/' . $default_theme);
     $this->assertResponse(200);
     $this->assertLinkByHref('admin/structure/block');
     $this->assertNoLinkByHref('admin/structure/block/list/' . $default_theme);
 
-    // Install bartik theme and confirm we have access to the demo page for it.
-    \Drupal::service('theme_handler')->install(array('bartik'));
-    $edit['admin_theme'] = 'bartik';
-    $this->drupalPostForm('admin/appearance', $edit, t('Save configuration'));
-    $this->drupalGet('admin/structure/block/demo/bartik');
-    $this->assertResponse(200);
-    $this->assertLinkByHref('admin/structure/block/list/bartik');
+    // All available themes in core.
+    $available_themes = array(
+      'bartik',
+      'classy',
+      'seven',
+      'stark',
+    );
 
-    // Install seven theme and confirm we have access to the demo page for it.
-    \Drupal::service('theme_handler')->install(array('seven'));
-    $edit['admin_theme'] = 'seven';
-    $this->drupalPostForm('admin/appearance', $edit, t('Save configuration'));
-    $this->drupalGet('admin/structure/block/demo/seven');
-    $this->assertResponse(200);
-    $this->assertLinkByHref('admin/structure/block/list/seven');
+    // All available themes minute minus the default theme.
+    $themes = array_diff($available_themes, array($default_theme));
 
-    // Make sure there is no access for an invalid theme.
+    foreach ($themes as $theme) {
+      // Install theme.
+      \Drupal::service('theme_handler')->install(array($theme));
+      // Confirm access to the block demo page for the theme.
+      $this->drupalGet('admin/structure/block/demo/' . $theme);
+      $this->assertResponse(200);
+      // Confirm existence of link for "Exit block region demonstration".
+      $this->assertLinkByHref('admin/structure/block/list/' . $theme);
+    }
+
+    // Confirm access to the block demo page is denied for an invalid theme.
     $this->drupalGet('admin/structure/block/demo/invalid_theme');
     $this->assertResponse(403);
-
   }
 }