only in patch2:
unchanged:
--- /dev/null
+++ b/core/profiles/demo_umami/tests/src/FunctionalJavascript/DemoUmamiMainMenuTest.php
@@ -0,0 +1,79 @@
+<?php
+
+namespace Drupal\Tests\demo_umami\FunctionalJavascripts;
+
+use Drupal\FunctionalJavascriptTests\WebDriverTestBase;
+
+/**
+ * Tests behaviour of main menu block in Umami demo profile.
+ *
+ * @group demo_umami
+ *
+ * @todo this class tests menu behaviour at narrow breakpoint
+ *   do we need another CLASS to test menu behaviour at wide breakpoint
+ */
+class DemoUmamiMainMenuTest extends WebDriverTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $profile = 'demo_umami';
+
+  /**
+   * Tests behaviour of main menu disclosure button, using enter key.
+   */
+  public function testMainMenuOpenClose() {
+
+    // Test menu behaviour with a narrow viewport.
+    $this->getSession()->resizeWindow(400, 700);
+
+    $assert = $this->assertSession();
+
+    $this->drupalGet('');
+
+    // @todo remove screenshot
+    $this->createScreenshot('umamu2.jpg');
+
+    // @todo remove trivial assert, this is just to get me started
+    $assert->pageTextContains('pasta');
+
+    // Various checks to confirm the menu behaviour is initialized correctly.
+    // assert button is visible
+    $button = $assert->elementExists('css', '.menu-main-toggle');
+    $assert->assert($button->isVisible(), 'Menu button is not visible.');
+
+    //assert button is labelled - can we test the *computed accessible name*?
+    // workaround is to test for aria-label="foo", but that's an implementation detail, rather than the desiered end itself...
+
+    //assert button has aria-controls
+
+    //assert button has aria-expanded, initialized to false
+    $assert->assert($button->getAttribute('aria-expanded') === 'false', 'aria-expanded attribute not initialized correctly.');
+
+    //assert menu UL is collapsed (class) - do we actually need to test that? It's a implementation detail, not a behaviour...
+    //assert menu links (home, articles, recipes) are NOT visible - this is the actual behaviour
+    // assert button is focusable?
+
+    // interaction behaviour, open it
+    // WORLD - THE TIME HAS COME TO PUSH THE BUTTON
+    // assert button now says aria-expanded=true
+    // assert button still has focus
+    // assert menu UL has expanded class (maybe)
+    // assert menu links are visible
+
+    // interaction behaviour, close it
+    // WORLD - THE TIME HAS COME TO PUSH THE BUTTON
+    // assert button now says aria-expanded=false
+    // assert button still has focus
+    // assert menu UL is collapsed (maybe)
+    // assert menu links are NOT visible
+
+    // @TODO same as previous test, but do it with SPACEBAR.
+
+    // @TODO do we need to run tests for "click", separate to keypress?
+
+    // @todo resize window, wide viewport
+    // no button visible, links visible.
+  }
+
+}