Issue #2937073 by tim.plunkett, Saviktor, tedbow: Improve robustness of FieldBlockTest

core/modules/layout_builder/tests/src/FunctionalJavascript/FieldBlockTest.php

@@ -91,7 +91,7 @@ public function testFieldBlock() {
     $assert_session->fieldNotExists('settings[formatter][settings][format_type]');
     $assert_session->fieldExists('settings[formatter][settings][granularity]');
     $page->pressButton('Save block');
-    $assert_session->pageTextContains('The block configuration has been saved.');
+    $this->assertTrue($assert_session->waitForText('The block configuration has been saved.'));
 
     // Configure the block and change the formatter again.
     $this->clickLink('Configure');
@@ -101,7 +101,7 @@ public function testFieldBlock() {
     $page->selectFieldOption('settings[formatter][settings][format_type]', 'long');
 
     $page->pressButton('Save block');
-    $assert_session->pageTextContains('The block configuration has been saved.');
+    $this->assertTrue($assert_session->waitForText('The block configuration has been saved.'));
 
     // Assert that the field value is updated.
     $this->clickLink('Configure');

core/tests/Drupal/FunctionalJavascriptTests/JSWebAssert.php

@@ -101,6 +101,26 @@ public function waitForElementVisible($selector, $locator, $timeout = 10000) {
     return $result;
   }
 
+  /**
+   * Waits for the specified text and returns its element when available.
+   *
+   * @param string $text
+   *   The text to wait for.
+   * @param int $timeout
+   *   (Optional) Timeout in milliseconds, defaults to 10000.
+   *
+   * @return \Behat\Mink\Element\NodeElement|null
+   *   The page element node if found and visible, NULL if not.
+   */
+  public function waitForText($text, $timeout = 10000) {
+    $page = $this->session->getPage();
+    return $page->waitFor($timeout / 1000, function () use ($page, $text) {
+      $actual = preg_replace('/\s+/u', ' ', $page->getText());
+      $regex = '/' . preg_quote($text, '/') . '/ui';
+      return (bool) preg_match($regex, $actual);
+    });
+  }
+
   /**
    * Waits for a button (input[type=submit|image|button|reset], button) with
    * specified locator and returns it.