MDL-82373 behat: Wait for alerts before accepting/dismissing them

lib/tests/behat/behat_general.php

@@ -32,8 +32,11 @@
 use Behat\Mink\Exception\DriverException;
 use Behat\Mink\Exception\ElementNotFoundException;
 use Behat\Mink\Exception\ExpectationException;
+use Facebook\WebDriver\Exception\NoSuchAlertException;
 use Facebook\WebDriver\Exception\NoSuchElementException;
 use Facebook\WebDriver\Exception\StaleElementReferenceException;
+use Facebook\WebDriver\WebDriverAlert;
+use Facebook\WebDriver\WebDriverExpectedCondition;
 
 /**
  * Cross component steps definitions.
@@ -262,20 +265,34 @@ public function i_close_all_opened_windows() {
         $this->getSession()->switchToWindow($names[0]);
     }
 
+    /**
+     * Wait for an alert to be displayed.
+     *
+     * @return WebDriverAlert
+     */
+    public function wait_for_alert(): WebDriverAlert {
+        $webdriver = $this->getSession()->getDriver()->getWebdriver();
+        $webdriver->wait()->until(WebDriverExpectedCondition::alertIsPresent());
+
+        return $webdriver->switchTo()->alert();
+    }
+
     /**
      * Accepts the currently displayed alert dialog. This step does not work in all the browsers, consider it experimental.
      * @Given /^I accept the currently displayed dialog$/
      */
     public function accept_currently_displayed_alert_dialog() {
-        $this->getSession()->getDriver()->getWebDriver()->switchTo()->alert()->accept();
+        $alert = $this->wait_for_alert();
+        $alert->accept();
     }
 
     /**
      * Dismisses the currently displayed alert dialog. This step does not work in all the browsers, consider it experimental.
      * @Given /^I dismiss the currently displayed dialog$/
      */
     public function dismiss_currently_displayed_alert_dialog() {
-        $this->getSession()->getDriver()->getWebDriver()->switchTo()->alert()->dismiss();
+        $alert = $this->wait_for_alert();
+        $alert->dismiss();
     }
 
     /**