test: DialogShortcutIT Wait for child element presence before perform…

…ing assertions (#12830)

Sometimes findElements(By.tagNvame("div")) seems to return results
before server roundtrips are completed, so list of elements is missing
elements. Performing a direct searching for child element by xpath
(findElement(By.xpath("div[N]")))) seem always to work.
To be noted that xpath position is 1 based

Fixes #10481, #10487, #10491

flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/ComplexDialogShortcutIT.java

@@ -1,12 +1,10 @@
 package com.vaadin.flow.uitest.ui;
 
-import org.junit.Ignore;
 import org.junit.Test;
 import org.openqa.selenium.By;
 
 import static com.vaadin.flow.uitest.ui.DialogShortcutView.REUSABLE_DIALOG_ID;
 
-@Ignore("Flaky test #10481, #10487, #10491")
 public class ComplexDialogShortcutIT extends DialogShortcutIT {
 
     @Test

flow-tests/test-root-context/src/test/java/com/vaadin/flow/uitest/ui/DialogShortcutIT.java

@@ -9,14 +9,12 @@
 import com.vaadin.testbench.TestBenchElement;
 import org.junit.Assert;
 import org.junit.Before;
-import org.junit.Ignore;
 import org.junit.Test;
 import org.openqa.selenium.By;
 import org.openqa.selenium.WebElement;
 
 import static com.vaadin.flow.uitest.ui.DialogShortcutView.REUSABLE_DIALOG_ID;
 
-@Ignore("Flaky test #10481, #10487, #10491")
 public class DialogShortcutIT extends ChromeBrowserTest {
 
     private TestBenchElement eventLog;
@@ -202,8 +200,8 @@ protected void validateLatestShortcutEvent(int eventCounter,
 
     private void validateShortcutEvent(int indexFromTop, int eventCounter,
             String eventSourceId) {
-        final WebElement latestEvent = eventLog.findElements(By.tagName("div"))
-                .get(indexFromTop);
+        final WebElement latestEvent = waitUntil(driver -> eventLog.findElement(
+                By.xpath(String.format("div[%d]", indexFromTop + 1))));
         Assert.assertEquals(
                 "Invalid latest event with " + indexFromTop + ":" + ":"
                         + eventSourceId,