Added an IT for the long-polling push case

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

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2000-2018 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.flow.uitest.ui;
+
+import com.vaadin.flow.component.html.Div;
+import com.vaadin.flow.component.html.NativeButton;
+import com.vaadin.flow.component.html.Span;
+import com.vaadin.flow.component.page.Push;
+import com.vaadin.flow.router.Route;
+import com.vaadin.flow.shared.ui.Transport;
+
+/**
+ * Class for reproducing the bug https://github.com/vaadin/flow/issues/4353
+ */
+@Route("com.vaadin.flow.uitest.ui.LongPollingPushView")
+@Push(transport = Transport.LONG_POLLING)
+public class LongPollingPushView extends AbstractDivView {
+
+    public LongPollingPushView() {
+        Div parent = new Div();
+        Span child = new Span("Some text");
+        child.setId("child");
+        parent.add(child);
+        add(parent);
+        parent.setVisible(false);
+
+        NativeButton visibility = new NativeButton("Toggle visibility",
+                e -> parent.setVisible(!parent.isVisible()));
+        visibility.setId("visibility");
+        add(visibility);
+    }
+}

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

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+/*
+ * Copyright 2000-2018 Vaadin Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.vaadin.flow.uitest.ui;
+
+import org.junit.Assert;
+import org.junit.Test;
+import org.openqa.selenium.By;
+import org.openqa.selenium.WebElement;
+
+import com.vaadin.flow.testutil.ChromeBrowserTest;
+
+public class LongPollingPushIT extends ChromeBrowserTest {
+
+    @Test
+    public void openPage_thereAreNoErrorsInTheConsole() {
+        open();
+        checkLogsForErrors();
+
+        waitForElementNotPresent(By.id("child"));
+
+        WebElement button = findElement(By.id("visibility"));
+        button.click();
+
+        waitForElementPresent(By.id("child"));
+
+        WebElement span = findElement(By.id("child"));
+        Assert.assertEquals("Some text", span.getText());
+        checkLogsForErrors();
+    }
+
+}