add Testfx and first Gui Test

pom.xml

@@ -43,6 +43,14 @@
             <version>${junit.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.testfx</groupId>
+            <artifactId>testfx-junit5</artifactId>
+            <version>4.0.17</version>
+            <scope>test</scope>
+        </dependency>
+
+
     </dependencies>
 
     <build>

src/test/java/de/hsfulda/onses/GuiTest.java

@@ -0,0 +1,25 @@
+package de.hsfulda.onses;
+
+import javafx.stage.Stage;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.testfx.api.FxAssert;
+import org.testfx.framework.junit5.ApplicationTest;
+import static org.junit.jupiter.api.Assertions.*;
+import static org.testfx.matcher.control.LabeledMatchers.*;
+
+public class GuiTest extends ApplicationTest {
+    private Stage stage;
+
+    @Override
+    public void start(Stage stage) throws Exception {
+        this.stage = stage;
+        new App().start(stage);
+    }
+
+    @Test
+    @DisplayName("Check Window Title")
+    void checkWindowsTitle() {
+        assertEquals("Onses - Uno", stage.getTitle());
+    }
+}