Some fixes, create initial test class

javafx-template/src/test/java/app/AppTest.java

@@ -0,0 +1,24 @@
+package app;
+
+import javafx.fxml.FXMLLoader;
+import javafx.scene.Parent;
+import javafx.scene.Scene;
+import javafx.stage.Stage;
+
+import java.io.IOException;
+
+import org.testfx.framework.junit5.ApplicationTest;
+
+/**
+ * TestFX App test
+ */
+public class AppTest extends ApplicationTest {
+
+    @Override
+    public void start(Stage stage) throws IOException {
+        FXMLLoader fxmlLoader = new FXMLLoader(this.getClass().getResource("App.fxml"));
+        Parent parent = fxmlLoader.load();
+        stage.setScene(new Scene(parent));
+        stage.show();
+    }
+}