add ExampleTest for Surefire

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

@@ -0,0 +1,14 @@
+package de.hsfulda.onses;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
+
+public class ExampleTest {
+    @Test
+    @DisplayName("Example Test")
+    public void exampleTest() {
+        int test = 1 + 1;
+        assertEquals(2, test);
+    }
+}