SimpleTest.java

import main.Utility;
import org.junit.jupiter.api.Test;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.fail;

public class SimpleTest {


    @Test
    public void myTest() {
//        fail("This test will fail");
        int expected = 5;
        int actual = 5;
        assertEquals(expected, actual);
    }

    @Test
    public void testClass() {

        double expected = 10.234543;
        double actual = Utility.add(10, 0.234543);

        assertEquals(expected, actual);
    }

}

Utility.java

package main;

public class Utility {

    public static double add(int x, double y) {
        return x + y;
    }

}