I provide this post for both IntelliJ and Eclipse.

Eclipse:

To add unit tests to your project, please follow these steps (I am using Eclipse in order to write this test):

1- Click on New -> Java Project.

2- Enter your project name and click on finish.

3- Right click on your project. Then, click on New -> Class.

4- Enter your class name and click on finish.

Then, complete the class like this:

public class Math {
    int a, b;
    Math(int a, int b) {
        this.a = a;
        this.b = b;
    }
    public int add() {
        return a + b;
    }
}

5- Click on File -> New -> JUnit Test Case.

6- Check setUp() and click on finish. The method setUp() will be the place where you initialize your test.

7- Click on OK.

8- Here, I simply add 7 and 10. So, I expect the answer to be 17. Complete your test class like this:

import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;
public class MathTest {
    Math math;
    @Before
    public void setUp() throws Exception {
        math = new Math(7, 10);
    }
    @Test
    public void testAdd() {
        Assert.assertEquals(17, math.add());
    }
}

9- Right-click on your test class in package explorer and click on Run as -> JUnit Test.

10- This is the result of the test:

IntelliJ: Note that I used IntelliJ IDEA community 2020.1 for the screenshots. Also, you need to set up your JRE before following these steps. I am using JDK 11.0.4.

1- Right-click on the main folder of your project: -> New -> Directory. You should call this 'test'. 2- Right-click on the test folder and create the proper package. I suggest creating the same package names as the original class. Then, you right-click on the test directory -> mark directory as -> test sources root. 3- In the right package in the test directory, you need to create a Java class (I suggest to use Test.java). 4- In the created class, type '@Test'. Then, among the options that IntelliJ gives you, select Add 'JUnitx' to classpath. 5- Write your test method in your test class. The method signature looks like this:

@Test
public void test<name of original method>(){
...
}

You can do your assertions like below:

Assertions.assertTrue(f.flipEquiv(node1_1, node2_1));

These are the imports that I added:

import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;

This is the test that I wrote:

You can check your methods like this:

Assertions.assertEquals(<Expected>,<actual>);
Assertions.assertTrue(<actual>);
...

For running your unit tests, right-click on the test and click on Run .

If your test passes, the results will look like this: