How do I write JUnit tests for my Java application?

How do I write JUnit tests for my Java application?

To write JUnit tests, you need to create a test class and annotate your test methods with @Test. Can you provide a specific example?

Sure! I have a method that adds two numbers. How would I test that?

You can create a test method like this:

@Test
public void testAdd() {
    Calculator calc = new Calculator();
    assertEquals(5, calc.add(2, 3));
}

This checks if the add method returns the correct sum.

What if the method throws an exception?

You can use the @Test(expected = Exception.class) annotation to test for exceptions. For example:

@Test(expected = IllegalArgumentException.class)
public void testAddWithNegativeNumbers() {
    Calculator calc = new Calculator();
    calc.add(-1, 3);
}