The @Before annotation can be used to accompany the @Test methods. Methods tagged with @Before will run before each test method and look like the following:

@Before
public void beforeEachTest() {
  // Something multiple tests use
}

They’re typically used if multiple test methods share a similarly created object or set of variables. Placing those inside the @Before annotated method ensures those objects are always freshly created and have the same starting attributes upon instantiation. This allows each test to work with those objects and variables without needing to create them themselves inside their own test bodies.

If we look at the example we covered in the previous exercise, we created the Human named “Sam” twice in the exact same fashion. Now that we know about the @Before annotation, we could instead place the creation of sam inside of the @Before method:

Human sam;

@Before
public void createSam() {
  sam = new Human(“Sam”, 100);
}

@Test
public void testHuman() {
  assertEquals(100, sam.getHitpoints());
  assertEquals(“Sam”, sam.getName());
}

@Test
public void testHumanTakeDamage() {
  assertEquals(100, sam.getHitpoints());
  sam.takeDamage(10);
  assertEquals(90, sam.getHitpoints());
}

This is different from just making sam a class variable, which is also visible by all tests because the @Before will re-run before each test. This means if tests modify the sam variable in any way, it ensures sam gets reset before the next test runs.

There’s another variant of the @Before annotation that will let us create a method that will run one time before all tests instead of multiple times before each test. This is done by using the @BeforeClass annotation.

@Before and @BeforeClass both have their unique uses, making them valuable tools for JUnit testing.