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What is the main difference between
@Before and @BeforeClass @BeforeEach and @BeforeAll @After and @AfterClass According to the JUnit Api @Before is used in the following case:
When writing tests, it is common to find that several tests need similar objects created before they can run.
Whereas @BeforeClass can be used to establish a database connection. But couldn't @Before do the same?
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If you're certain that the tests don't make any changes to those conditions, you can use beforeAll (which will run once). If the tests do make changes to those conditions, then you would need to use beforeEach , which will run before every test, so it can reset the conditions for the next one.
@BeforeAll is used to signal that the annotated method should be executed before all tests in the current test class. In contrast to @BeforeEach methods, @BeforeAll methods are only executed once for a given test class.
@BeforeTest method executes only once before the first @Test method. @BeforeClass executes before each class. If there are separate @BeforeTest and @BeforeClass methods in different classes, then all the @BeforeTest methods will execute first but @BeforeClass methods will be executing as per the respective classes.
@BeforeEach is used to signal that the annotated method should be executed before each @Test method in the current test class.
The code marked @Before is executed before each test, while @BeforeClass runs once before the entire test fixture. If your test class has ten tests, @Before code will be executed ten times, but @BeforeClass will be executed only once.
In general, you use @BeforeClass when multiple tests need to share the same computationally expensive setup code. Establishing a database connection falls into this category. You can move code from @BeforeClass into @Before, but your test run may take longer. Note that the code marked @BeforeClass is run as static initializer, therefore it will run before the class instance of your test fixture is created.
In JUnit 5, the tags @BeforeEach and @BeforeAll are the equivalents of @Before and @BeforeClass in JUnit 4. Their names are a bit more indicative of when they run, loosely interpreted: 'before each tests' and 'once before all tests'.
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Difference between each annotation are :
+-------------------------------------------------------------------------------------------------------+ ¦ Feature ¦ Junit 4 ¦ Junit 5 ¦ ¦--------------------------------------------------------------------------+--------------+-------------¦ ¦ Execute before all test methods of the class are executed. ¦ @BeforeClass ¦ @BeforeAll ¦ ¦ Used with static method. ¦ ¦ ¦ ¦ For example, This method could contain some initialization code ¦ ¦ ¦ ¦-------------------------------------------------------------------------------------------------------¦ ¦ Execute after all test methods in the current class. ¦ @AfterClass ¦ @AfterAll ¦ ¦ Used with static method. ¦ ¦ ¦ ¦ For example, This method could contain some cleanup code. ¦ ¦ ¦ ¦-------------------------------------------------------------------------------------------------------¦ ¦ Execute before each test method. ¦ @Before ¦ @BeforeEach ¦ ¦ Used with non-static method. ¦ ¦ ¦ ¦ For example, to reinitialize some class attributes used by the methods. ¦ ¦ ¦ ¦-------------------------------------------------------------------------------------------------------¦ ¦ Execute after each test method. ¦ @After ¦ @AfterEach ¦ ¦ Used with non-static method. ¦ ¦ ¦ ¦ For example, to roll back database modifications. ¦ ¦ ¦ +-------------------------------------------------------------------------------------------------------+ Most of annotations in both versions are same, but few differs.
Reference
Order of Execution.
Dashed box -> optional annotation.
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