Difference between @Before, @BeforeClass, @BeforeEach and @BeforeAll

问题: What is the main difference between @Before and @BeforeClass and in JUnit 5 @BeforeEach and @BeforeAll @After and @AfterClass According to the...

问题:

What is the main difference between

  • @Before and @BeforeClass
    • and in JUnit 5 @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?


回答1:

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'.


回答2:

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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  • 发表于 2018-07-11 21:35
  • 阅读 ( 294 )
  • 分类:sof

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