@Before、@BeforeClass、@BeforeEach 和 @BeforeAll 之间的区别 [英] Difference between @Before, @BeforeClass, @BeforeEach and @BeforeAll

问题描述

两者的主要区别是什么

• @Before 和 @BeforeClass
  • 以及在 JUnit 5 @BeforeEach 和 @BeforeAll
  • @Before and @BeforeClass
    • and in JUnit 5 @BeforeEach and @BeforeAll

    根据JUnit Api @Before 在下面使用案例:

    According to the JUnit Api @Before is used in the following case:

    在编写测试时，通常会发现多个测试需要创建相似的对象才能运行.

    When writing tests, it is common to find that several tests need similar objects created before they can run.

    而@BeforeClass 可用于建立数据库连接.但是 @Before 不能这样做吗?

    Whereas @BeforeClass can be used to establish a database connection. But couldn't @Before do the same?

    推荐答案

    标记为@Before的代码在每次测试前执行，而@BeforeClass在整个测试前运行一次测试夹具.如果你的测试类有十个测试，@Before 代码会被执行十次，而 @BeforeClass 只会被执行一次.

    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.

    通常，当多个测试需要共享相同的计算成本高的设置代码时，您可以使用 @BeforeClass.建立数据库连接就属于这一类.您可以将代码从 @BeforeClass 移动到 @Before，但您的测试运行可能需要更长的时间.请注意，标记为 @BeforeClass 的代码作为静态初始化程序运行，因此它将在创建测试装置的类实例之前运行.

    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.

    在 JUnit 5 中，标签 @BeforeEach 和 @BeforeAll 是 JUnit 4 中 @Before 和 @BeforeClass 的等价物.它们的名称更能说明它们何时运行，大致解释如下:在每次测试之前'和'在所有测试之前一次'.

    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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