JUnit:使用构造函数而不是 @Before [英] JUnit: using constructor instead of @Before

问题描述

我使用的是 JUnit 4.我看不出是在构造函数中初始化还是使用由 @Before 注释的专用 init 函数之间的区别.这是否意味着我不必担心它?

I'm using JUnit 4. I can't see the difference between initializing in the constructor or using a dedicated init function annotated by @Before. Does this mean that I don't have to worry about it?

@Before 在构造函数中提供的不仅仅是初始化，是否有任何情况?

Is there any case when @Before gives more than just initializing in the constructor?

推荐答案

不，使用构造函数初始化 JUnit 测试装置在技术上等同于使用 @Before 方法(因为JUnit 为每个 @Test 创建一个测试类的新实例.唯一的(内涵上的)区别是它打破了 @Before 和 @After 之间的对称性，这可能会让一些人感到困惑.恕我直言，最好遵守约定(使用 @Before).

No, using the constructor to initialize your JUnit test fixture is technically equal to using the @Before method (due to the fact that JUnit creates a new instance of the testing class for each @Test). The only (connotational) difference is that it breaks the symmetry between @Before and @After, which may be confusing for some. IMHO it is better to adhere to conventions (which is using @Before).

还要注意，在 JUnit 4 和注解之前，有专门的 setUp() 和 tearDown() 方法 - @Before 和@After 注释取代了这些，但保留了底层逻辑.因此，对于从 JUnit 3 或更早版本迁移的人来说，使用注释还可以使生活更轻松.

Note also that prior to JUnit 4 and annotations, there were dedicated setUp() and tearDown() methods - the @Before and @After annotations replace these, but preserve the underlying logic. So using the annotations also makes life easier for someone migrating from JUnit 3 or earlier versions.

来自评论的更多详细信息:

More details from comments:

• @Before 允许覆盖父类行为，构造函数强制你调用父类构造函数
• 构造函数在之前子类构造函数和@Rule方法运行，@Before在所有这些之后运行
• @Before 期间的异常导致 @After 方法被调用，构造函数中的异常不会

• @Before allows overriding parent class behavior, constructors force you to call parent class constructors
• The constructor runs before subclass constructors and @Rule methods, @Before runs after all of those
• Exceptions during @Before cause @After methods to be called, Exceptions in constructor don't

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