JUnit5-Jupiter:组合(="meta")注释无法解析为注释定义 [英] JUnit5-Jupiter: Composed (="meta") annotation does not resolve to annotation definition

问题描述

我定义了自己的JUnit批注:

I defined my own JUnit annotation:

@ParameterizedTest
@MethodSource("myorg.qa.ccrtesting.DataProviders#standardDataProvider")
@Tags({@Tag("ccr"), @Tag("standard")})
public @interface CcrStandardTest {
}

然后，我可以在测试中使用该批注:

Then, I was able to use that annotation in my tests:

@CcrStandardTest
public void E0010_contact_standard (String testData) {
...

• 我的跑步配置:
  JVM选项:-ea
  类:myorg.qa.ccrtesting.ccrstandardtests.CcrStanConTest-这是IDE提出的(已验证为指向正确的类，其中包含我的原型测试方法)
• My run configuration:
  JVM options: -ea
  Class: myorg.qa.ccrtesting.ccrstandardtests.CcrStanConTest - This was suggested by the IDE (and is verified to point to the correct class, which holds my prototype test method)

但是，结果为:jupiter.api.extension.ParameterResolutionException: No ParameterResolver registered for parameter [java.lang.String arg0] in method [public void...

• 我尝试从测试方法签名中删除String testData，但是JUnit没有执行任何测试:No tests found

• I tried removing String testData from the test method signature but then JUnit is not executing any tests: No tests found

当我在原型测试方法上方添加@Test时，它会执行，但是:

When I add @Test above my prototype test method, it executes but:

1. 在@CcrStandardTest下定义的注释似乎都没有应用
2. IDE建议suspicious combination @Test and parameterized source
   (我已经知道@ParameterizedTest暗示@Test，只是不确定为什么IDE能够找到自定义注释，而JUnit却找不到?)
1. It seems like none of the annotations I defined under @CcrStandardTest are applied
2. IDE suggests suspicious combination @Test and parameterized source
   (I already know @ParameterizedTest implies @Test, just not sure why IDE is able to find the custom annotation but JUnit isn't?)

推荐答案

您已经发现，您需要添加

As you've discovered, you need to add @Retention(RUNTIME) to your composed annotation in order for JUnit to see it. Annotations in Java have three different retention policies:

• RetentionPolicy.SOURCE

注释将被编译器丢弃.

Annotations are to be discarded by the compiler.

• RetentionPolicy.CLASS

• RetentionPolicy.CLASS

  注释由编译器记录在类文件中，但VM不必在运行时保留. 这是默认行为. [添加了重点]

• RetentionPolicy.RUNTIME

• RetentionPolicy.RUNTIME

  注释由编译器记录在类文件中，并在运行时由VM保留，以便可以通过反射方式读取.

  Annotations are to be recorded in the class file by the compiler and retained by the VM at run time, so they may be read reflectively.

如上所述，如果您未明确添加@Retention(...)，则会使用CLASS策略.这不适用于JUnit，因为JUnit不会扫描*.class文件(即字节码)中的注释，而是以反射方式扫描 loaded 类以找到测试方法.没有RUNTIME保留策略，您的注释将无法反射访问，因此JUnit永远不会看到它，因此不会执行测试.

As I emphasized above, if you don't explicitly add @Retention(...) then the CLASS policy is used. This won't work with JUnit because JUnit doesn't scan the *.class files (i.e. byte-code) for the annotations, it scans the loaded classes reflectively to find test methods. Without a RUNTIME retention policy your annotation is not reflectively accessible, thus JUnit never sees it and consequently doesn't execute the test.

指示注释类型适用的上下文.在JLS 9.6.4.1中指定了可以在其中应用注释类型的声明上下文和类型上下文，并在源代码中用如果注释类型T上不存在@Target元注释，则可以将类型为T的注释写为除类型参数声明之外的任何声明的修饰符.

If an @Target meta-annotation is not present on an annotation type T , then an annotation of type T may be written as a modifier for any declaration except a type parameter declaration.

如果存在@Target元注释，则编译器将根据JLS 9.7.4强制执行ElementType枚举常量指示的使用限制.

If an @Target meta-annotation is present, the compiler will enforce the usage restrictions indicated by ElementType enum constants, in line with JLS 9.7.4.

在回答您的其他问题时，我使用了:

@Target({ElementType.ANNOTATION_TYPE, ElementType.METHOD})

因为这与

Because that's the same targets used by @ParameterizedTest. I figured it was a good idea to restrict it to METHOD since the designers of @ParameterizedTest apparently feel that only methods should be directly extended by the parameterized-tests extension (see §5 Extension Model). And including ANNOTATION_TYPE allows you to place your composed annotation on another annotation, creating yet another composed annotation.

您还将看到我包含了

You'll also see I included @Documented:

如果注释类型 A 的声明中存在注释@Documented，则元素上的任何@A注释均被视为该元素的公共合同的一部分.更详细地讲，当注释类型 A 用Documented注释时，类型 A 的注释的存在和值是公共合同的一部分. A 元素的注释.相反，如果注释类型 B 没有用Documented注释，则 B 注释的存在和值不属于元素公共合同的一部分. B 进行注释.具体来说，如果注释类型用Documented注释，则默认情况下，像javadoc这样的工具将在其输出中显示该类型的注释，而不会显示不包含Documented的注释类型的注释.

If the annotation @Documented is present on the declaration of an annotation type A, then any @A annotation on an element is considered part of the element's public contract. In more detail, when an annotation type A is annotated with Documented, the presence and value of annotations of type A are a part of the public contract of the elements A annotates. Conversely, if an annotation type B is not annotated with Documented, the presence and value of B annotations are not part of the public contract of the elements B annotates. Concretely, if an annotation type is annotated with Documented, by default a tool like javadoc will display annotations of that type in its output while annotations of annotation types without Documented will not be displayed.

请注意，这些注释(@Retention，@Target和@Documented)并非特定于JUnit.这些注释是Java中注释如何工作的基础，并且每个注释都驻留在java.lang.annotation程序包中.

Notice that theses annotations—@Retention, @Target, and @Documented—are not specific to JUnit. These annotations are fundamental to how annotations in Java work and each one resides in the java.lang.annotation package.

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