java - 如何在 JUnit 4.12 中组合 @Rule 和 @ClassRule

Question

根据 the 4.12 release notes , 可以同时使用@Rule 和@ClassRule 注释测试类的静态成员:

a static member annotated with both @Rule and @ClassRule is now considered valid. This means a single rule may be used to perform actions both before/after a class (e.g. setup/tear down an external resource) and between tests (e.g. reset the external resource),

我想使用此功能在文件中的所有测试开始时初始化资源，在每次测试之间对资源进行一些清理，并在所有测试完成后处理它。此资源当前由扩展 ExternalResource 的类表示.

在我的before 和after 方法中，如何区分“所有测试之前/之后”和“每次测试之前/之后”？我是否需要使用 TestRule 的不同/自定义实现来完成此操作？

Answer 1

你可以实现TestRule#apply并使用 isTest和 isSuite Description 的方法确定什么样的Statement你的TestRule正在应用于。

这是一个示例界面，您可以构建该界面以提供具有完整 before 的规则, after , verify , beforeClass , afterClass , verifyClass类型行为:

public interface CombinedRule extends TestRule {
    default Statement apply(Statement base, Description description) {
        if (description.isTest()) {
            return new Statement() {
                public void evaluate() throws Throwable {
                    before();
                    try {
                        base.evaluate();
                        verify();
                    } finally {
                        after();
                    }
                }
            };
        }
        if (description.isSuite()) {
            return new Statement() {
                public void evaluate() throws Throwable {
                    beforeClass();
                    try {
                        base.evaluate();
                        verifyClass();
                    } finally {
                        afterClass();
                    }
                }
            };
        }
        return base;
    }

    default void before() throws Exception {
        //let the implementer decide whether this method is useful to implement
    }

    default void after() {
        //let the implementer decide whether this method is useful to implement
    }

    /**
     * Only runs for Tests that pass
     */
    default void verify() {
        //let the implementer decide whether this method is useful to implement
    }

    default void beforeClass() throws Exception {
        before();
    }

    default void afterClass() {
        after();
    }

    /**
     * Only runs for Suites that pass
     */
    default void verifyClass() {
        verify();
    }
}