检查JUnit扩展是否引发特定异常

Question

public class DisallowUppercaseLetterAtBeginning implements BeforeEachCallback {

    @Override
    public void beforeEach(ExtensionContext context) {
        char c = context.getRequiredTestMethod().getName().charAt(0);
        if (Character.isUpperCase(c)) {
            throw new RuntimeException("test method names should start with lowercase.");
        }
    }
}

现在我想测试我的扩展是否按预期工作。

@ExtendWith(DisallowUppercaseLetterAtBeginning.class)
class MyTest {

    @Test
    void validTest() {
    }

    @Test
    void TestShouldNotBeCalled() {
        fail("test should have failed before");
    }
}

如何编写测试来验证执行第二个方法的尝试是否会引发带有特定消息的RuntimeException？

Answer 1

另一种方法是使用新的JUnit5-Jupiter框架提供的工具。

下面是我在Eclipse Oxyow上用Java1.8测试的代码。代码缺乏优雅和简洁，但希望可以作为为您的元测试用例构建健壮解决方案的基础。

请注意，这实际上是JUnit5的测试方式，我让您参考GitHub上Jupiter引擎的单元测试。

public final class DisallowUppercaseLetterAtBeginningTest { 
    @Test
    void testIt() {
        // Warning here: I checked the test container created below will
        // execute on the same thread as used for this test. We should remain
        // careful though, as the map used here is not thread-safe.
        final Map<String, TestExecutionResult> events = new HashMap<>();

        EngineExecutionListener listener = new EngineExecutionListener() {
            @Override
            public void executionFinished(TestDescriptor descriptor, TestExecutionResult result) {
                if (descriptor.isTest()) {
                    events.put(descriptor.getDisplayName(), result);
                }
                // skip class and container reports
            }

            @Override
            public void reportingEntryPublished(TestDescriptor testDescriptor, ReportEntry entry) {}
            @Override
            public void executionStarted(TestDescriptor testDescriptor) {}
            @Override
            public void executionSkipped(TestDescriptor testDescriptor, String reason) {}
            @Override
            public void dynamicTestRegistered(TestDescriptor testDescriptor) {}
        };

        // Build our test container and use Jupiter fluent API to launch our test. The following static imports are assumed:
        //
        // import static org.junit.platform.engine.discovery.DiscoverySelectors.selectClass
        // import static org.junit.platform.launcher.core.LauncherDiscoveryRequestBuilder.request

        JupiterTestEngine engine = new JupiterTestEngine();
        LauncherDiscoveryRequest request = request().selectors(selectClass(MyTest.class)).build();
        TestDescriptor td = engine.discover(request, UniqueId.forEngine(engine.getId())); 

        engine.execute(new ExecutionRequest(td, listener, request.getConfigurationParameters()));

        // Bunch of verbose assertions, should be refactored and simplified in real code.
        assertEquals(new HashSet<>(asList("validTest()", "TestShouldNotBeCalled()")), events.keySet());
        assertEquals(Status.SUCCESSFUL, events.get("validTest()").getStatus());
        assertEquals(Status.FAILED, events.get("TestShouldNotBeCalled()").getStatus());

        Throwable t = events.get("TestShouldNotBeCalled()").getThrowable().get();
        assertEquals(RuntimeException.class, t.getClass());
        assertEquals("test method names should start with lowercase.", t.getMessage());
}