为 JUnit 4/5 创建注释以在测试中初始化和注入对象

Question

我正在为 Kafka 开发一个测试库，Kafkaesque。该库允许您使用流畅且优雅的（？！）API 为 Kafka 开发集成测试。目前，我为 Spring Kafka 开发版本。

库需要在每次测试中初始化：

 @Test
 void consumeShouldConsumeMessagesProducesFromOutsideProducer() {
   kafkaTemplate.sendDefault(1, "data1");
   kafkaTemplate.sendDefault(2, "data2");
   new SpringKafkaesque(broker)
       .<Integer, String>consume()
       .fromTopic(CONSUMER_TEST_TOPIC)
       .waitingAtMost(1L, TimeUnit.SECONDS)
       .waitingEmptyPolls(5, 100L, TimeUnit.MILLISECONDS)
       .withDeserializers(new IntegerDeserializer(), new StringDeserializer())
       .expecting()
       .havingRecordsSize(2)
       .assertingThatPayloads(Matchers.containsInAnyOrder("data1", "data2"))
       .andCloseConsumer();
 }

我不想手动初始化SpringKafkaesque 对象，而是想创建一个对我来说具有魔力的注释。类似于 Spring Kafka 的 @EmbeddedKafka 注解。

@SpringBootTest(classes = {TestConfiguration.class})
@Kafkaesque(
    topics = {SpringKafkaesqueTest.CONSUMER_TEST_TOPIC, SpringKafkaesqueTest.PRODUCER_TEST_TOPIC})
class SpringKafkaesqueTest {
  @Autowired
  private Kafkaesque kafkaesque;

  @Test
  void consumeShouldConsumeMessagesProducesFromOutsideProducer() {
    kafkaTemplate.sendDefault(1, "data1");
    kafkaTemplate.sendDefault(2, "data2");
    kafkaesque
        .<Integer, String>consume()
        .fromTopic(CONSUMER_TEST_TOPIC)
        .waitingAtMost(1L, TimeUnit.SECONDS)
        .waitingEmptyPolls(5, 100L, TimeUnit.MILLISECONDS)
        .withDeserializers(new IntegerDeserializer(), new StringDeserializer())
        .expecting()
        .havingRecordsSize(2)
        .assertingThatPayloads(Matchers.containsInAnyOrder("data1", "data2"))
        .andCloseConsumer();
   }

有可能吗？有什么建议吗？

Answer 1

JUnit 4

一种可能的解决方案是使用反射创建自定义注释处理。可以通过@Rule获取测试方法名，例如：

public class CustomAnnotationTest {
    
    private SpringKafkaesque kafkaesqueInstance;

    @Rule
    public TestName testName = new TestName();

    @Before
    public void init() {
        Method method = null;
        try {
            method = this.getClass().getMethod(testName.getMethodName());
        } catch (Exception ex) {
            // handle exceptions
        }
        if (method.isAnnotationPresent(EmbeddedKafka.class)) {
            // Init your SpringKafkaesque instance here
            // kafkaesqueInstance = new SpringKafkaesque(broker)
            //
        }
    }

    @EmbeddedKafka
    @Test
    public void testCustomAnnotated() {
        // your test here
    }

    @Retention(RetentionPolicy.RUNTIME)
    @Target(ElementType.METHOD)
    @interface EmbeddedKafka {
    }
}

您需要将此实例存储在类级变量中。对于没有@EmbeddedKafka注解的方法，这个变量将是null。

JUnit 5

对于 JUnit 5，您可以考虑使用带有 ParameterResolver 的参数注入。首先，你需要实现这个接口：

public class KafkaesqueResolver implements ParameterResolver {
    @Override
    public boolean supportsParameter(ParameterContext parameterContext,
                                     ExtensionContext extensionContext) throws ParameterResolutionException {
        return parameterContext.getParameter().getType() == SpringKafkaesque.class;
    }

    @Override
    public Object resolveParameter(ParameterContext parameterContext,
                                   ExtensionContext extensionContext) throws ParameterResolutionException {
        // Create an instance of SpringKafkaesque here and return it
        return new SpringKafkaesque();
    }
}

接下来，在你的测试类中添加@ExtendWith(KafkaesqueResolver.class)注解，并在你的测试方法中添加一个参数，这里需要SpringKafkaesque的实例：

@ExtendWith(KafkaesqueResolver.class)
public class ParamInjectionTest {

    @Test
    public void testNoParams() {
        // nothing to inject
    }

    @Test
    public void testWithParam(SpringKafkaesque instance) {
        // do what you need with your instance
    }
}

在这种情况下不需要自定义注释。