Spring是否支持为每个@Test测试方法加载不同的application.properties文件？

针对你需要为每个测试方法单独修改配置属性的需求，有两种无需单独创建测试类的实现方式：

方案1：方法级@TestPropertySource（推荐，Spring Boot 2.2+ 支持） #

Spring Framework 5.2 及对应配套的 Spring Boot 2.2+ 版本开始，@TestPropertySource 注解支持直接标注在测试方法上，可直接指定要修改的单个属性值，完全匹配你的需求。
修改后的测试代码示例：

@RunWith(SpringRunner.class)
@SpringBootTest
public class ProtocolBeansTest
{

    @Autowired
    private ApplicationContext applicationContext;

    @Test
    @TestPropertySource(properties = "PROTOCOL_DATA_TYPE = tcp")
    public void test1()
    {
        Assert.assertThrows(NoSuchBeanDefinitionException.class,
                            () -> applicationContext.getBean(KafkaTopicConfig.class));
        Assert.assertThrows(NoSuchBeanDefinitionException.class, () -> applicationContext.getBean(Producer.class));
        Assert.assertThrows(NoSuchBeanDefinitionException.class, () -> applicationContext.getBean(Consumer.class));
        Assert.assertNotNull(applicationContext.getBean(TcpConfig.class));
        Assert.assertNotNull(applicationContext.getBean(MyController.class));
        Assert.assertNotNull(applicationContext.getBean(ScheduledTasks.class));
    }

    @Test
    @TestPropertySource(properties = "PROTOCOL_DATA_TYPE = kafka")
    public void testKafkaBeansAreOnOthersAreOff()
    {
        Assert.assertThrows(NoSuchBeanDefinitionException.class, () -> applicationContext.getBean(TcpConfig.class));
        Assert.assertThrows(NoSuchBeanDefinitionException.class,
                            () -> applicationContext.getBean(KokosProtoController.class));
        Assert.assertThrows(NoSuchBeanDefinitionException.class,
                            () -> applicationContext.getBean(ScheduledTasks.class));
        Assert.assertNotNull(applicationContext.getBean(KafkaTopicConfig.class));
        Assert.assertNotNull(applicationContext.getBean(Producer.class));
        Assert.assertNotNull(applicationContext.getBean(Consumer.class));
    }

    @Test
    @TestPropertySource(properties = "PROTOCOL_DATA_TYPE = none")
    public void test3()
    {
        Assert.assertThrows(NoSuchBeanDefinitionException.class, () -> applicationContext.getBean(TcpConfig.class));
        Assert.assertThrows(NoSuchBeanDefinitionException.class,
                            () -> applicationContext.getBean(KokosProtoController.class));
        Assert.assertThrows(NoSuchBeanDefinitionException.class,
                            () -> applicationContext.getBean(ScheduledTasks.class));
        Assert.assertThrows(NoSuchBeanDefinitionException.class,
                            () -> applicationContext.getBean(KafkaTopicConfig.class));
        Assert.assertThrows(NoSuchBeanDefinitionException.class, () -> applicationContext.getBean(Producer.class));
        Assert.assertThrows(NoSuchBeanDefinitionException.class, () -> applicationContext.getBean(Consumer.class));
    }

    @TestConfiguration
    @ConditionalOnProperty(value = PROTOCOL_DATA_TYPE,
                           havingValue = KAFKA_PROTOCOL_TYPE)
    public static class SomeServiceMockConfig
    {

        @MockBean
        private static KafkaTopicConfig kafkaTopicConfig;

    }

}

方案2：嵌套测试类（兼容低版本Spring Boot） #

如果你的Spring Boot版本低于2.2，不支持方法级@TestPropertySource，可以用JUnit的@Nested注解创建嵌套测试类，每个嵌套类对应一套配置，所有测试都在同一个外层类中，无需创建独立测试文件。
代码示例：

@RunWith(SpringRunner.class)
@SpringBootTest
public class ProtocolBeansTest
{
    @Nested
    @TestPropertySource(properties = "PROTOCOL_DATA_TYPE = tcp")
    class TcpProtocolTest {
        @Autowired
        private ApplicationContext applicationContext;
        
        @Test
        public void test1()
        {
            // 原test1逻辑不变
        }
    }

    @Nested
    @TestPropertySource(properties = "PROTOCOL_DATA_TYPE = kafka")
    class KafkaProtocolTest {
        @Autowired
        private ApplicationContext applicationContext;
        
        @Test
        public void testKafkaBeansAreOnOthersAreOff()
        {
            // 原kafka测试逻辑不变
        }
    }

    @Nested
    @TestPropertySource(properties = "PROTOCOL_DATA_TYPE = none")
    class NoneProtocolTest {
        @Autowired
        private ApplicationContext applicationContext;
        
        @Test
        public void test3()
        {
            // 原test3逻辑不变
        }
    }

    @TestConfiguration
    @ConditionalOnProperty(value = PROTOCOL_DATA_TYPE,
                           havingValue = KAFKA_PROTOCOL_TYPE)
    public static class SomeServiceMockConfig
    {
        @MockBean
        private static KafkaTopicConfig kafkaTopicConfig;
    }
}

注意事项 #

• 两种方案都会为每个测试方法/嵌套类单独初始化Spring上下文，可添加@DirtiesContext(classMode = DirtiesContext.ClassMode.AFTER_EACH_TEST_METHOD) 注解及时清理上下文，避免不同测试间的配置互相干扰。
• 以上两种方式都无需修改原业务配置逻辑，仅通过测试层注解即可实现单属性的自定义修改。

内容的提问来源于stack exchange，提问作者Mica Straus