java – 为什么组件扫描不适用于Spring Boot单元测试？

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服务类FooServiceImpl使用@Service aka @Component进行注释,这使其有资格进行自动装配.为什么在单元测试期间没有拾取和自动装配此类？

@Service
public class FooServiceImpl implements FooService {
    @Override
    public String reverse(String bar) {
        return new StringBuilder(bar).reverse().toString();
    }
}

@RunWith(SpringRunner.class)
//@SpringBootTest
public class FooServiceTest {
    @Autowired
    private FooService fooService;
    @Test
    public void reverseStringShouldReverseAnyString() {
        String reverse = fooService.reverse("hello");
        assertThat(reverse).isEqualTo("olleh");
    }
}

测试无法加载应用程序上下文,

2018-02-08T10:58:42,385 INFO    Neither @ContextConfiguration nor @ContextHierarchy found for test class [io.github.thenilesh.service.impl.FooServiceTest], using DelegatingSmartContextLoader
2018-02-08T10:58:42,393 INFO    Could not detect default resource locations for test class [io.github.thenilesh.service.impl.FooServiceTest]: no resource found for suffixes {-context.xml}.
2018-02-08T10:58:42,394 INFO    Could not detect default configuration classes for test class [io.github.thenilesh.service.impl.FooServiceTest]: FooServiceTest does not declare any static, non-private, non-final, nested classes annotated with @Configuration.
2018-02-08T10:58:42,432 INFO    Loaded default TestExecutionListener class names from location [META-INF/spring.factories]: [org.springframework.boot.test.mock.mockito.MockitoTestExecutionListener, org.springframework.boot.test.mock.mockito.ResetMocksTestExecutionListener, org.springframework.boot.test.autoconfigure.restdocs.RestDocsTestExecutionListener, (...)org.springframework.test.context.transaction.TransactionalTestExecutionListener, org.springframework.test.context.jdbc.SqlScriptsTestExecutionListener]
2018-02-08T10:58:42,448 INFO    Using TestExecutionListeners: [org.springframework.test.context.web.ServletTestExecutionListener@f0ea28, org.springframework.test.context.support.DirtiesContextBeforeModesTestExecutionListener@16efaab,(...)org.springframework.boot.test.autoconfigure.web.servlet.MockMvcPrintOnlyOnFailureTestExecutionListener@9604d9]
2018-02-08T10:58:42,521 INFO    Refreshing org.springframework.context.support.GenericApplicationContext@173f9fc: startup date [Thu Feb 08 10:58:42 IST 2018]; root of context hierarchy
2018-02-08T10:58:42,606 INFO    JSR-330 'javax.inject.Inject' annotation found and supported for autowiring
2018-02-08T10:58:42,666 ERROR    Caught exception while allowing TestExecutionListener [org.springframework.test.context.support.DependencyInjectionTestExecutionListener@19aaa5] to prepare test instance [io.github.thenilesh.service.impl.FooServiceTest@57f43]
org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'io.github.thenilesh.service.impl.FooServiceTest': Unsatisfied dependency expressed through field 'fooService'; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'io.github.thenilesh.service.FooService' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:588) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
    . . . 
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192) [.cp/:?]
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'io.github.thenilesh.service.FooService' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoMatchingBeanFound(DefaultListableBeanFactory.java:1493) ~[spring-beans-4.3.13.RELEASE.jar:4.3.13.RELEASE]
    ... 28 more
2018-02-08T10:58:42,698 INFO    Closing org.springframework.context.support.GenericApplicationContext@173f9fc: startup date [Thu Feb 08 10:58:42 IST 2018]; root of context hierarchy

Full stack trace

如果测试类用@SpringBootTest注释,那么它会创建整个应用程序上下文,包括数据库连接和许多不相关的bean,这显然不需要进行单元测试(那时它不会进行单元测试！).预期的是,除了使用@MockBean进行模拟之外,只应实例化FooService所依赖的bean.

解决方法:

你应该使用@SpringBootTest(classes = FooServiceImpl.class).

正如它在Annotation Type SpringBootTest提到的那样：

public abstract Class[] classes

The annotated classes to use for loading an ApplicationContext. Can
also be specified using @ContextConfiguration(classes=…). If no
explicit classes are defined the test will look for nested
@Configuration classes, before falling back to a
SpringBootConfiguration search.

Returns:
the annotated classes used to load the application context See Also:
ContextConfiguration.classes()

Default:
{}

这只会加载必要的类.如果不指定,它可能会加载数据库配置和其他会使您的测试更慢的东西.

另一方面,如果你真的想要单元测试,你可以在没有Spring的情况下测试这段代码 – 然后@RunWith(SpringRunner.class)和@SpringBootTest注释是没有必要的.您可以测试FooServiceImpl实例.如果您有自动装配/注入的属性或服务,则可以通过setter,构造函数或使用Mockito模拟它们.

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