具有自动装配依赖项的模拟服务 class

Question

I have a Service class & a config class as below:

public class MyService{

 @Autowired
 MyConfig myconfig;

 @Autowired
 private WebClient webClient;

 private String result;

 public String fetchResult(){
   return webClient.get().uri(myConfig.getUrl()).retrieve().bodyToMono(String.class).block();
 }
}

@ConfigurationProperties("prefix="somefield")
@Component
class MyConfig{
   private String url;
   //getter & setter
  }
}

Below is the Junit:

@Runwith(MockitoJUnitRunner.class)
public class TestMe{

    @InjectMocks
    MyService myService;

    @Test
    public void myTest(){
       when(myService.fetchResult().then return("dummy");
    }
}

I am getting null pointer error when I run this class at webClient in Service class. What could be the issue. I am new to JUnits. How do I write a proper JUnit for this.

Answer 1

The easiest way to make the class testable is to use constructor injection

public class MyService{
  private final MyConfig myconfig;
  private final WebClient webClient;
  private String result;

  @AutoWired
  MyService(
    MyConfig myconfig,
    WebClient webClient
  ) {
    this.myconfig = myconfig;
    this.webClient = webClient;
  }

  ...
}