当存在来自超类的依赖注入时，如何设置测试？

Question

My code is setup like this.

abstract class BaseController {
   @Inject Store store; 
}

class MyController extends BaseController {
   private final Validator validator;

   @Inject
   public MyController(Validator validator) {
      this.validator = validator;
   }

   public boolean someMethod() {
      a = store.storingMethod();
      b = validator.validate(a);
      ...
      ...
      return true;
   }
}

Now I wanted to write tests for myController . In the test, I want to use the injected Store but I want to mock out the Validator . I tried something like this.

@RunWith(MockitoJUnitRunner.class)
public class MyControllerTest() {
   private MyController myController;
   @Mock private Validator validator;

   @Before
   public void before() {
      myController = new MyController(validator);
   }
}

I know, if I move the Store store from the BaseController to MyController , I can initialize it in the constructor (just like I did for the validator). But, I want to have the Store in the Base class as it will be used by other classes extending it.

With the way my classes are set up, How do I inject the Store while testing?

Answer 1

Don't use field injection. Use constructor injection.

abstract class BaseController {
    final Store store; 

    BaseController(Store store) {
        this.store = store;
    }
}

class MyController extends BaseController {
   private final Validator validator;

   @Inject
   public MyController(Validator validator, Store store) {
      super(store);
      this.validator = validator;
   }
}

There is a bit of debate on the subject, but your example is a clear example of a situation in which the use of field injection makes a class much harder to test.

Spring @Autowire on Properties vs Constructor

Dependency Injection: Field Injection vs Constructor Injection?

It is also worth noting that

The Spring team generally advocates constructor injection

Source

Answer 2

I usually solve this using the following pattern:

abstract class BaseController {
    private final Store store; 

    protected BaseController (Store store) {
        this.store = store;
    }

    protected Store getStore() {
        return this.store;
    }
}

class MyController extends BaseController {
    private final Validator validator;

    @Inject
    public MyController(Store store, Validator validator) {
       super(store);
       this.validator = validator;
    }

    public boolean someMethod() {
        a = getStore().storingMethod();
        b = validator.validate(a);
        ...
        ...
        return true;
    }
}

So the base class can be used regardless of any injection framework available.

Answer 3

You can use ReflectionTestUtils to set your field value.

Import it in your pom.xml :

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context</artifactId>
    <version>5.1.2.RELEASE</version>
</dependency>

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-test</artifactId>
    <version>5.1.2.RELEASE</version>
    <scope>test</scope>
</dependency>

Use it to set your store:

@RunWith(MockitoJUnitRunner.class)
public class MyControllerTest() {
   private MyController myController;
   @Mock private Validator validator;

   @Before
   public void before() {
      myController = new MyController(validator);
      ReflectionTestUtils.setField(myController, "store", new YourTestStore());

      // more testing
   }
}

More info on that @ https://www.baeldung.com/spring-reflection-test-utils

Also, note that I do not think this is best practice.