如何为手动依赖注入创建mockito测试

Question

I am creating manual dependency injection using java. I am trying to create Mockito test for the same.

As I am new to Mockito and I have done only for framework based before. So need your help on the below

//All Business logic holder class. It does not have any new operator. Even, it does not have any knowledge about the concrete implementations
class MyClass {

private MyProto a;
private B b;
private C c;

MyClass(MyProtoImpl a, B b, C c) {
 //Only Assignment
 this.a = a;
 this.b = b;
 this.c = c;
}

//Application Logic
public void doSomething() {
 a.startClient(c);
 //Do B specific thing
 //Do C specific thing
 }
}

//The Factory. All the new operators should be placed in this factory class and wiring related objects here.
class MyFactory {
 public MyClass createMyClass() {
   return new MyClass(new AImpl(), new BImpl(), new CImpl());
  }
}

class Main {
 public static void main(String args[]) {
  MyClass mc = new MyFactory().createMyClass();
  mc.doSomething();
 }
}

So at last I need to achieve two things.

1. To Test MyFactory class and MyClass
2. To Test MyProtoImpl class. So in this way I can get the entire codecoverage. So not only MyProtoImpl need to be covered with Junit Mockito MyFactory and MyClass also need to be covered

Answer 1

Normally you want to create mocks of your dependencies. From the comments it seems that you want to test the classes in separation, hence I would suggest "unit testing" the modules. I will walk you through the testing of MyClass .

class MyTestClass {

    // First you want to create mocks of your dependencies
    @Mock
    MyProto a;

    @Mock
    B b;

    @Mock
    C c;

    // At this point Mockito creates mocks of your classes.
    // Calling any method on the mocks (c.doSomething()) would return null if the
    // method had a return type.

    @Test
    void myFirstTest(){
     // 1. Configure mocks for the tests
     // here you configure the mock's returned values (if there are any).
     given(a.someMethod()).willReturn(false);

     // 2. Create the SUT (Software Under Test) Here you manually create the class
     // using the mocks.
     MyClass myClass = new MyClass(a, b, c);

     // 3. Do the test on the service
     // I have assumed that myClass's doSomething simply returns a.someMethod()'s returned value
     boolean result = myClass.doSomething();

     // 4. Assert
     assertTrue(result);
     // Alternatively you can simply do:
     assertTrue(myClass.doSomething());
    }
}

If your classes contain void methods, you can test whether the methods have been called with the correct arguments:

     verify(a).someMethod(someParameter);

That's pretty much it for Mockito. You create mocks, you set the desired behavior, and finally you assert the result or verify that the methods have been called with the correct arguments.

However I don't think it makes that much sense to "Mockito-test" classes that are responsible for database connections and similar configuration. Mockito testing is IMHO more suited to test the service/logic layer of the application. If you had a spring project I would simply test such configuration classes (ie database config etc.) in a scenario, where i establish a real connection to the database.