How can I test this method using Mockito?

Question

I have a method with complex interaction between different objects that I would like to test using the Mockito framework. I would appreciate some guidelines. I know the code does not mean much.

Both getInstance() methods are static. I would like to mock obj3 and make the if statement to return true in the test.

public MyRequest getRequest(ObjectOne obj1, ObjectTwo obj2) {

    ObjectThree obj3 = FactoryOne.getInstance().getList().getObject(obj2.getId());


    if(FactoryTwo.getInstance().isFlagSet("flag")){
        ....
    }


    return new MyRequest(....);
}

Answer 1

Actually, the method invoked to value the obj3 variable is not straight testable.

The root cause is getInstance() that is a static method.

In fact, FactoryOne.getInstance() should be a dependency of the class under test and the returned object should be an interface

In this way, you can define a constructor that sets the dependency:

public MyClass(FooInterface foo){
   this.foo = foo;
}

And replace :

ObjectThree obj3 = FactoryOne.getInstance().getList().getObject(obj2.getId());

by :

ObjectThree obj3 = foo.getList().getObject(obj2.getId());

In the application code, you could invoke the constructor :

MyClass c = new MyClass(FactoryOne.getInstance().getList());

And in the test code, you could create a mock for the Foo interface, set it to the class under the test via the constructor :

Foo fooMock = Mockito.mock(Foo.class);
MyClass myClassUnderTest = new MyClass(fooMock);

Then record a mock behavior for getList() to return another mocked object with the desired value for the invocation to getObject() in the test.