Dagger2 + Mockito: How to Unit Test this scenario?

Question

I'm working on a team project which has a very coupled code. I'm trying to increase the unit test coverage and I've faced the following scenario:

class Foo {
    static void methodA () {
        Bar b = new Bar();
        b.getContent();
    }
}

class Bar {

    @Inject
    DBAcessor mDBAcessor;

    Bar () {
        Dagger2.getInjector().inject(this);
    }

    public Object getContent() {
        mDBAcessor.fetchData();
    }

}

I want to unit test methodA() , however I don't know if it is possible to do it without passing the DBAcessor object via constructor to Bar() class. Bar should be a POJO model being widely used throughout the project, hence, I don't know if it would be a good idea to change its constructor and impact so many other classes. Any tips on how should I approach this scenario?

Answer 1

That is wrong design.

Whenever you have an access to the constructor, pass class dependencies into constructor. That really eases unit testing. Class Bar should look:

class Bar() {

    @Inject DBAcessor mDBAcessor;

    Bar (DBAcessor dbAcessor) {
        this.mDBAcessor = dbAcessor;
    }

    public Object getContent() {
        mDBAcessor.fetchData();
    }
}

Dagger2 methods declared in Component should only be used inside object you don't have an access to the constructor ( Activity or Fragment ).

Then nothing prevents you from doing that:

DBAccessor dbAccessor = Mockito.mock(DBAccessor.class);
Bar bar = new Bar(dbAccessor);
bar.getContent();
verify(bar, times(1)).fetchData();

If you really need to stick to such design, then you can't make unit tests on such object, as Dagger2 depends on Application object, which needs Context , which you cannot emulate in unit tests. Write your test as androidTest , create appropriate Activity , fetch Bar object from it and test it.