Question

I have the following situation:

class Worker {  
  public Integer somework() {  
      Integer k=0;  
      Helper h= new Helper();  
      h.change(k);  
      return k;  
    }
}

class Helper {
  public void change(Integer k) {
    //k = Some calcs
  }
}

I’m making unitests for Worker and obviously I want to mock Helper class so that his change method will always put 1 into k.

My real situation is more complicated but this code represents the issue. Thanks for help.

Answer 1

I would change the method signature and make it take a Helper instance as argument. The caller would create the helper and pass it to the somework method. The test would pass a mock helper.

If this isn’t possible, at least call a protected factory method to create the helper, and mock this factory method when testing the somework method in order to make it return a mock helper:

class Worker {  
    public Integer somework(){  
        Integer k=0;  
        Helper h= createHelper();  
        h.change(k);  
        return k;  
    }

    // this method may be mocked when testing somework, to return a mock helper.
    protected Helper createHelper() {
        return new Helper();
    }
}