Mockito with local variables

Question

I have a simple method that returns a String.

It also creates a local List. I want to test the value added to the local List.

Here is an example

package com.impl;

import java.util.ArrayList;
import java.util.List;

import com.test.domain.CustomerVo;

public class ClassImpl {

    public String assignGift(CustomerVo customerVo) {
        List<String> listOfGift = new ArrayList<String>();

        if (customerVo.getName().equals("Joe")) {
            listOfGift.add("ball");
        } else if ((customerVo.getName().equals("Terry"))) {
            listOfGift.add("car");
        } else if (customerVo.getName().equals("Merry")) {
            listOfGift.add("tv");
        }else {
            listOfGift.add("no gift");
        }

        return "dummyString";
    }
}

How can I test that when the customerVo.getName.equals("Terry"), car is added to the local List.

Answer 1

This isn't altogether that easy.

You need to use something like powermock.

With powermock you create create a scenario before then method is called and play it back, this means you can tell the ArrayList class constructor to anticipate being called and return a mock rather than a real ArrayList.

This would allow you to assert on the mock.

Something like this ought to work:

ArrayList listMock = createMock(ArrayList.class);
expectNew(ArrayList.class).andReturn(listMock);

So when your method creates the local List powermock will actually return your mock List.

More information here.

This sort of mocking is really for unit testing of legacy code that wasn't written to be testable. I would strongly recommend, if you can, rewriting the code so that such complex mocking doesn't need to happen.