Instrumented Unit Class Test - Can't create handler inside thread that has not called Looper.prepare()

Sorry I've looked at tutorials all over the place and not found the answer I'm looking for. I'm following Google's Tutorial at the moment here: http://ift.tt/1L3U2Cy

I'm trying to create an Instrumented test and when I run it I'm getting the error : java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()

So my test is as follows:

    package testapp.silencertestapp;

import android.support.test.filters.SmallTest;
import android.support.test.runner.AndroidJUnit4;

import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;

import static org.hamcrest.Matchers.is;
import static org.junit.Assert.assertThat;

@RunWith(AndroidJUnit4.class)
@SmallTest
public class MainActivityTest {

    private MainActivity testMain;

    @Before
    public void createActivity(){
        testMain = new MainActivity();
    }

    @Test
    public void checkFancyStuff(){
        String time = testMain.createFancyTime(735);

        assertThat(time, is("07:35"));
    }
}

And I'm trying to run a method inside the main activity is as follows (this is an extract):

public class MainActivity extends AppCompatActivity {

    private TimePicker start;
    private TimePicker end;

@Override
    protected void onCreate(Bundle savedInstanceState) {
        start = (TimePicker) findViewById(R.id.startPicker);
        end = (TimePicker) findViewById(R.id.endPicker);
}

 String createFancyTime(int combinedTime) {

        StringBuilder tempString = new StringBuilder(Integer.toString(combinedTime));
        if(tempString.length()==4){
            tempString = tempString.insert(2, ":");
        }
        else if (tempString.length()==3){
            tempString = tempString.insert(1, ":");
            tempString = tempString.insert(0, "0");
        }
        else if(tempString.length()==2){
            tempString = tempString.insert(0, "00:");
        }
        else if(tempString.length()==1){
            tempString = tempString.insert(0, "00:0");
        }
        return tempString.toString();
    }

I presume that this is an issue because I'm not starting the service up correctly or something - I've tried using several ways, but I just get errors everywhere. Searching on here and this error is popular, but not in relation to testing, so wondered if anyone could kindly point me in the right direction so I can test the methods in this class?