java - solo.finishOpenActivities() は常に null

Question

私はテストクラスを持っていますが、常にNullPointerExceptioninを取得しtearDown()ます。誰かが理由を知っていますか?

public class LaunchManagerActivityTest extends ActivityInstrumentationTestCase2<LaunchManagerActivity> {

    private Solo solo;

    public LaunchManagerActivityTest() {
        super(LaunchManagerActivity.class);
    }

    @Override
    protected void setUp() throws Exception {
        super.setUp();

        solo = new Solo(getInstrumentation(), getActivity());
    }

    @Override
    protected void tearDown() throws Exception {
        super.tearDown();
        solo.finishOpenedActivities();
    }

    public void testOne() {

    }

    public void testTwo() {

    }