Junit Test an Activity getting null pointer exceotion

Question

public class FitiquityTest extends ActivityInstrumentationTestCase2<LoginActivity> {
    LoginActivity mActivity;
    private EditText username;
    private EditText password;
    public FitiquityTest()
    {
        super("com.packagename.LoginActivity",LoginActivity.class);
    }

    @Override
    protected void setUp() throws Exception {
        super.setUp();
        mActivity = this.getActivity();
        username = (EditText) mActivity.findViewById(R.id.login_email_mobile_et);
        password = (EditText) mActivity.findViewById(R.id.login_password_et);
    }

    @Test
    public void testPreconditions() {
        assertNotNull(username);
        assertNotNull(password);
    }

    @Test
    public void testText() {
        assertEquals("hello",username.getText());
        assertEquals("hello123", password.getText());
    }

}

This is my Test class.I am trying to learn junit.I have an activity named login.I want to test on it.Now in the above class I am getting exception on setup method in mActivity = this.getActivity(); line.So my question is if I am not be able to start an activity so I will get a null pointer exception obviously.So how to start an Activity in junit test class.I have tried the following link answer 2 also.

Android - AssertionFailedError on startActivity method in ActivityUnitTestCase test class

//Now please help as I am new to Junit.

//I have added instrumentation tag in Manifest also.Lint is also disabaled.

<instrumentation
    android:targetPackage="com.fitiquity"
    android:name="android.test.InstrumentationTestRunner" />

    <uses-library android:name="android.test.runner" />