Testing Expected Exceptions ActivityInstrumentationTestCase2

I want to Unit Test this simple activity :

public class MainActivity extends Activity implements OnClickListener {

    private EditText edtValue1;
    private EditText edtValue2;
    private TextView txtResult;
    private Button btnAdd;
    private Button btnMuliply;

    private ICalculator calculator;

    final String LOG_TAG = "MainScreen";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        edtValue1 = (EditText) findViewById(R.id.value1);
        edtValue2 = (EditText) findViewById(R.id.value2);
        txtResult = (TextView) findViewById(R.id.result);
        btnAdd = (Button) findViewById(R.id.addValues);
        btnMuliply = (Button) findViewById(R.id.multiplyValues);

        btnAdd.setOnClickListener(this);
        btnMuliply.setOnClickListener(this);

        calculator = new Calculator();
    }

    @Override
    public void onClick(View v) {

        int val1 = 0;
        int val2 = 0;

        try {
            val1 = Integer.parseInt(edtValue1.getText().toString());
            val2 = Integer.parseInt(edtValue2.getText().toString());
        } 
        catch (NumberFormatException exc) {
            Log.e(LOG_TAG, exc.getMessage(), exc);
            throw exc;
        }

        switch (v.getId()) {

        case R.id.addValues:
            txtResult.setText(calculator.addNumbers(val1, val2).toString());
            break;

        case R.id.multiplyValues:
            txtResult.setText(calculator.multiplyNumbers(val1, val2).toString());
            break;
        }

    }
}

The facade looks like this :

Here is the simple JUnit Test Case (Please focus on the testAddDecimalValues_NumberFormatException() method):

public class MainActivityTest extends
        ActivityInstrumentationTestCase2<MainActivity> {

    MainActivity mainActivity;
    private TextView txtResult;


    public MainActivityTest() {
        super(MainActivity.class);
    }

    @Before
    public void setUp() throws Exception {
        mainActivity = getActivity();
        txtResult = (TextView) mainActivity.findViewById(R.id.result);
    }

    private final static String NUMBER_24 = "2 4 ENTER ";
    private final static String NUMBER_74 = "7 4 ENTER ";
    private final static String ADD_RESULT = "98";


    @After
    protected void tearDown() throws Exception {

    }

    @Test
    public void testAddValues() {
        sendKeys(NUMBER_24 + NUMBER_74 + "ENTER");

        // get result
        String mathResult = txtResult.getText().toString();
        assertTrue("Add result should be 98", mathResult.equals(ADD_RESULT));
    }



    private final static String NUMBER_5_DOT_5 = "5 PERIOD 5 ENTER ";

    @Test(expected = NumberFormatException.class)
    public void testAddDecimalValues_NumberFormatException() {
            sendKeys(NUMBER_5_DOT_5 + NUMBER_74 + "ENTER");
    }

}

When I launch Unit Test testAddValues() works perfectly but testAddDecimalValues_NumberFormatException() method doesn't take into account the expected = IllegalArgumentException.class and testAddDecimalValues_NumberFormatException() test failed...

Here is the Logcat :

[2015-05-27 12:52:42 - SimpleCalcTest] Launching instrumentation android.test.InstrumentationTestRunner on 0123456789ABCDEF
[2015-05-27 12:52:42 - SimpleCalcTest] Test run failed: Instrumentation run failed due to 'Process crashed.'
[2015-05-27 12:52:42 - SimpleCalcTest] Test run finished
[2015-05-27 12:52:43 - SimpleCalcTest] Sending test information to Eclipse
[2015-05-27 12:52:44 - SimpleCalcTest] Test run failed: Instrumentation run failed due to 'java.lang.NumberFormatException'
[2015-05-27 12:52:44 - SimpleCalcTest] Test run finished

The question is : do you know how I could test an expected exception with ActivityInstrumentationTestCase2 functionnalities ?

Thank you so much.

PS : I tried differents approach from http://ift.tt/MhlwxD but I have got the same result