@Test
    public void addTwoNumbers() {
        double resultAdd = mCalculator.add(1d, 1d);
        assertThat(resultAdd).isEqualTo(2d);
    }
JUnit4 unit tests for the calculator logic.
runner/AndroidJunitRunnerSample/app/src/androidTest/java/com/example/android/testing/androidjunitrunnersample/CalculatorTest.java