@Test(timeout = 1000)
 public void testSquareRoot() {
   calculator.squareRoot(4);
   assertEquals(2, calculator.getResult());
 }
 @Test
 public void testSubstract() {
   calculator.add(10);
   calculator.substract(2);
   assertEquals(8, calculator.getResult());
 }
 @Test
 public void testDivide() {
   calculator.add(8);
   calculator.divide(2);
   assertEquals(4, calculator.getResult());
 }
 @Test
 public void testAdd() {
   calculator.add(2);
   calculator.add(3);
   assertEquals(5, calculator.getResult());
 }