Calculator { public double mul(double firstOperand, double secondOperand) { return firstOperand * secondOperand; }  double add(double firstOperand, double secondOperand); double sub(double firstOperand, double secondOperand); double div(double firstOperand, double secondOperand); double mul(double firstOperand, double secondOperand); double pow(double firstOperand, double secondOperand);  }
@Test public void mulTwoNumbers() { double resultMul = mCalculator.mul(32d, 2d); assertThat(resultMul, is(equalTo(64d))); }
@Test public void mulTwoNumbers() { double resultMul = mCalculator.mul(2d, 2d); assertThat(resultMul, is(equalTo(4d))); }
@Test public void mulTwoNumbersZero() { double resultMul = mCalculator.mul(2d, 0d); assertThat(resultMul, is(equalTo(0d))); }