@Test public void addTwoNumbersWorksWithNegativeResult() { double resultAdd = mCalculator.add(-1d, -17d); assertThat(resultAdd, is(equalTo(-18d))); }
public double add(double firstOperand, double secondOperand) { return firstOperand + secondOperand; }
Calculator { public double add(double firstOperand, double secondOperand) { return firstOperand + secondOperand; } }
Calculator { public double add(double firstOperand, double secondOperand) { return firstOperand + secondOperand; }  }
Calculator { public double add(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); }
Calculator { public double add(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);  }