Exercise: Kill all the mutants!

It's time for you to add the missing test cases and even modify your existing code to kill all the remaining surviving mutants.

You will find the solution for this exercise below but I highly encourage you to take your time and try to solve the problem on your own.

Expand me if you want to see the solution

CalculatorTests.cs

public class CalculatorTests
{
    [Theory]
    [InlineData(5, 5, 10)]
    public void Test_Add(int first, int second, int expected)
    {
        // Arrange
        var sut = new Calculator();

        // Act
        var result = sut.Add(first, second);

        // Assert
        result.Should().Be(expected);
    }

    [Theory]
    [InlineData(5, 5, 0)]
    [InlineData(10, 9, 1)]
    public void Test_Subtract(int first, int second, int expected)
    {
        // Arrange
        var sut = new Calculator();
        
        // Act
        var result = sut.Subtract(first, second);

        // Assert
        result.Should().Be(expected);
    }

    [Theory]
    [InlineData(1, 1, 1)]
    [InlineData(2, 3, 6)]
    public void Test_Multiply(int first, int second, int expected)
    {
        // Arrange
        var sut = new Calculator();
        
        // Act
        var result = sut.Multiply(first, second);

        // Assert
        result.Should().Be(expected);
    }

    [Theory]
    [InlineData(1, 1, 1, 0)]
    [InlineData(4, 2, 2, 0)]
    [InlineData(5, 2, 2, 1)]
    public void Test_Divide(int first, int second, int expected, int remainder)
    {
        // Arrange
        var sut = new Calculator();
        
        // Act
        var result = sut.Divide(first, second);

        // Assert
        result.Result.Should().Be(expected);
        result.Remainder.Should().Be(remainder);
    }

    [Fact]
    public void Test_Divide_ByZero()
    {
        // Arrange
        var sut = new Calculator();

        // Act
        var result = () => sut.Divide(1, 0);
        
        // Assert
        result.Should().Throw<DivideByZeroException>();
    }
}

Calculator.cs

public class Calculator
{
    public int Add(int first, int second)
    {
        return first + second;
    }

    public int Subtract(int first, int second)
    {
        return first - second;
    }

    public int Multiply(int first, int second)
    {
        return first * second;
    }

    public (int Result, int Remainder) Divide(int first, int second)
    {
        var result = first / second;
        var remainder = first % second;
        return (result, remainder);
    }
}