C# Unit Testing in C# Test Driven Development TDD

Lone Nielsen
Lone Nielsen
13,764 Points

need help.. Can't find a solution

Implement the Subtract method so that the test passes.

Calculator.cs
public class Calculator
{
    public double Result;

    public Calculator(double number)
    {
        Result = number;
    }     

    public void Add(double number)
    {
        Result += number;
    }

    public void Substract(double number)
    {
        Result -= number;
    }
}
CalculatorTests.cs
using Xunit;

public class CalculatorTests
{
    [Fact]
    public void Initialization()
    {
        var expected = 1.1;
        var target = new Calculator(1.1);
        Assert.Equal(expected, target.Result, 1);
    }

    [Fact]
    public void BasicAdd()
    {
        var target = new Calculator(1.1);
        target.Add(2.2);
        var expected = 3.3;
        Assert.Equal(expected, target.Result, 1);
    }

    [Fact]
    public void BasicSubtract()
    {
        var target = new Calculator(1.1);
        target.Subtract(0.2);
        var expected = 0.9;
        Assert.Equal(expected, target.Result, 1);
    }
}

2 Answers

Steven Parker
Steven Parker
203,138 Points

You're really close, but you you have a little spelling/typo error.

You have "Substract" (with an extra "s") instead of "Subtract".

Carel Du Plessis
PRO
Carel Du Plessis
Pro Student 16,356 Points

Can someone please explain what the last parameter (1) does in this piece of code Assert.Equal(expected, target.Result, 1);.

I have looked at the documentation and found only two object passed in as the parameter.

https://docs.microsoft.com/en-us/dotnet/api/microsoft.visualstudio.testtools.unittesting.assert.equals?view=mstest-net-1.2.0