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C# Unit Testing in C# Test Driven Development TDD

Posted by Kevin Ruddock
Kevin Ruddock
18,323 Points

What method or operation is not implemented?

The objective: Stub out the Calculator class so that the code compiles, but the test cases in CalculatorTests fail as expected.

The error: The method or operation is not implemented.

Calculator.cs 
using System;

public class Calculator
{
    public Calculator(double val)
    {
        throw new NotImplementedException();
    }

    public double Result{get;set;}

    public void Add(double val)
    {
        throw new NotImplementedException();
    }
}
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);
    }
}

3 Answers

Steven Parker
Steven Parker
231,521 Points
Steven Parker
Steven Parker
231,521 Points

Here, you want them to be "implemented".

For the purposes of testing, you want the functions implemented but empty. Don't throw the exceptions, that's essentially the same as not having the function at all.

Kevin Ruddock
Kevin Ruddock
18,323 Points
Kevin Ruddock
Kevin Ruddock
18,323 Points

Much appreciated Steven!

Henry Ojukwu
Henry Ojukwu
2,475 Points
Henry Ojukwu
Henry Ojukwu
2,475 Points

Hope this helps To Stub out a class for the purpose of running a test, you are basically required to write the constructor(s) and method(s) of the class, however, the method(s) should not be implemented as this is merely the red stage of the red-green-refactor programming concept. The ultimate goal of stubbing out a class is to ensure that all of it's methods fail at runtime before the actual implementation of those methods.

For the Calculator class, try the below sample code and see how it goes

Hope this helps!

using System;

public class Calculator { public double Result; public Calculator (double result) { Result = result; } public void Initialize() { }

public void Add(double val)
{ 
}

}