Introduction

This lesson presents the solution to the challenge to implement a simple probability calculator, followed by the test methods to verify its correctness.

Solution to challenge

The project solution is shown in the widget below. Run the widget to see that all tests pass:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Project
{
    public class Calculator
    {
        public int Factorial(int n) 
        {
            if (n < 0)
            {
                throw new ArgumentException();
            }
            //The if statement below caters for the special case where the
            //input is the value of zero
            if (n == 0)
            {
                return 1;
            }
            for (int i = n - 1; i > 0; i--)
            {
                n *= i;
            }
            return n;
        }

        public int Npr(int n, int r)
        {
            if (n < 0 || r < 0 || r > n)
            {
                throw new ArgumentException();
            }
            return Factorial(n)/Factorial(n - r);
        }

        public int Ncr(int n, int r)
        {
            if (n < 0 || r < 0 || r > n)
            {
                throw new ArgumentException();
            }
            return Factorial(n) / (Factorial(r) * Factorial(n - r));
        }
    }
}

The solution to the challenge

Fundamentals of Unit Testing

Testing Conditions With Classic And Fluent Assertions

Making Unit Testing More Effective

Unit Testing Code with External Dependencies

Conclusion

Appendix - Unit Test Project Organization and Console Setup

Solution: Unit Test Using Test After Development

Introduction

Solution to challenge

Code walkthrough