Challenge: Unit Test Using Test After Development

Introduction

In this project, you’ll write a unit test that tests the behavior of a class using the test after development approach. An assessment rubric is provided to give you an indication of whether the principles taught in this section have been applied.

Self-assessment rubric

I have…	Emergent	Satisfactory	Excellent
Used parameterized tests	Did not use parameterized tests	Partially used parameterized tests	Used parameterized tests for test methods, wherever appropriate
Used a setup method	No setup method used	N/A	Setup method used
Pitched the tests at the right level	Inconsistent test approach—a combination of high-level and detailed approaches used	N/A	Consistent test approach—either a high-level or detailed approach adopted

Quick dive into probability before unit testing

The challenge requires us to write code that calculates factorials, permutations, and combinations. Below is a brief description of each.

Factorial

The following is an outline of the factorial operation.

Calculation and example

$n!$ is the product of all positive integers less than or equal to $n$, $n! = n{\times}(n-1){\times}(n-2){\times}...{\times}3{\times}2{\times}1$

For example: $5! = 5{\times}4{\times}3{\times}2{\times}1 = 120$

Meaning of factorial

This operation is used in probability calculations where we want to find out the number of different ways to arrange ...