Gain insights into unit testing principles, and delve into configuring and using NUnit. Discover how to write effective tests, maximize coverage, and elevate your testing projects.

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Industry, employers, startups, and amateur developers are increasingly looking towards unit testing their software. Unit testing is one of the most reliable ways to find and keep software bugs at bay, thus reducing costs and development pains. Developers working with the .NET framework are overwhelmingly turning to NUnit to meet their unit testing needs.

In this course, you’ll learn the principles of unit testing, and in the process, learn to configure and use the NUnit testing framework. Given that the course places an emphasis on principles, these skills are transferable to other unit testing frameworks. Alongside these, you’ll also get hands-on experience with projects and exercises that provide ample opportunities to learn how to design effective tests in the NUnit framework.

At the end of the course, you’ll be able to quickly write unit tests that maximize logical coverage, test complex applications, and better organize your testing projects—setting you up as a natural leader in your organization.

Mastering Unit Testing Principles with NUnit

# 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:



import React from 'react';
import { shallow, configure } from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';

configure({ adapter: new Adapter() });

import HelloWorld from './app';

var TestResult = function() {
    this.succeeded = false;
    this.reason = "";
    this.input = "";
    this.expected_output = "";
    this.actual_output = "";
}

export const executeTests = function() {

  var results = [];

  result = new TestResult();
  result.input = 'HelloWorld Component';
  result.expected_output = "span containing text 'Hello World'"

  let wrapper = shallow(<HelloWorld />);

  // Call your Challenge function here.

  let type = wrapper.type();
  let testSuccessful = true;
  let failureReason;

  if (type !== 'span') {
    testSuccessful = false;
    failureReason = "You need to render exactly one span HTML element";
  } else if (wrapper.props().children != "Hello World") {
     testSuccessful = false;
     failureReason = "You have rendered wrong message in your span element";
  }

  result.actual_output = wrapper.html();

  if (testSuccessful) {
    result.succeeded = true;
    result.reason = "Succeeded"
  } else {
    result.succeeded = false;
    result.reason = failureReason;
  }

  results.push(result);

  return results;
}


React

Dart

GoJS React

Typescript React

Vue.js

# Code walkthrough

The application code contains a single class called `Calculator` with three public methods:
- `Factorial` (**line** **11**)
- `Npr` (**line** **30**)
- `Ncr` (**line** **39**)

The `Factorial` method is not only a public method but is also used to calculate the return values of the `Npr` and `Ncr` methods.

To cater for values that are out of range, all three public methods throw exceptions if the input contains negative numbers. Furthermore, both `Npr` and `Ncr` throw exceptions if the first parameter is less than the second parameter (**lines 13–16**, **32–35**, and 41–44).

All unit tests are contained in the file `CalculatorTest.cs`. There are six test methods:
- Testing `Factorial` (line **22**)
- Testing `Factorial` exceptions (line **28**)
- Testing `Npr` (**line** **39**)
- Testing `Npr` exceptions (**line** **45**)
- Testing `Ncr` (**line** **56**)
- Testing `Ncr` exceptions (**line** **62**)

Since the `Calculator` class needs to be instantiated for each test, its instantiation is done in the setup method (**line** **15**).

> **Note:** The test methods have test cases to test edge cases where the arguments are equal to $11$, $10$, or $-1-1$.

# Conclusion

This lesson presents the solution to the challenge posed in the previous lesson. Once you have compared your attempt to the solution above, ask yourself the following questions:
- Are there any areas of code that you missed?
- Between your code and the solution, which areas differed and why?
- If you could not complete some code sections, look at the solution and then attempt those sections again.
- Could any of the code in the solution above be improved?

Learn the solution to the test after development challenge and learn from your mistakes.

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