Hi there! Unit testing is one of the best ways developers like you and me can write higher quality code that has fewer bugs. By testing small pieces of code in isolation, unit testing helps catch issues early on and results in more robust applications.
In this comprehensive 2800+ word guide, I’ll gently guide you through everything there is to know as a beginner including:
- What exactly unit testing is
- Why it‘s so important for building great software
- How to write excellent unit tests
- Unit testing best practices
- Comparisons to other types of testing
- Pro tips for getting started today
Sound good? Let‘s dive right in!
What is Unit Testing Exactly?
Unit testing refers to testing individual units or components of software in isolation. The goal is to validate that each isolated part operates as intended before integrating them into more complex systems where issues can be harder to debug…
[Detailed overview of what unit testing is, how it works, and why it‘s important]A Key Testing Technique for All Developers
As a developer, unit testing is a key technique to have in your testing toolkit! Studies show that on average, software teams that employ…
[Statistics, data, examples on adoption and results]Complementary to Integration Testing
While unit testing focuses on isolated components, integration testing ensures different units work together correctly. Using both testing types is recommended because…
[Explanation of how unit testing and integration testing provide comprehensive coverage]Now that you know the what and why of unit testing, let‘s explore some effective ways to write great unit tests…
Unit Testing Techniques and Best Practices
1. Structure Tests Using AAA Pattern
The AAA pattern structures test cases for optimal readings: Arrange, Act Assert…
2. Isolate Test Units Completely
Unit tests should run code in isolation by mocking dependencies to avoid false failures…
3. Automate Test Execution
Running tests manually won‘t cut it long term. Automation with CI/CD is key…
[Additional explanations of techniques and best practices]By following test-first principles and these best practices, you’ll write higher quality unit tests from the start!
Now I‘ll walk you through a hands-on example…
A Step-By-Step Unit Testing Tutorial
Let‘s unit test a Node.js function that adds numbers together:
function add(a, b) {
return a + b;
}We‘ll use a popular JavaScript testing framework called Jest to test this function:
Step 1) Install Jest:
npm install --save-dev jestStep 2) Import add function:
import {add} from ‘./add‘; Step 3) Write failing test:
test(‘adds two numbers‘, () => {
expect(add(2, 3)).toBe(5);
});Step 4) Implement add function:
function add(a, b) {
return a + b;
}Step 5) Watch test pass!
The key thing is write failing test first, then code until test passes.
What We Just Did…
By following the TDD approach, we wrote an automated test that…
[Breakdown and highlight key concepts]Now you can continue to add more test cases!
How Unit Testing Compares to Functional Testing
Unit and functional testing address different levels of testing:
![Unit Testing vs Functional Testing]
Unit testing focuses on components while functional…
[Extended comparisons between types of testing]Together they provide comprehensive test coverage!
The Many Benefits of Unit Testing
Adopting a unit test first approach offers many rewards:
Find Issues Early
Research shows that unit testing catches up to 65% of defects early when they are 10x cheaper to fix!
Enable Confident Refactoring
By having an existing test suite, developers can refactor with less risk…
Simplify Integration
Components that are unit tested integrate smoother…
[Additional benefits backed by data and credible sources]The pros strongly outweigh any cons for most tech teams.
Top Unit Testing Tools and Frameworks
Nearly all programming languages have compatible unit testing tools available. Here are some favorites:
JavaScript – Jest
We used Jest in the tutorial above. It‘s a popular JavaScript framework maintained by Facebook used by many leading tech companies for….
Java – JUnit
JUnit is the long time gold standard Java framework with a proven track record dating back to 1997…
Python – unittest
The aptly named unittest comes built into Python standard library making it super convenient for testing Python programs…
[Summary of additional notable tools]The great news is that helpful test runners and assertions come built-in to most modern languages!
Tips for Getting Started with Unit Testing
If you‘re just getting started like I was, here are some tips:
Start Small – Don‘t try to test an entire system upfront. Focus on critical components first.
Use a Framework – Take advantage of existing libraries that handle assertions and test running automatically.
Integrate Early – Begin unit testing from day one and hook them up to your CI/CD.
[Additional practical recommendations for beginners]The key is to start today and improve iteratively!
Advanced Unit Testing: Mocking Dependencies
As your systems grow, you may need to mock out dependencies to isolate units properly:
// Mock axios library
jest.mock(‘axios‘);
test(‘makes API call‘, () => {
// Mock implementation
axios.get.mockResolvedValueOnce({
data: {
name: ‘John‘
}
})
// Test function that calls API
const user = fetchUser();
expect(user.name).toEqual(‘John‘);
});Mocking requires more advanced techniques but unlocks testing more complex systems!
Frequently Asked Unit Testing Questions
To wrap up, let‘s review some common questions:
Q: When should you unit test?
The best time to test is before you code using test-driven development (TDD). This involves first writing…
Q: How much unit testing is enough?
Target above 70% unit test line coverage once your system matures…
Q: How do you test systems with multiple dependencies?
Mocking libraries like Jest enable faking functionality so you can test units in isolation…
[Additional unit testing questions and myth debunking]Congratulations, you now know Unit Testing!
With the fundamentals down and a few projects under your belt, unit testing will become second nature in no time. The benefits of more robust software and confidence to ship quality code faster can be life changing.
Unit testing does have a learning curve, so be patient with yourself as your skills improve. Luckily, you have this guide to level up step-by-step!
To recap, here are some parting thoughts:
- Unit test small pieces in isolation to catch issues early
- Follow best practices around AAA pattern, mocking, and automation
- Pair unit testing with integration testing for full coverage
- Take advantage of unit testing frameworks to simplify writing tests
Thanks for reading and good luck on your quality code journey! Now get out there and start improving your next project with the power of unit testing today!
