# TDD: Writing Testable Code

DevFeed: [TDD: Writing Testable Code](<https://devfeed.tech/articles/tdd-writing-testable-code-20716.md>)

Original publisher: [Read original article](<https://medium.com/javascript-scene/tdd-writing-testable-code-30ac7a3bf49c?source=rss----c0aeac5284ad---4>)

Author: Eric Elliott

Published: 2024-01-21T23:50:43Z

Content type: tutorial

Language: en

Sources: [Eric Elliot](<https://devfeed.tech/sources/eric-elliot.md>)

Topics: [Test-driven development](<https://devfeed.tech/topics/tdd.md>), [Software Engineering](<https://devfeed.tech/topics/software-engineering.md>), [coding](<https://devfeed.tech/topics/coding.md>), [CI/CD](<https://devfeed.tech/topics/cicd.md>)

Tags: [advice](<https://devfeed.tech/tags/advice.md>), [complexity](<https://devfeed.tech/tags/complexity.md>), [defects](<https://devfeed.tech/tags/defects.md>), [javascript](<https://devfeed.tech/tags/javascript.md>), [modularity](<https://devfeed.tech/tags/modularity.md>), [react](<https://devfeed.tech/tags/react.md>), [software-engineering](<https://devfeed.tech/tags/software-engineering.md>), [tdd](<https://devfeed.tech/tags/tdd.md>), [technology](<https://devfeed.tech/tags/technology.md>), [typescript](<https://devfeed.tech/tags/typescript.md>)

## AI overview

This tutorial explains how to write more testable code through modularity, clarity, separation of concerns, and independence from external systems. It also describes tight coupling as a barrier to testability and maintainability, noting that dependencies can cause changes to cascade into bugs elsewhere.

## Source excerpt

Writing testable code is a vital skill in software engineering. Let's explore practical advice, strategies, and tactics for writing more testable code, unlocking the benefits of modularity, reusability, and high quality software in your projects. Embracing testability in your coding practice isn't just about catching bugs; it's about fostering a culture of quality and efficiency in your projects. A good quality process is an essential prerequisite to continuous delivery, which is the ability to ship code to production at any time, allowing you to iterate quickly and respond to user needs and changing expectations. We'll start by exploring the importance of separation of concerns -- a principle that's crucial in achieving testable code. This approach isn't just a technical necessity; it's a mindset that simplifies complexity and enhances the overall quality of your work. Whether you're a seasoned developer or just starting out, this article aims to provide practical advice and strategies that can be immediately applied to your projects. Overview of Testability in Code Testability in code refers to how easily a software system can be tested. Highly testable code allows for more efficient and effective identification of defects, ensuring higher quality and reliability. Key characteristics of testable code include modularity, where the code is organized into discrete units; clarity, meaning the code is understandable and its purpose is clear; and independence, where units of code can be tested in isolation without reliance on external systems or states. Understanding the Problem: Tight Coupling in Code Tight coupling is often a subtle yet significant barrier to achieving highly testable and maintainable code. Coupling is the degree to which a change in one part of the code may impact or break the functionality in another part of the code. Tight coupling occurs when two or more parts of the code are highly dependent on each other, making it difficult to change one part wi