The Importance of Unit Testing
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Despite how critical testing is to modern software engineering, I graduated with a Computer Science degree without ever learning a single thing about it. My first two jobs out of college didn’t change that; we simply didn’t write tests. It wasn’t until my third company that I actually learned the importance and power of testing, specifically, the unit test.
The turning point happened when I picked up a ticket to fix a bug. After a ten-minute chat with my manager, everything clicked. He explained that instead of just trying to fix the code, I should first write a test that proves the bug exists. This involved writing a test case for what should happen, and then watching that test fail. Only then would I update the implementation logic to fix the bug and rerun the test to see it pass.
This process is transformative. It doesn’t just fix the immediate problem; it creates a permanent guardrail. You are essentially protecting that logic from any future regressions. Once that test is in the suite, nothing can be committed to the codebase, alone pushed to production, if it breaks that specific logic.
This realization led me down a rabbit hole of testing methodology. I started learning about the testing pyramid, integration tests, end-to-end tests, smoke tests, and even mutation tests. But at the foundation of it all are unit tests. They are the smallest, simplest form of testing and should comprise the vast majority of your suite.
To make this work in a real-world workflow, speed is everything. Your unit test suite must be fast. The faster your tests run, the more often you will be willing to run them. When your suite is near-instant, it changes the way you work. It gives you the freedom to refactor with total confidence. You can rip apart and rebuild the logic however you see fit; as long as the tests still pass, you know you haven’t modified the existing behavior or broken the “contract” of the code.
Testing isn’t as scary as it seems when you’re looking at it from the outside. In fact, it’s one of the most powerful tools for increasing your productivity. It allows you to develop code quickly and, more importantly, safely. If you haven’t started yet, stop guessing if your code works and start proving it.
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Great article Kevin. Thanks for sharing