Testing: The Big Picture
the Goal of Testing
Most developers agree that as a project grows, having a test suite is essential. But why is that? At first glance, you might think a test suite is valuable because it catches errors as you add or edit code. While that's true, it doesn't capture the whole picture. The real value of tests is that they help your codebase scale efficiently. Understanding this is crucial because it helps us determine if a test is good or bad and whether the test suite is doing its job.
Improving Scalability
At the start of a software project, developers usually have the entire code base fresh in their minds, and the product’s value proposition might still be unclear. During this phase, it often makes more sense to focus on building new features and setting up the infrastructure rather than spending time on writing tests. However, as the code base grows, so does its complexity. It becomes harder for a single developer to predict the side effects of changes or to understand the original intention behind another developer’s contributions. While clean, modular code can help, no project is perfect.
Incorporating tests as your project matures is crucial. Tests ensure that new code doesn’t disrupt existing functionality and that changes don’t break anything, leading to more stable and steady development over time. Skipping tests might speed up development initially, but as the project grows, managing its complexity without tests can slow down progress significantly.
What makes a good test
A test’s value can thus be measured by the degree it benefits the scaling of the project, and the cost to deliver on that value.
Test Cost
Refactoring required when code under test is changed
Time spent running the test
Dealing with false alarms raised by test
Time spent reading the test to understand its purpose
