Why Unit Test Coverage is so Important (and why it might be over-emphasized too fliply in some circumstances)

We at mcode believe a minimum 60% unit test coverage is about right. We'll get you there. Call us now.

Arguments for unit test coverage in code bases:

1. Increased code quality: Unit tests provide a safety net against bugs and errors by catching them early in the development cycle, which leads to improved code quality. Unit testing helps identify and fix issues promptly before they propagate throughout the system.

2. Better maintainability: Tests act as documentation for the code, helping developers understand how the code is intended to be used and indicating what breaks when a change is made. They promote better understanding of the codebase and make it easier to maintain or refactor the code.

3. Faster regression testing: Re-running automated unit tests verify that changes or new additions in the code do not break existing functionality. This speeds up the overall testing process and enables robust regression testing.

4. Supporting collaboration and team confidence: Unit testing provides a form of code review, making it easier for different team members to assess the functionality without relying solely on human interpretation. The presence of comprehensive unit tests provides confidence to both the developers and the project stakeholders.

Arguments against unit test coverage in code bases:

1. Time-consuming and high cost: Writing and maintaining unit tests can add significant overhead to the development process, requiring additional resources and effort. This time and cost may not always be justifiable for small, simple or short-lived projects.

2. False sense of security: While high code coverage tends to give a sense of confidence, it does not guarantee bug-free or fault-tolerant code. Unit tests can only catch errors on a specific level of granularity, often missing the bigger picture and integration issues between components.

3. Limited applicability and low-business gain: In some cases, the benefits derived from comprehensive unit testing may not offset the investment required. For certain applications or use cases, the risks may be well-understood and controllable, making full unit test coverage unnecessary at a proportionate scale.

4. Solution overhead: The efforts to maintain and update unit tests may impact the solution’s robustness, as code alterations lead to cascading test updates, increasing debugging efforts as well. There could be critical stages where formal testing and exploration uptake wants the immediate refinement over test suites procedures.

These arguments should consider the trade-off aspects: project requirements, project scale, delivery schedule, available resources, development priorities, and many other contextual factors can influence whether extensive unit test coverage is beneficial or not for a given codebase.