Once we're happy, we can move to the next feature, right? We can test the first feature manually and see if it's still working. The result is that it's so incredibly expensive to manually test all features whenever a new release is made, that projects without TDD are very prone to regressions.
In software development terms, a regression happens when a feature that was working in a previous release appears to be broken on a later release. The conclusion is that projects where TDD is applied usually have fewer bugs than projects with no automated tests. But automated tests are not free. However, as complexity of the software grows, it becomes increasingly difficult to manually test every single feature. After the implementation of a few features, investing time in writing automated tests already pays off.
In the software development community, it is now widely accepted that projects with automated tests are less buggy than projects without automated tests.
It is also widely accepted that the overhead of writing a test pays off by preventing bugs from hitting the production environment. Fewer bugs means a better product. And that usually translates in happier users. Not to mention happier developers, who can spend their time making a better product, instead of constantly fixing bugs. But how much testing is enough?
Do we need to write automated tests for every single feature? In TDD there is no formal test plan, making it an informal process. Therefore, the percentage of code that needs to be tested is a huge debate. As new features were being released with lower coverage, we started to get more regressions. Had we not had a drop in coverage, we would be delayed only by half-a-sprint, instead of a full sprint.
This significantly optimizes the refactoring task and the overall process time. If at any point in this process, new bugs are detected, they get included in the unit tests and are followed by code development to fix them. TDD helps developers understand and learn the principles of modular design when writing tests for very small features. TDD makes refactoring and maintenance much easier.
As all functionality is covered by tests, any change in code that might introduce an error is easily detectable, since unit tests begin to fail. This way, developers can be sure that when they revisit prior version code, changes can be made with confidence.
When the code is modular and the changes impact smaller pieces of functionalities, the risk associated with breaking other parts of the code decreases. When maintenance is efficient and bug detection is faster, project costs decrease. A best practice is to give intuitive names to the unit tests. TDD also ensures that only necessary code is produced, and no production code exists without its respective tests.
The code that is written to successfully pass tests is the minimum possible, and over-coding is avoided. TDD compels the team to define the functionalities as comprehensively and clearly as possible right from initial stages, as these functionalities need to be fully understood in order to start writing tests. Therefore, TDD has collaboration at its core. Anyone in the team can work on another team members' code, since tests are used to determine any issues.
Tests also serve as documentation, as outlined earlier. Through its test-first approach, it gives developers the opportunity to consider more carefully the usability challenges users are likely to face. Tests ensure that the code stays focused and clear during each stage of development. Automated tests, for example, can highlight mistakes and their impact on the system, which in turn enables developers to detect bugs and other problems that arise as a result of the changes they have most recently made to the code.
It becomes easier for them to create software that is solid and works as intended. The codebase gets cleaned up constantly through refactoring, making room for new code to be added. This process can tighten up the code and place it where it belongs in the codebase. The result is a tidy codebase free from unnecessary duplication, which makes the software easier to tweak and maintain. TDD requires developers to write code in response to test requirements.
This approach promotes the simplification of code. It can prevent excess code and helps keep the codebase streamlined and easy to use. There are no doors left open for superfluous code to creep into the software. Tests create quality metrics for the code.
The team of developers can use TDD to effectively determine how good the code is. In this way, they can develop more consistent code and fix any cracks they spot in it. TDD encourages developers to build software using small units of testable code. Fast iterations mean that developers can receive feedback from clients more quickly than with traditional approaches to software development. They can then use this feedback to craft a more polished piece of software.
Clients also benefit. They can choose to be more involved in the development project and review iterations more frequently. Other developers can use completed tests as usage examples for the code, allowing them to become familiar with it faster.
This can make the project more friendly for developers other than those who build the code from the ground up. For long-term projects which may pass through multiple hands, this documentation can be valuable.
The test-and-code approach increases the productivity of the development team by focusing their energy on passing tests, that is, accomplishing goals. TDD enables you to develop a functional piece of code for end-users in a shorter time span than many other programming practices.
0コメント