As the name suggests, TDD is a test-driven technique for delivering high-quality software rapidly and sustainably. It is an iterative approach based on the idea that a failing test should be written before any code for a feature or function is written. Test-Driven Development (TDD) is an approach to software development that relies on very short development cycles.
Understanding Test-Driven Development
Test-Driven Development has had a significant influence on software design, with a particular focus on non-functional requirements such as usability, security, and maintainability.
A typical Test-Driven Development cycle
TDD invariably follows the “Red-Green-Refactor” cycle, described as follows:
- Start by adding a test unit to the test suite. This test unit should describe an aspect of the program.
- (Red) Run all tests, which should fail because the program lacks that feature.
- (Green) Write just enough code in the simplest way possible to enable the test to pass. This step is sometimes called “make it pass”.
- Run all tests once again.
- (Refactor) Enhance the original code while keeping tests green. Ensure that a focus on simplicity is maintained.
- Repeat and accumulate unit tests over time.
Strengths and weaknesses of TDD
- Increased code quality resulting from the reduction in defects and errors. TDD forces developers to consider the purpose and specification of code. It also helps developers simplify code writing and avoid complex code that can harbor bugs. Lastly, TDD refactoring ensures that code changes or new code do not impact the integrity of the existing code.
- Reduction in batch size. In other agile methodologies, developers work on a feature until completion with little input from others. TDD encourages the developer to reduce the batch size to improve project visibility, flexibility, and stakeholder collaboration. Ultimately, this also makes TDD a customer-centric agile process.
- Encourages high developer morale. On occasion, developers become demoralized in the face of large and complex projects. TDD distills large projects into many smaller pieces that deliver quick and relatively easy wins for the developer. In addition to improving morale and confidence, the developer knows what has been completed and what work remains to be completed.
- May take more time to implement initially. Programmers who have become accustomed to writing code that can be run immediately may find TDD slow and difficult to implement. The same can be said for programmers who have never written tests in the first place. However, any perceived slowness is an illusion at best. Although TDD may take some getting used to, it does deliver significant benefits to efficiency as development progresses.
- Poorly maintained or abandoned test suites. A lack of test suite maintenance can lead to a TDD cycle with a prohibitively long running time. Test suites may be also be abandoned or seldom run because of poor maintenance or changes to team composition.
- Test-Driven Development is an agile software development approach that favors the rapid delivery of very short development cycles.
- Fundamental to Test-Driven Development is the “Red-Green-Refactor” test cycle. TDD argues that fail tests should be conducted before any feature or function code is written.
- Test-Driven Development increases code quality and developer morale while reducing batch sizes. However, some project teams may experience a steep initial learning curve – particularly if they are unaccustomed to the methodology.
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