What is Test-driven Development and Why Should Business Owners Care
Test-driven Development (TDD) is a software development approach in which test cases are created first based on software requirements to specify and validate how developers should write code.
TDD guides developers to create clean, simple, and efficient code that meets software requirements to avoid or minimize excessively long code.
TDD provides several benefits to your software development process. These are as follows:
It makes debugging easier.
It makes programming more fun.
It helps developers write extensible and maintainable code.
It helps reduce maintenance costs.
It minimizes technical problems.
It makes teams' performance more efficient.
If you want to know more about TDD, this post talks about:
The Different Phases of Test-Driven Development
Test-Driven Development (TDD) aims to ensure that software code implementations are tested thoroughly at their early stage of development.
There are three phases of TDD, these are as follows:
- Red. In this phase, developers write a short test for the specific behavior of a function that should fail.
- Green. In this phase, developers write the easiest and simplest code implementation required that passes the test.
Refactor. In this phase, developers review and check the code implementation for some redundancy or possible optimizations to improve the overall performance of the code.
The following are the questions that need to consider before you refactor your code:
Can your test suite be written to be more expressive?
Does your test suite provide reliable feedback?
Are the performed tests isolated?
Can you make the code implementation more efficient and descriptive?
Can your test suite or code implementation duplication be reduced?
The red, green, and refactor phases help developers to create an efficient solution for the specified requirements or behavior of a system.
The Different Levels of Test-Driven Development
The test-driven development approach has two different levels, these are as follows:
- Acceptance TDD (ATDD). In ATDD, a single acceptance test is created to satisfy the specified requirements or behavior of the system. It is also known as Behavioral Driven Development (BDD) as it focuses on testing the overall system behavior.
- Developer TDD (DTDD). In DTDD, a developer writes just enough code to pass a single test.
The main purpose of ATDD and DTDD is to provide detailed and executable requirements needed by the system to increase efficiency.
The Advantages of Test-Driven Development
TDD provides several advantages to your software development process. These are as follows:
Better and improved code quality. With TDD, developers become more responsible for creating better, cleaner, maintainable, and more extensible code with well-designed system architecture. TDD enables developers to focus more on defining better system requirements in order to improve implementation.
TDD promotes good coding principles such as DRY, KISS, YAGNI, and SOLID.
The DRY (Don’t Repeat Yourself) principle does not allow any duplicate code in a different part of a system.
The KISS (Keep it Simple, Stupid) principle promotes simplicity as the key design principle for every system.
The YAGNI (You Ain’t Gonna Need It) principle encourages developers to implement only assigned tasks and avoid adding unnecessary functionality.
SOLID is composed of five coding principles that aim to make applications easier to maintain and test. These are as follows:
Single responsibility. This principle states that each class, function, or module should have one single purpose and responsibility.
Open-closed. This principle tells developers that new software features should be added easily without modifying the existing code.
Liskov substitution. This principle states that superclass objects should be replaceable with their subclasses objects without breaking the application.
Interface segregation. This principle tells to break application interfaces into smaller and more specific ones to reduce large interface side effects.
Dependency inversion. This principle states that high-level and low-level modules should depend on abstractions.
- Early bug detection and prevention. In TDD, developers create the entire test suites for the overall system functionality at the beginning and run tests regularly to prevent bugs instead of fixing them after the code is written. TDD promotes and ensures higher test coverage compared to other conventional development models.
- Decreases the project development costs. The TDD approach promotes higher test coverage that helps avoid or lessen issues when adding new features to the system. Fewer issues require fewer developer hours and reduce the time required for project development. As a result, it decreases the overall costs of the project development in the long run.
- Improves developers' productivity. Despite spending more time in writing test cases during the early development phase, TDD increases developers' speed and productivity for they do not spend more time debugging and developing new features. Developers write simple, clean, flexible, and easy to maintain code.
- Detailed Documentation. With TDD, the test created for the specified system requirements generates a strict and detailed specification of how its functionality works. These tests can serve as detailed project documentation for developers to check on how a certain function behaves in different scenarios.
The Limitations of Test-Driven Development
The following are some of the limitations of TDD:
- Developers may experience difficulties in adopting the test-driven development approach effectively.
- Unit tests in a TDD environment can have possible shared blind spots with the code since they are created by the same developer.
- TDD is not capable to perform full functional testing to identify success or failure in areas like user interfaces, programs intended for databases, and other code implementations that depend on specific network configurations.
- Poor architecture, design, and testing strategy can lead to multiple test failures and undetected holes in the test coverage.
- Poor maintenance of test suites due to an excessive number of tests and/or team turnover.
The Popular Test-Driven Development Tools
There are several unit testing frameworks or tools that support test-driven development approach. These are as follows:
- PHPUnit is a unit testing framework for PHP projects.
- csUnit and NUnit are the open-source unit testing framework for .Net projects.
- PyUnit and DocTest are the popular unit testing framework for Python.
- Rspec is a unit testing framework for Ruby projects.
- Junit and TestNG are unit testing frameworks or tools for Java.
- Jest is a testing framework for JavaScript that focuses on simplicity.
Adapting test-driven development approach in your software development project can be very helpful in producing a highly functional, extensible, fault-tolerant, and maintainable system.
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