Introduction
Software development is a complex process that involves many steps, such as planning, designing, coding, testing, and deploying. To ensure the quality and functionality of the software, developers use different methods and tools to guide their work. Two of the most popular methods are Behaviour Driven Development (BDD) and Test Driven Development (TDD). In this article, we will compare and contrast these two methods, and explain how they can help developers create better software.
What is Behaviour Driven Development?
Behaviour Driven Development is a method that focuses on the behaviour of the software, rather than the implementation details. It uses a simple and natural language, called Gherkin, to describe the features and scenarios of the software. For example, a feature of a calculator app could be described as:
Feature: Addition
As a user
I want to add two numbers
So that I am able to view the outcome.
Scenario: Add two positive numbers
Given I've input 10 into the calculator.
And I've input 20 into the calculator
When I press add
Then the result should be 30
The Gherkin language helps developers, testers, and stakeholders to communicate and collaborate more effectively, as they can easily understand the requirements and expectations of the software. It also helps to create automated tests, as each step in the scenario can be mapped to a code snippet that executes the action or verifies the outcome.
What is Test Driven Development?
Test Driven Development is a method that follows a cycle of three steps: red, green, and refactor. It means that developers write tests before writing code, and use the tests to guide their coding. For example, a test for the addition feature of the calculator app could be written as:
function test_add_two_positive_numbers() {
let calculator = new Calculator();
calculator.enter(10);
calculator.enter(20);
calculator.add();
assert(calculator.result == 30);
}
The test is initially red, meaning that it fails, as there is no code to implement the feature. Then, the developer writes the minimum amount of code to make the test green, meaning that it passes. Finally, the developer refactors the code to improve its quality and readability, without changing its behaviour.
The TDD method helps developers to write code that is clean, simple, and bug-free, as they only write code that is necessary to pass the tests, and they constantly check and improve their code. It also helps to create a comprehensive and reliable test suite, as the tests cover all the features and scenarios of the software.
How are they different?
BDD and TDD are both methods that use tests to drive the development of software, but they have some key differences. The main difference is the perspective that they adopt: BDD focuses on the user's perspective, while TDD focuses on the developer's perspective. This means that BDD starts from the outside of the software, describing the behaviour and features that the user expects, while TDD starts from the inside of the software, writing the code and tests that implement the functionality.
Another difference is the language that they use: BDD uses a natural language, such as Gherkin, that is easy to read and write by anyone, while TDD uses a programming language, such as Javascript, that is more technical and requires coding skills. This means that BDD is more accessible and collaborative, as it can involve non-technical people, such as customers and business analysts, while TDD is more precise and efficient, as it can directly translate the tests into code.
A third difference is the level of testing that they perform: BDD usually performs higher-level testing, such as acceptance and integration testing, that verify the behaviour and interaction of the software as a whole, while TDD usually performs lower-level testing, such as unit and component testing, that verify the functionality and structure of the software's parts.
How are they similar?
BDD and TDD are also methods that have some similarities. The main similarity is the goal that they share: to create software that meets the needs and expectations of the users and stakeholders, and that is high-quality and reliable. Both methods use tests to validate and verify the software, and to guide and improve the development process.
Another similarity is the benefits that they provide: both methods help to reduce the cost and time of development, as they prevent and detect errors early, and avoid rework and waste. They also help to increase the satisfaction and trust of the users and stakeholders, as they deliver software that works as intended, and that is easy to use and maintain.
A third similarity is the challenges that they face: both methods require a change in the mindset and culture of the developers and the organization, as they need to adopt a more test-oriented and collaborative approach. They also require a balance between the quantity and quality of the tests, as they need to write enough tests to cover all the aspects of the software, but not too many tests to make the testing process slow and complex.
Conclusion
Behaviour Driven Development and Test Driven Development are two popular methods that use tests to drive the development of software. They have some differences, such as the perspective, language, and level of testing that they use, but they also have some similarities, such as the goal, benefits, and challenges that they share. Both methods can help developers create better software, but they need to be used appropriately and effectively, depending on the context and the needs of the project.
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