General
Test-Driven Development (TDD), Behavior-Driven Development (BDD), and Acceptance Test-Driven Development (ATDD) are three distinct yet interconnected approaches that help developers create robust and reliable software.
TDD is primarily focused on unit testing and code functionality, BDD centers on system behavior and stakeholder collaboration, and ATDD aligns development with user requirements through acceptance criteria.
Understanding these distinctions can help teams leverage the strengths of each methodology, fostering a more efficient and effective development process.
Test Driven Development (TDD)
Test-Driven Development is a testing methodology or a programming practice implemented from a developer’s perspective. In this technique, a QA engineer starts designing and writing test cases for every small functionality of an application. This technique attempts to answer a simple question – Is the code valid?
The main intention of this technique is to modify or write a fresh code only when the test fails. Hence it results in lesser duplication of test scripts. This technique is prevalent mainly in agile development ecosystems. In a TDD approach, automated test scripts are written before functional pieces of code. The TDD methodology involves the following steps:
A developer writes an automated test case based on the requirements specified in the documents. These tests are executed, and in some cases, they fail as they are developed before the development of an actual feature. The development team then re-factors the code for the test to pass successfully. TDD can be done by a single developer while writing both tests and application code side by side to complete a feature. Refactoring refers to modifying the code without changing its main functionality or behavior.
Benefits of TDD
- Reduces the amount of time required for rework
- Explores bugs or errors very quickly
- Faster feedback
- Encourages the development of cleaner and better designs
- Enhances the productivity of the programmer
- Allows any team member to start working on the code without a specific team member. This encourages knowledge-sharing and collaboration.
- It gives the programmer confidence to change an application’s large architecture quickly.
- Results in the creation of extensive code that is flexible and easy to maintain
How to perform TDD
Incorporating Test-Driven Development (TDD) into your software development process can significantly enhance code quality and reduce the likelihood of defects. By following the iterative cycle of writing a test, developing the code, and refactoring, teams can ensure that their software meets its requirements and is adaptable to future changes.
The structured approach outlined above helps to clarify the roles and responsibilities of various stakeholders, facilitating collaboration and efficiency throughout the development lifecycle.
| Step | Description | Stakeholders Involved |
|---|---|---|
| 1. Write a Test | Create a test for a small piece of functionality. This test should initially fail as the code does not yet exist. | Developers |
| 2. Run the Test | Execute the test suite to ensure the new test fails, confirming that the functionality is not implemented yet. | Developers |
| 3. Implement Code | Write the minimal amount of code required to pass the test. Focus on just enough implementation to satisfy the test condition. | Developers |
| 4. Run Tests Again | Run all tests again, including the new test, to check if the new code passes and does not break existing functionality. | Developers |
| 5. Refactor Code | Optimize the newly implemented code while keeping the functionality intact. This may involve cleaning up code, improving structure, or enhancing performance. | Developers |
| 6. Repeat | Continue this cycle for each new feature or piece of functionality, gradually building the application with a solid test suite. | Developers, Project Managers |
TDD Example
Step 1: Write a Test
Define a test case for the functionality you want to implement such as, the addition of two numbers – “Adding 1 and 2, the result should be 3.”
Step 2: Run the Test
Execute the test. Since the addition function hasn’t been implemented yet, this test will fail, confirming that the functionality is currently absent.
Step 3: Implement Code
After the test fails, the next step is to write the minimum code necessary to make the test pass. It involves creating a function that performs the addition of the two numbers specified in the test.
Step 4: Run Tests Again
Run the test suite again, including the newly added test for the addition function. At this point, the addition test should pass, indicating that the implementation works as intended.
Step 5: Refactor Code
Once the test passes, the next step is to review the code for any potential improvements. This could involve simplifying logic, improving naming conventions, or optimizing performance while ensuring that the functionality remains intact.
Step 6: Repeat
Finally, the process is repeated for additional functionalities. For each new feature, you would write a test, run it to see it fail, implement the code, run the tests again to ensure it passes, and then refactor as necessary.
Popular TDD Frameworks
JUnit
JUnit is a widely used testing framework for Java applications. It provides annotations to identify test methods, assertions for testing expected outcomes, and a variety of tools for organizing and running tests.
PHPUnit
PHPUnit is a popular testing framework for PHP. It provides a simple and intuitive way to write and run tests for PHP applications.
NUnit
NUnit is a popular testing framework for .NET applications. It provides a clear and concise syntax for writing and running tests, including assertions for testing expected outcomes.
Pytest
Pytest is a popular testing framework for Python. It provides a clear and concise syntax for writing and running tests, including assertions for testing expected outcomes.
Behavior-Driven Development (BDD)
Behavioral-Driven Development (BDD) is a testing approach derived from the Test-Driven Development (TDD) methodology. In BDD, tests are mainly based on systems behavior. This approach defines various ways to develop a feature based on its behavior. In most cases, the Given-When-Then approach is used for writing test cases. Let’s take an example for a better understanding of TDD vs BDD:
Given the user has entered valid login credentials When a user clicks on the login button Then display the successful validation message As shown above, the behavior is illustrated in a very simple English language, a shared language. This helps everyone in the team responsible for development to understand the feature behavior.
Key benefits of BDD
- Helps reach a wider audience through the usage of non-technical language
- Focuses on how the system should behave from the customer’s and the developer’s perspective
- BDD is a cost-effective technique
- Reduces efforts needed to verify any post-deployment defects
How to perform BDD? Behavior-Driven Development (BDD) is a collaborative approach that bridges the gap between technical and non-technical stakeholders by using a shared language to define software behavior. This methodology emphasizes understanding requirements through examples and scenarios, enabling teams to develop features that align closely with user needs.
Below is a structured overview of the steps involved in BDD, along with descriptions and the stakeholders typically involved in each step.
| Step | Description | Stakeholders Involved |
|---|---|---|
| 1. Identify Features | Collaborate with stakeholders to identify and prioritize features or functionalities needed for the software. | Product Owners, Business Analysts, Developers, Testers |
| 2. Write Scenarios | Create user stories and define acceptance criteria in the form of scenarios. Use a common language to describe expected behavior. | Product Owners, Business Analysts, Developers, Testers |
| 3. Review Scenarios | Conduct reviews of the scenarios with all stakeholders to ensure clarity and shared understanding of the requirements. | Product Owners, Business Analysts, Developers, Testers |
| 4. Implement Code | Developers write code to implement the functionality described in the scenarios, ensuring that it meets the acceptance criteria. | Developers |
| 5. Write Automated Tests | Create automated tests based on the defined scenarios. This often involves using BDD frameworks (e.g., Cucumber, SpecFlow). | Developers, Testers |
| 6. Run Tests | Execute the automated tests to verify that the implemented functionality behaves as expected. | Developers, Testers |
| 7. Refactor Code | Optimize and clean the code, ensuring that it remains maintainable while retaining the functionality described in the scenarios. | Developers |
| 8. Repeat | Continue the BDD cycle for new features or modifications, incorporating feedback and new requirements as necessary. | All Stakeholders |
BDD Example
An example for BDD is given below
Step 1. Identify Features: Collaborate with stakeholders to determine the need for a user login feature for authentication and security.
Step 2. Write Scenarios: Create user stories and acceptance criteria; for example:
Successful Login: Given a registered user, when valid credentials are entered, then redirect to the dashboard. Unsuccessful Login: Given a registered user, when invalid credentials are entered, then display an error message. Step 3. Review Scenarios: Validate scenarios with stakeholders to ensure shared understanding of requirements.
Step 4. Implement Code: Develop the login functionality, including the UI and backend authentication logic.
Step 5. Write Automated Tests: Use a BDD framework (e.g., Cucumber) to create tests based on the written scenarios.
Step 6. Run Tests: Execute automated tests; refine the implementation if tests initially fail.
Step 7. Refactor Code: Improve code for efficiency and readability without changing functionality once tests pass.
Step 8. Repeat: Iterate for additional features or modifications, writing and reviewing new scenarios as needed.
This concise approach highlights the iterative and collaborative nature of BDD, focusing on behavior to effectively meet user needs and enhance software quality.
Popular BDD Frameworks
Cucumber
Cucumber is one of the most popular BDD frameworks, allowing users to write test scenarios in a natural language format (Gherkin). This makes it accessible to both technical and non-technical team members.
SpecFlow
SpecFlow is a BDD framework for .NET, providing a clear and concise syntax to define and execute test scenarios. It supports multiple programming languages, including C#, F#, and VB.
JBehave
JBehave is a BDD framework for Java, offering a simple and intuitive syntax for writing and executing test scenarios.
Behat
Behat is a BDD framework for PHP, providing a clear and concise syntax to define and execute test scenarios. It supports multiple programming languages, including PHP, Python, and Ruby.