Testing your software application before releasing it to the public is key to ensuring that your product meets quality standards.
There are several different ways to approach software testing, and the two most commonly applied are Test-Driven Development (TDD) and Behavior-Driven Development (BDD).
TDD focuses on writing automated tests before writing the actual code that needs to be tested. On the other hand, BDD emphasizes user behavior and defines software functionality in an accessible language for all stakeholders.
While both approaches play an important role in modern software development, there’s an ongoing debate about when to use TDD or BDD and which offers greater benefits.
In this quick guide, we’ll discuss test-driven development and behavior-driven development, including a clear breakdown of how they differ and complement each other and why they both matter. Let’s get started.
What is Test-Driven Development (TDD)?
Test-driven development is an iterative approach to development that involves writing automated tests prior to writing the code.
This gives developers the context they need to improve their code and is designed to offer continuous feedback so that bugs can be identified and fixed as soon as possible.
Benefits of TDD
- Detects bugs early, reducing the time spent on debugging and rework
- Encourages writing only the necessary code, preventing over-engineering
- Ensures the creation of flexible, maintainable, and easily refactorable code
- Increases productivity by minimizing unexpected issues during development
- Reduces overall project costs by avoiding defects and unnecessary revisions
- Acts as built-in documentation, making it easier to understand system functionality
- Allows all team members to collaborate effectively with a well-structured codebase
- Provides instant feedback through automated tests, speeding up development cycles
Cons of TDD
As we explore what TDD vs BDD looks like, it’s essential to be conscious of the cons that each has. TDD has its disadvantages as an approach, including:
- It can slow down initial development since tests must be written before the code for every function
- Faulty or poorly written tests can lead to incorrect implementations and false confidence in the code
- It may increase architectural complexity if the generated code does not align well with the overall system design
- Requires prior experience and discipline to implement effectively, making it challenging for teams unfamiliar with TDD
Top TDD Testing Tools
The right TDD testing tools are like a skilled craftsman’s kit, enabling you to build robust code with precision and ease. Here are our top picks:
1. Pytest
Pytest is a highly flexible Python framework that makes writing small, readable tests easy and can scale to support complex functional testing for apps and libraries. It promotes TDD principles through the auto-discovery of test modules and functions.
Pytest boasts a rich plugin architecture, with 1,300+ external plugins and a thriving community.
2. JUnit5
JUnit5 is a modern test automation framework for the Java programming language. It’s designed for developer-side testing on the JVM. It includes a Console Launcher, which allows tests to be executed from the command line, and the JUnit Platform Suite Engine, which enables the execution of custom test suites using multiple test engines.
JUnit 5 also seamlessly integrates with build tools like Gradle and Maven, making it a popular choice for TDD testing.
3. Mocha
Mocha is a feature-rich JavaScript test framework that runs on Node.js. It allows you to run tests serially, ensuring flexible and accurate reporting while mapping uncaught exceptions to the corresponding test cases.
Its dynamic and intuitive interface will enable developers to choose their DSL style, supporting BDD, TDD, Exports, QUnit, and Require-style interfaces.
4. Selenium
Selenium is an open-source software comprising various tools and libraries for automating web browsers. You can simulate user actions like typing, clicking, interacting, and navigating with the web elements to test how your apps behave across browsers like Chrome, Firefox, and Safari.
You can generate Extent Reports in Selenium, and with support for headless execution, Selenium facilitates early and frequent testing in a TDD workflow.
5. WebdriverIO
WebdriverIO is a browser and mobile automation test framework for Node.js. Built with TDD-friendly features, it automatically waits for elements to appear before interacting with them and offers cross-browser support via automation through WebDriver and WebDriver Bidi.
6. Mockito
Mockito is a mocking framework for Java that simplifies unit testing. It provides a clean and easy-to-use API, equipping developers to write readable tests with minimal effort. It also produces clear verification errors, making debugging easier.
Regarding TDD, Mockito enhances test readability and ensures alignment with business requirements.
How to Choose a TDD Test Automation Tool
- Since TDD relies on rapid test execution, choose a tool that runs unit tests in milliseconds to avoid slowing development
- TDD tools should be well-maintained and widely adopted, ensuring long-term support and troubleshooting resources
- TDD tools should match your tech stack, such as JUnit (Java), pytest (Python), and Jest (JavaScript), for seamless unit testing
- Fast debugging is key; select a tool that provides real-time logs, failure insights, and visual reports to speed up issue resolution
- Your tool should seamlessly integrate with your IDE (e.g., IntelliJ, VS Code) and build platforms (Maven, Gradle, npm) for a smooth workflow
- TDD requires isolating components; pick a tool that makes mocking dependencies easy (e.g., Mockito for Java, unittest.mock for Python)
- Since TDD encourages constant refactoring, choose a tool that reruns tests automatically and supports evolving codebases without breaking
Best Practices to Follow to Perform TDD Effectively
Here’s a step-by-step look at how the TDD process happens:
1. Create tests
The first step involves writing tests where your developers define exactly what behavior they expect out of a unit of code.
This includes specifying any dependencies, code parameters, and expected outputs. Depending on the individual case, the developer may want to write this test themselves or use automation tools to speed up the process.
2. Implement the code
Based on the test results, your developers start by writing just enough code to make the tests pass — nothing extra.
This “minimalistic” approach allows developers to focus on the most immediate requirements without wasting time over-engineering the app or optimizing too early.
3. Run and refactor
After the first set of code is written and it makes the tests pass, it’s time to run all the other tests. As always, your developers ensure that the old code’s functionality remains preserved with each test run.
Based on the test feedback, your developers refactor the code for better design and maintainability. This cycle continues until your app code is where you want it to be.
4. Start with one test
You kick off the TDD by running one test and watching it fail. And yes, it will fail at this stage — since no code has been developed yet. So why do it, you might ask? There are actually several reasons:
- It ensures that your testing environment is correctly set up
- It serves as an objective that the developer keeps in mind as they code the feature
- It verifies that the test is properly checking the behavior associated with the piece of code in question
- Once the code is implemented, it provides immediate feedback on code accuracy so that developers can fix things right away
For optimum results, we recommend picking a test with a small scope that focuses on the main requirements of the feature in question.
For example, if the feature is user account creation, the test could check whether a user object is successfully created in the system. This test will fail initially since no ‘user.create’ method exists. The developer will then implement just enough code to make it pass.
What is Behavior-Driven Development (BDD)?
Behavior-driven development is a testing approach that defines various methods to develop an application feature based on its behavior.
The emphasis is on defining the behavior in simple everyday language so that everyone on the team can understand the feature (including non-technical team members). For instance, if the feature involves confirming a successful user login, BDD will define it as follows:
- Given the user has entered a valid username and password,
- When the user clicks the “Login” button,
- Then, the system should display a “Login Successful” message.
- This is an example of the “Given-When-Then” framework — one of many used to express feature behavior in the BDD approach.
Benefits of BDD
When comparing TDD vs BDD, the main benefit of BDD that one can instantly appreciate is its accessibility. Anyone can understand what the feature in question tries to do, making for a simpler testing process. Other advantages include:
- It is more cost-effective, as both technical and non-technical team members can write test scenarios
- Simplifies the development process by making test cases easy to understand and maintain
- Focuses on user perspective as well as clear developer instructions when designing tests
- Reduces the time needed to identify defects or deviations from expected behavior
- It can be executed both manually and automatically, offering flexibility in testing
- Each scenario serves as a self-documenting test case for future reference
- Ensures each test has a well-defined purpose and expected outcome
Cons of BDD
The disadvantages of BDD include:
- Lack of involvement from product owners can result in tests that don’t accurately reflect real-life user behavior
- Poorly written tests can be either too vague or too specific, reducing their effectiveness
- Ineffective automation can lead to inconsistencies and delays in test execution
- It is difficult to run tests in parallel, as each test requires a separate feature file
- Incorrect syntax in test scenarios can lead to confusion and errors
Top BDD Testing Tools
You need the right BDD testing tool to boost collaboration and drive test automation via clear specifications. Here are a few options that can help.
1. Behat
Behat is an open-source BDD framework for PHP. It enables developers to define executable specifications in a structured, human-readable format, ensuring alignment between technical implementation and business expectations.
Built on Symfony components, Behat follows strict coding standards and scores high in static analysis tools.
2. JBehave
JBehave is a BDD framework for Java that enables test scenarios to be written in a human-readable format using the “Given-When-Then” structure.
It allows developers to define executable specifications that guide TDD while ensuring clear communication between technical and non-technical stakeholders.
3. FitNesse
Think of FitNesse as a communication-first TDD testing tool. It’s a wiki web server with a low entry and learning curve. It supports acceptance testing and facilitates collaboration between developers, testers, and business stakeholders.
It helps execute test scenarios written in a tabular format.
4. Gauge
Gauge is an open-source test automation framework that helps create readable and maintainable tests. It minimizes duplication by allowing reusable specifications and robust refactoring. Gauge works with multiple languages, CI/CD tools, and automation drivers.
You can also easily extend Gauge to add support for IDEs, drivers, and data sources.
5. BeanSpec
BeanSpec is a Java-based BDD tool for Java IDEs like NetBeans and Eclipse. It employs declarative language to specify, check, and summarize complex component behavior, which is apt for defining behavior-driven tests.
An internal reporting feature generates reports at the end of the test execution runs.
6. Cucumber
Cucumber is an open-source BDD testing tool. Initially written in Ruby, it now supports programming languages like Java and JavaScript. It uses Gherkin keywords (Given, When, Then) to write test scenarios.
It also easily integrates with other testing frameworks like JUnit and TestNG to ease the incorporation of BDD into existing environments.
How to Choose a BDD Test Automation Tool
- Since BDD is designed for collaboration, pick a tool that supports Gherkin syntax (Given-When-Then), so both technical and business teams can contribute
- Since BDD vs. TDD involves more collaboration, choose a well-supported tool with active development, plugins, and community support to ensure longevity
- A strong BDD vs. TDD advantage is reusability; choose a tool that allows you to reuse step definitions across multiple test cases, reducing redundancy Your BDD tool should work well with test automation frameworks like Selenium, Cypress, and Appium to execute behavior-driven tests efficiently If your application must run on multiple browsers, devices, or operating systems, your BDD tool should support diverse test environments Unlike TDD tools, BDD tools need business-readable reports; look for something that generates clear, shareable, and visual test reports
Best Practices to Follow to Perform BDD Effectively
Here’s a breakdown of the basic steps involved in BDD testing:
1. Identify features to be tested
This is the first critical step and calls for collaboration with all relevant stakeholders, including product managers, developers, testers, and business analysts. You want to ensure that you are testing the features that real-life users prioritize the most.
2. Write out scenarios
Prepare your testing scenarios for each feature, including acceptance criteria and user stories. Use language and syntax that everyone understands. Then, review them with your stakeholders to ensure their relevance and adherence to the requirements.
3. Create code
Have your developers write the necessary code for the functionality described in each user scenario. It should align with the business logic and meet the acceptance criteria.
4. Prepare and run tests
Use BDD frameworks (e.g., Cucumber, Behave, SpecFlow) to implement automated tests based on the user scenarios. Run them to validate whether the implemented functionality meets the expected behavior. If any tests fail, your developers must address issues and rerun the tests.
5. Refactor and repeat
Based on the test results, have your developers optimize the code while preserving all essential user functionality.
Then, rerun the tests as needed until you have the results your stakeholders seek. Confirm no unintended changes break existing features and repeat the process for each new feature or change.
Does BDD Enhance TDD?
Yes, but it’s essential not to get too fixated on the TDD vs BDD comparison. Indeed, both methodologies work side by side to make software development easier.
Here’s how BDD works to enhance TDD:
1. Better understanding among stakeholders
BDD helps ensure that every project’s requirements are laid out in plain language, allowing technical and non-technical stakeholders to work together. Having everyone’s insights helps to build more comprehensive TDD tests that capture real-world user needs.
2. Better test coverage
BDD ensures that multiple user scenarios are laid out upfront, reflecting how real-life people think and respond when they use an app. This helps develop TDD tests with a more comprehensive range and meet user expectations rather than just checking for code accuracy.
3. Keeping functionality intact
BDD scenarios allow developers to define the user features that need to remain intact while refactoring the code for upgrades. This ensures that the user experience your audience knows and loves is not impacted.
Final Words
By now, you might be asking yourself: “In the TDD vs BDD debate, which should I opt for when developing my app?” The answer — you need both.
TDD gives you the advantage of fast, almost instantaneous feedback on your code, while BDD gives you the human perspective you need to design apps your users will love.
Encourage your software team to embrace the best of both as they plan their development projects. There are tools galore on the market to help with each — make the investment, and you’ll see the difference before you know it.
Source: For more details, readers may refer to TestGrid.
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