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Test-Driven and Behavior-Driven Development at ScienceSoft
With 35 years of experience in software development and an in-house project management office (PMO), ScienceSoft engineers robust and user-centric software solutions that adhere to the highest quality standards. Focused on delivering quality results within the existing time and budget constraints, we keep our testing strategies flexible, integrating TDD and BDD based on each project’s needs.
Why we selectively apply TDD and BDD
While TDD and BDD can boost software quality, they also require extra time and resources. Through our experience with over 3,000 software projects, we've found that prioritizing quality alone rarely aligns with our clients’ needs. Typically, they require a balance of quality, speed, cost-effectiveness, simplicity, maintainability, and other unique factors.
Thus, we train our teams in TDD and BDD but don't apply them in every project by default. Instead, we tailor our approach based on each project's constraints, choosing development and QA strategies that best fit the situation. This may mean foregoing TDD and BDD in favor of more time-saving strategies, including rapid prototyping, static analysis tools and CI/CD pipelines, and test automation.
Test-Driven Development: Pros, Cons and Alternatives
Test-Driven Development (TDD) is a software development approach where tests are written before the actual code is implemented. Primarily used for unit testing, TDD follows the Red-Green-Refactor cycle, which promotes small, incremental changes. The developer writes a failing test for new functionality, then writes minimal code to pass the test and subsequently refactors the code to improve its structure without altering its behavior, ensuring it still passes all tests.
How TDD increases software quality
Focus on requirements
Writing tests first compels developers to think critically about the desired software behavior before implementation. It helps them clarify requirements early, cover edge cases comprehensively, prioritize current user needs, and prevent unnecessary complexity in the software functionality.
Comprehensive living documentation
Unlike post-development unit tests, TDD tests better reflect the intended use and edge cases since they are integral to the design process. Thus, TDD tests often serve as living documentation, making it easier for new team members to understand the system and for existing members to recall the purpose of specific code sections.
Immediate feedback
Since tests are written before the code in TDD, developers get immediate feedback on whether the new code meets the requirements. This helps catch errors early in the development process and reduces debugging time.
Streamlined refactoring
The presence of a comprehensive suite of granular tests allows developers to refactor code with confidence, knowing that any unintended changes in behavior will be caught by the tests.
Improved software design
TDD encourages modular and loosely coupled code, as writing tests for tightly coupled components can be challenging. This results in better software architecture, cleaner code, and easier maintenance.
Key challenges and limitations of TDD
Increased development time
Writing tests before implementing functionality can slow down the coding process. This might cause delays, especially in fast-paced or time-constrained projects.
Increased costs
TDD may require significant time and resources to create and maintain comprehensive test suites. For projects with tight deadlines or limited budgets, this investment might not be feasible.
Overemphasis on unit tests
TDD often prioritizes unit tests, potentially leading to neglect of integration, system, or acceptance testing. This can create a false sense of security if only unit-level functionality is thoroughly tested.
Risks of over-engineering
Developers might over-engineer solutions to pass all possible tests, resulting in unnecessarily complex code.
Not always practical
In projects where requirements are fluid and exploratory development is required (e.g., for complex data analytics platforms, blockchain solutions, or innovative mobile app interfaces), it may not be feasible to define accurate tests before implementation.
Where we may apply TDD:
- Large projects that require exceptional reliability, such as those in the finance, healthcare, or aerospace domains. TDD helps ensure that the system behaves correctly under any conditions.
- Large projects that involve intricate business rules (e.g., tax and accounting software). TDD helps capture all edge cases and ensures their correct implementation from the start.
Alternative approaches for when we can’t use TDD:
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Following coding standards and conducting comprehensive unit testing to enforce the same level of design discipline as TDD. Writing unit tests at different stages (before, during, or after coding) allows for more flexibility compared to TDD’s rigid test-first approach. This adaptability not only accommodates different project timelines and developer workflows but also fosters a more iterative and responsive development environment. |
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Using static analysis tools and implementing CI/CD pipelines to ensure that tests run automatically and consistently, providing rapid feedback similar to TDD’s fast iteration cycles. |
Behavior-Driven Development: Pros, Cons, and Alternatives
Behavior-driven development (BDD) is a software development approach that extends TDD by focusing on the application's behavior from the user's perspective. It uses Given-When-Then scenarios in plain language (natural languages, Gherkin language, or custom domain-specific languages) to ensure a shared understanding among developers, testers, and non-technical stakeholders.
See an example of a Given-When-Then scenario for an ecommerce app
Adding different items to the cart
- Given the shopping cart is empty.
- When the user adds a "Green Hat" to the cart.
- And the user adds a "Yellow Scarf" to the cart.
- Then the shopping cart should display "2 items."
- And the total price should be the sum of the prices for the "Green Hat" and "Yellow Scarf."
We keep BDD scenarios concise, usually with no more than 10 steps, to ensure clarity and maintainability.
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How BDD increases software quality
Focus on value to end users
In BDD, the development process depends on user stories that are converted into scenarios using natural language. This fosters collaboration among developers, testers, product owners, and stakeholders that can all smoothly communicate about user needs and behavior-focused requirements.
Scenarios serve as living documentation and automated tests
BDD scenarios provide clear descriptions of requirements and serve as living documentation that stays relevant and up-to-date as the application evolves. They are also written in a way that can be automated by tools like Cucumber and SpecFlow, linking them to executable test code.
Early detection of issues
Just like TDD, BDD promotes writing tests before implementing features. This approach helps identify potential issues early in the development process, reducing the cost and effort required for later fixes.
Modular and reusable code components
When behaviors are clearly specified, developers are encouraged to encapsulate specific functionalities within distinct modules or components with minimal dependencies on each other. Each component is responsible for a particular behavior, making it easier to isolate, test, and reuse.
Key challenges and limitations of BDD
Time-consuming process
Writing detailed scenarios and ensuring they cover all edge cases slows down the initial phases of development, especially in projects with complex business logic.
Maintenance overhead
Maintaining a large number of scenarios can become cumbersome.
Risk of over-specification
Rigid, detailed tests can hinder flexibility and adaptability to change.
Not suitable for all projects
BDD is not practical for projects with highly technical requirements, such as back-end services or infrastructure projects. Also, translating complex business logic into Gherkin can lead to oversimplification or convoluted scenarios that are hard to maintain.
Where we may apply BDD:
- Projects where user experience and satisfaction are critical, such as ecommerce platforms or consumer mobile apps. BDD helps focus on user stories and expected behaviors, ensuring the final software solution meets user needs.
- Projects that involve intricate business rules and processes (e.g., insurance software and SCM systems). BDD helps bridge the gap between technical and non-technical team members.
Alternative approaches for when we can’t use BDD:
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Establishing effective direct communication with different groups of stakeholders to gather requirements, clarify expectations through regular interactions, and conduct usability testing. This streamlines stakeholder alignment without the need for BDD's formal approach. |
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Mapping user stories to visualize user journeys and prioritize features that deliver real value, aligning with BDD's focus on user scenarios. |
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Proactively creating prototypes and iterating rapidly based on user feedback to validate ideas quickly and make necessary adjustments to meet user expectations. This approach is consistent with BDD's user-centric nature but is achieved through direct user interactions with the software rather than formal specifications. |
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Extensively using automated UI testing written in a style similar to BDD. This guarantees that functionality corresponds to the requirements while keeping the tests highly readable. |
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Prioritizing component-based architectures like microservices or frameworks like React by default. This supports reusability and scalability without needing BDD's influence. |
Tools and Technologies We Use for TDD and BDD
Real Results: How Our Software Solutions Meet and Exceed Expectations
We know we can always rely on ScienceSoft's various competencies when our clients require quality software which would facilitate their business success.
The quality they deliver is consistently high. With ScienceSoft, we managed to acquire the development resources that we needed and got them fit into our teamwork smoothly. We believe they've contributed a lot to speed up our product's release.
ScienceSoft professional and knowledgeable staff has the willingness to endeavor best efforts to ensure project success. Every aspect of development is always handled with consideration and care. What we are especially impressed with is the high quality of the deliverables.
