What makes a software requirement testable?

1 Benefits of testable requirements

Testable requirements have many advantages for software engineering. They help you avoid ambiguity, confusion, and errors that can lead to costly rework, delays, or failures. They also help you communicate your expectations and assumptions to other stakeholders, such as developers, testers, customers, or users. Testable requirements also enable you to measure the progress and quality of your software, as you can compare the actual results with the expected ones. Testable requirements can also facilitate the design, implementation, and maintenance of your software, as they provide clear and consistent guidance for your decisions and actions.

3 Examples of testable requirements

To illustrate how to write testable requirements, let's look at some examples. Suppose you are developing a web application that allows users to create and share online surveys. Here are some possible requirements and how they can be made more testable: Instead of saying the application should be user-friendly, it should have a simple and intuitive user interface, with clear labels, instructions, and feedback. Furthermore, it should comply with the web accessibility standards and guidelines, as well as have a response time of less than 3 seconds for each user action. As for allowing users to create surveys, the application should provide a survey creation tool that enables them to define the survey title, description, questions, and options. It should also validate the survey data and prevent incomplete or invalid surveys from being saved or published, while generating a unique URL for each survey that can be copied or shared by the user. Lastly, the application should record and store the responses of each survey participant in a secure database. It should display the number of responses and the completion rate for each survey on the user dashboard, with an option to export the survey data in CSV or PDF formats.

4 Best practices for testable requirements

Writing testable requirements is not always easy, but it can be improved with some best practices and techniques. To that end, you should use clear and concise language, avoiding jargon, acronyms, or technical terms. Additionally, use active voice and imperative mood to state what the software must or must not do. Furthermore, use precise and quantifiable terms such as numbers, percentages, ranges, or units rather than subjective or relative terms. Additionally, you can use scenarios, examples, or diagrams to illustrate complex or abstract concepts or features. Moreover, test cases, checklists, or criteria can be used to define how the requirements will be verified or validated and what the expected outcomes or results will be. Lastly, it is important to review and revise the requirements regularly to check for consistency, completeness, accuracy, and relevance while resolving any conflicts, gaps, or ambiguities.

5 Challenges of testable requirements

Writing testable requirements is not without its challenges. Over-specifying or under-specifying the requirements, assuming or omitting important information, failing to consider the user's perspective, neglecting non-functional requirements, and changing or evolving the requirements without updating the relevant stakeholders can all be pitfalls. Too much or too little detail, unnecessary or unrealistic constraints, omitting context, assumptions, dependencies, or risks, ignoring feedback from stakeholders, and not accounting for usability, security, reliability, or scalability can all impact the software's functionality and performance. It is important to consider user needs and preferences as well as business needs and market conditions when writing testable requirements.