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Wednesday, January 7, 2009

How to test software requirements specification (SRS)?

Do you know “Most of the bugs in software are due to incomplete or inaccurate functional requirements?” The software code, doesn’t matter how well it’s written, can’t do anything if there are ambiguities in requirements.

It’s better to catch the requirement ambiguities and fix them in early development life cycle. Cost of fixing the bug after completion of development or product release is too high. So it’s important to have requirement analysis and catch these incorrect requirements before design specifications and project implementation phases of SDLC.

How to measure functional software requirement specification (SRS) documents?
Well, we need to define some standard tests to measure the requirements. Once each requirement is passed through these tests you can evaluate and freeze the functional requirements.

Let’s take an example. You are working on a web based application. Requirement is as follows:
“Web application should be able to serve the user queries as early as possible”

How will you freeze the requirement in this case?
What will be your requirement satisfaction criteria? To get the answer, ask this question to stakeholders: How much response time is ok for you?
If they say, we will accept the response if it’s within 2 seconds, then this is your requirement measure. Freeze this requirement and carry the same procedure for next requirement.

We just learned how to measure the requirements and freeze those in design, implementation and testing phases.

Now let’s take other example. I was working on a web based project. Client (stakeholders) specified the project requirements for initial phase of the project development. My manager circulated all the requirements in the team for review. When we started discussion on these requirements, we were just shocked! Everyone was having his or her own conception about the requirements. We found lot of ambiguities in the ‘terms’ specified in requirement documents, which later on sent to client for review/clarification.

Client used many ambiguous terms, which were having many different meanings, making it difficult to analyze the exact meaning. The next version of the requirement doc from client was clear enough to freeze for design phase.

From this example we learned “Requirements should be clear and consistent”

Next criteria for testing the requirements specification is “Discover missing requirements”

Many times project designers don’t get clear idea about specific modules and they simply assume some requirements while design phase. Any requirement should not be based on assumptions. Requirements should be complete, covering each and every aspect of the system under development.

Specifications should state both type of requirements i.e. what system should do and what should not.

Generally I use my own method to uncover the unspecified requirements. When I read the software requirements specification document (SRS), I note down my own understanding of the requirements that are specified, plus other requirements SRS document should supposed to cover. This helps me to ask the questions about unspecified requirements making it clearer.

For checking the requirements completeness, divide requirements in three sections, ‘Must implement’ requirements, requirements those are not specified but are ‘assumed’ and third type is ‘imagination’ type of requirements. Check if all type of requirements are addressed before software design phase.

Check if the requirements are related to the project goal.
Some times stakeholders have their own expertise, which they expect to come in system under development. They don’t think if that requirement is relevant to project in hand. Make sure to identify such requirements. Try to avoid the irrelevant requirements in first phase of the project development cycle. If not possible ask the questions to stakeholders: why you want to implement this specific requirement? This will describe the particular requirement in detail making it easier for designing the system considering the future scope.

But how to decide the requirements are relevant or not?
Simple answer: Set the project goal and ask this question: If not implementing this requirement will cause any problem achieving our specified goal? If not, then this is irrelevant requirement. Ask the stakeholders if they really want to implement these types of requirements.

In short requirements specification (SRS) doc should address following:
Project functionality (What should be done and what should not)
Software, Hardware interfaces and user interface
System Correctness, Security and performance criteria
Implementation issues (risks) if any

I have covered all aspects of requirement measurement. To be specific about requirements, I will summarize requirement testing in one sentence:
“Requirements should be clear and specific with no uncertainty, requirements should be measurable in terms of specific values, requirements should be testable having some evaluation criteria for each requirement, and requirements should be complete, without any contradictions”

Testing should start at requirement phase to avoid further requirement related bugs. Communicate more and more with your stakeholder to clarify all the requirements before starting project design and implementation.

Do you have any experience testing software requirements?

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