In the world of software development, the creation of innovative, leading and user-centric applications does not just depend on the quality of coding or the complexities of technologies employed. At the heart of successful software deliveries lies the often-underappreciated phase of requirements gathering—a very important process that should significantly increase the effectiveness and overall success of the project. The importance of writing great requirements cannot be overstated. It serves as the primary layer upon which, lay all subsequent phases of development. It influences the project's journey from conception to deployment and beyond.

Great requirements guide the development team through the complex journey of bringing a software product to life. They provide a shared acknowledgement of what should be built and why. This clarity is invaluable for aligning the expertise within a development team, guaranteeing that everyone from developers, designers, testers and project managers, is moving together towards a common goal. Without this alignment, projects are highly likely to suffer miscommunication and scope creep — pitfalls that can massively derail timelines, inflate budgets, and compromise the quality of the final product.

With a solid set of approved product requirements, you have a bridge between the stakeholders' expectations and the technical team's delivery. They translate complex needs, wants, and constraints of users and stakeholders into a language that developers and testers can understand and act upon. This translation is crucial for establishing that the software meets the expectations of its intended users, delivering great value. In a landscape where user satisfaction is paramount, and competition fierce, the ability to accurately capture and implement user requirements can distinguish successful projects from those that falter.

By thoroughly understanding and documenting what needs to be achieved before any code is written, teams can anticipate challenges, plan resources more effectively, and make informed decisions that steer the project towards success. This foresight reduces the likelihood of costly reworks, delays, and feature bloat, which can erode stakeholder trust and user satisfaction.

In addition to their immediate benefits in the initial development process, well-crafted requirements and acceptance criteria are hugely important for the maintainability and scalability of the software over time. They provide a documented history of the project's objectives and decisions, which is invaluable for future enhancement, troubleshooting, and adaptation efforts. As software inevitably evolves to meet new user needs or technological advancements, having a solid foundation of original requirements makes it easier to assess the impact of changes and helps to make sure that the software continues to align with its core purpose and user expectations. Thorough regression testing of existing features requires close alignment to original source requirements to confirm that nothing has regressed as new features are rolled out to customers.

Why Should Requirements be Singular and Unambiguous?

The principle of ensuring that requirements are singular in nature is rooted in the goal of achieving clarity, precision and simplicity in the specification of what a software system should do. This practice is vital for several reasons, each contributing to the overall success and manageability of the software development process.

Clarity and Understandability

When a requirement is singular, it focuses on one specific aspect or feature of the software. This singularity makes it easier for all stakeholders, including developers, testers, project managers and clients, to understand what is expected without ambiguity. Requirements that try to address multiple functionalities or objectives at once can lead to confusion, misinterpretation, and differing expectations among team members and stakeholders.

Simplifies Verification and Validation

A continual process in software development is testing (verifying and validating) that the software meets all defined requirements. When each requirement describes a single, discrete function, it becomes significantly easier to test and verify that requirement. This straightforward approach allows for more effective testing, ensuring that each requirement can be conclusively marked as met or not met.

Facilitates Accurate Estimation and Planning

Software projects often suffer from inaccurate delivery estimates, leading to delays and budget overruns. Singular requirements contribute to more precise estimation of time and resources needed because they allow for a focused assessment of each individual requirement. Project managers, developers and testers can more accurately estimate the effort, time, and resources needed to implement and test each requirement when they do not have to untangle complex, multi-faceted requirements.

Eases Prioritization and Scope Management

Singular requirements simplify the process of prioritizing features and managing the project backlog. It becomes easier to assess the importance and impact of each requirement independently, facilitating discussions around prioritization and potential scope adjustments. This clarity is crucial in agile environments, where flexibility and adaptability are key, allowing teams to make informed decisions about what to work on next based on well-defined, singular requirements supported with a strong business case.

Improves Traceability

In software development, traceability refers to the ability to link delivered functionality back to a well crafted user story or requirement. Singular requirements improve traceability by providing a clear, unambiguous reference point for each feature throughout the development lifecycle, from design through testing to deployment. This traceability is essential for maintaining alignment with the project's goals, managing changes, and ensuring compliance with external regulations or standards.

Supports Effective Change Management

Changes are inevitable in software development. Singular requirements ease the management of these changes because the impact of modifying, adding, or removing a requirement is clearer when each requirement is focused on a single aspect. This clarity supports more effective assessment of the implications of changes, helping teams to adapt more effectively while minimizing disruptions and risk to the project.

Reduces Development Costs

Ambiguities in requirements can lead to significant rework, as features may need to be redesigned, recoded, and retested until they meet the stakeholder's expectations. This rework is not only time-consuming but also expensive, driving up the overall cost of the project. Clear and unambiguous requirements reduce the need for rework, helping to keep development costs under control.

Enhances Customer Satisfaction

Ultimately, the goal of any software project is to deliver a product that meets or exceeds customer expectations. Unambiguous requirements are critical to achieving this goal, as they ensure that the software developed aligns with the marketing team’s product promotion and the customer's needs. This alignment is key to delivering value to the customer, fostering satisfaction and building long-term relationships alongside brand loyalty.

How Can You Make Sure a Requirement is Testable?

Testability refers to the ability to empirically validate a requirement through testing, demonstrating that the software meets the specified criteria. A testable requirement allows project teams to objectively assess the software's functionality or performance against defined expectations. Here are strategies to ensure that requirements are testable:

Define Clear Acceptance Criteria

The foundation of a testable requirement is the presence of clear, specific, and measurable acceptance criteria. These criteria delineate the conditions under which a requirement is considered met. By defining these conditions upfront, you provide a concrete basis for testing and measuring success. Acceptance criteria should explain clearly what the system should do and under what conditions, with quantifiable metrics where applicable.

Use Specific, Unambiguous Language

Avoid vague terms and generalities that can lead to multiple interpretations. Phrases like “user-friendly,” “fast,” or “efficient” are subjective and do not provide a clear basis for testing. Instead, use precise, unambiguous language and, where possible, quantify expectations (e.g., “The system shall process transactions within 2 seconds under normal operating conditions”).

Incorporate Performance and Quality Attributes

Requirements should not only specify what the system should do (functional requirements) but also how well it should do it (non-functional requirements), including performance, usability, security, and compatibility criteria. These attributes should be explicitly defined in a way that can be measured and tested (e.g., “The system shall support 100 concurrent users without performance degradation”).

Ensure Independence

A testable requirement should be independent and not rely on the outcome of another requirement for its validation. This independence simplifies the testing process by allowing each requirement to be tested in isolation, reducing complexity and eliminating dependencies that can complicate test execution.

Employ Use Cases and User Stories

Use cases and user stories can help frame requirements in a real-world context, providing a narrative that describes how different users will interact with the system to achieve specific goals. These narratives can help identify necessary test scenarios and ensure that requirements are grounded in actual user needs and behaviors.

Iterative Review and Refinement

Developing testable requirements is an iterative process that benefits from continuous review and refinement. Engage stakeholders, developers, and testers in regular reviews of the requirements to identify ambiguities and refine the specifications. This collaboration can uncover issues early and ensure that the requirements are both accurate and testable. As a process, this can also be referred to as ‘testing the requirements’ themselves.

Leverage Modelling Techniques

Models, diagrams, and prototypes can provide a visual representation of requirements, offering an additional layer of clarity. These tools can help stakeholders and development teams understand complex requirements and interactions within the system, facilitating the identification of test conditions and criteria.

Plan for Testability from the Start

Incorporate testability as a criterion during the requirements gathering and specification phase, not as an afterthought. By considering how each requirement will be tested while it’s being defined, you can ensure that the requirement is formulated in a way that lends itself to effective testing.

Worth exploring:8 Software Quality Management Best Practices

How can BDD Help With Drafting Good Requirements?

Behavior-Driven Development (BDD) is an agile software development process that encourages collaboration among developers, quality assurance teams, and non-technical stakeholders (such as business analysts) in a software project. BDD focuses on obtaining a clear understanding of desired software behavior through discussion with stakeholders. It emphasizes the use of a simple, domain-specific language to describe the behavior of an application in terms of its input, its action, and the expected outcome. Here’s how BDD can help with drafting good requirements:

Encourages Clear, Concise, and Understandable Requirements

BDD uses a natural language style, often English, structured around the given-when-then (GWT) format to describe the behavior of the system. This approach makes requirements easier to understand for all stakeholders, regardless of their technical expertise. By writing requirements in the form of user stories that include scenarios or examples, BDD ensures that the requirements are specific, clear, and concise. Each scenario clearly defines the context (Given), the action (When), and the expected outcome (Then), providing a precise and unambiguous specification of the requirement.

Facilitates Collaboration

BDD fosters close collaboration between technical and non-technical stakeholders. This collaboration helps in capturing the requirements in a way that is understood by all parties. By engaging stakeholders in conversations about the desired behavior of the system, BDD ensures that the requirements reflect the actual business needs and user expectations.

Improves Requirements Validation

Through the use of executable specifications (scenarios written in the GWT format), BDD allows the validation of requirements before the development begins. These specifications serve as a living documentation and a basis for test cases. This approach helps in identifying any misunderstanding or miscommunication regarding the requirements at an early stage, ensuring that the development team builds the right feature.

Supports Continuous Feedback

BDD's emphasis on continuous examples and scenarios allows for ongoing refinement of requirements. As the project progresses, new scenarios can be added, and existing ones can be modified to reflect changes in understanding or requirements. This iterative process supports continuous feedback and adjustment, ensuring that the software evolves to meet the stakeholders' needs accurately.

Ensures Testability of Requirements

Since BDD, done correctly, inherently involves specifying desired behaviors as scenarios that can be automated, it should guarantee that requirements are testable from the outset. The given-when-then format naturally lends itself to the creation of test cases, making it easier to verify that the software meets the specified criteria. This alignment between requirements and testing improves the quality of the software and reduces the likelihood of defects.

Promotes a User-Centric Approach

BDD places the user's needs and behaviors at the forefront of the development process. By focusing on user stories and real-world scenarios, BDD ensures that the software is developed with the end user in mind. This user-centric approach helps in creating software that not only meets technical specifications but also delivers value to the target customers.

To sum up

So in your next stakeholder meeting or backlog prioritisation session, why not take some time to review these suggestions and see how you can begin to make your requirements gathering process and delivery more robust. It’s the simple things, done right, from the earliest stage that can have a dramatic influence on whether or not your delivery concludes successfully. It also sets you up with a series of strong new habits to take into your next project.

Let’s wrap up with a good and a not so good BDD scenario following our own advice. The examples have been exaggerated for dramatic effect!!

Bad

Feature: Online Store Checkout Process

As a regular shopper I want to be able to sort of go through some steps, you know, to buy things from the website

So that I might eventually get something I kind of want, if it all works out

Scenario: Buying an item, maybe

Given I've been browsing around on this website for ages and have probably put a bunch of stuff in my cart, or maybe not, who knows

And I think I'm logged in, or maybe I'm using a guest account, or perhaps I've forgotten my password again

When I decide I might try to buy something, if I feel like it

And I sort of attempt to navigate to the checkout, if I don't get distracted

Then I guess I should somehow, eventually, be able to provide some kind of information, or not, depending on what the site asks for

And maybe I'll get to a confirmation page, or maybe I'll just end up somewhere else entirely, it's really hard to say

But hopefully, I'll have bought something, assuming nothing goes too wrong and if I remember to actually confirm the purchase

And in the end, it would be nice if I got an email or something, but only if it's not too much trouble

​​

This example is intentionally crafted to highlight what to avoid:

1. Verbosity: The scenario is filled with excessive and unnecessary words, making it difficult to discern the core actions and expected outcomes.

2. Ambiguity: The steps are unclear and filled with indecisive language like "maybe," "sort of," and "or not, depending on." This makes it impossible to define clear test criteria.

3. Non-measurable Outcomes: The outcomes are vague, like "I guess I should somehow, eventually," which doesn't provide a concrete result or a way to measure success or failure.

Good

Feature: eCommerce Checkout

In order to purchase items efficiently

As a logged-in customer

I want to complete the checkout process smoothly and receive an order confirmation

Background:

Given I am a registered customer

And I am logged in to my account

Scenario: Successful checkout with saved payment method

Given I have added a product to my cart

When I complete my checkout with my saved payment method

Then I should see an order confirmation page with a unique order ID

And an email confirmation should be sent to my registered email address

Key Improvements Made:

1. Clarity and Precision: Each step is articulated clearly, specifying the exact actions to be taken and the expected outcomes, leaving no room for ambiguity.

2. Conciseness: The scenario is described succinctly, focusing only on the essential steps necessary for completing the checkout process and receiving an order confirmation.

3. Measurable Outcomes: The outcomes are specific and measurable, such as seeing an order confirmation page with a unique order ID and receiving an email confirmation, which can be easily verified during testing.

This BDD scenario effectively communicates the desired customer experience during the checkout process, making it an excellent tool for developers and testers to ensure the functionality meets the specified requirements.