INVEST Principle

INVEST is a mnemonic designed to outline the characteristics of a high quality requirement. While primarily targeted to software development projects, the INVEST principle can be applied to projects of all types. Each letter of the mnemonic is a criteria used to help a team assess the quality of a requirement.

INVEST stands for:

• I: Independent
• N: Negotiable
• V: Valuable
• E: Estimable
• S: Small
• T: Testable

Independent

Requirements should be as independent from one another as possible to avoid any complications in the prioritization or planning processes that could arise from overlapping scope. Dependencies could also lead to a domino effect of changes and adjustments if one aspect of multiple requirements should change.

Negotiable

Requirements should not be a closed contract. The team members should feel able and encouraged to collaborate and negotiate on solutions to the requirements given. Since the work performed to achieve the desired outcome is not known at the time of defining the requirement, it is possible that changes in scope will be recommended before work begins or as adjacent work completes and more is known. Negotiable requirements do not require rewriting since they allow for this flexibility.

Valuable

Every requirement should provide discernable value to the business. If it is not possible to find a statement of value for the feature, the team should consider whether the feature is necessary to implement.

Estimable

A big component of project management is estimating the scope of requirements for effective prioritization and to ensure milestones can be met. If the scope of work is unclear or ambiguous, the team cannot effectively estimate the amount of effort required to complete it or prioritize it. A delicate balance must be struck in removing ambiguity while simultaneously ensuring that a requirement is still negotiable.

Small

Requirements should be small both in terms of complexity and in their description. Having a small requirement can also help support other areas of INVEST, such as estimable, valuable, and testable (e.g. it's easier to estimate small requirements, it's clear whether or not value is presented if the scope is small, test criteria is clear, etc.)

Testable

A testable definition of done should be provided to confirm whether or not the requirement is complete. This should include clear actionable criteria that a feature can be measured against. Testable requirements are also easier to estimate, since the path to success can more simply be defined.

References

[1] “What Does Agile INVEST stand for?”, Wrike. [Online]. Available:  https://www.wrike.com/agile-guide/faq/what-does-agile-invest-stand-for/. [Accessed: 15-Feb-2023].

[2] “New to Agile? INVEST in good user stories”, Agile For All, 14-05-2009. [Online]. Available:  https://agileforall.com/new-to-agile-invest-in-good-user-stories/. [Accessed: 15-Feb-2023].