Verification and Validation: Building the Right Thing Right

· 4 min read
engineering best-practices software-development systems-engineering

If you’ve spent any time around systems engineers, you’ve probably heard the terms “verification” and “validation” thrown around with an almost religious reverence. To the uninitiated, they sound interchangeable. They’re not, and understanding the difference can save you from building something that works perfectly but solves the wrong problem.

The Classic Definitions

The systems engineering community has a wonderfully succinct way of distinguishing these two concepts:

Verification asks: “Did we build the thing right?”

Validation asks: “Did we build the right thing?”

Verification is about confirming that your product meets its specified requirements. It’s inward-looking, checking that the implementation matches the specification. If the spec says the button should be blue, verification confirms the button is blue.

Validation is about confirming that the product actually fulfills its intended purpose in the real world. It’s outward-looking, checking that what you built actually solves the problem you set out to solve. It asks whether anyone actually needed a blue button in the first place.

Why Software Teams Should Care

In traditional software development, we tend to collapse these into a single activity called “testing.” We write unit tests, integration tests, and end-to-end tests. If they pass, we ship. But this conflation can lead to a peculiar failure mode: shipping software that passes every test while completely missing the mark.

I’ve seen teams with 95% code coverage, comprehensive CI/CD pipelines, and rigorous code review processes ship features that users ignore entirely. Every verification box was checked. The validation step was skipped or assumed.

The opposite happens too. Teams so focused on user feedback and rapid iteration that they accumulate technical debt, ship buggy code, and eventually can’t move fast enough to respond to the market. All validation, no verification.

Verification in Practice

Verification activities for software typically include:

  • Unit tests confirming individual functions behave as specified
  • Integration tests checking that components work together correctly
  • Static analysis ensuring code follows defined standards
  • Code review verifying implementations match design decisions
  • Performance testing against documented requirements

The key characteristic is that verification has clear, objective criteria. Either the function returns the expected value or it doesn’t. Either the API responds within 200ms or it doesn’t. You can automate most verification.

Validation in Practice

Validation activities look quite different:

  • User testing with actual target users attempting real tasks
  • A/B testing to see if changes improve meaningful metrics
  • Beta programs gathering feedback from early adopters
  • Stakeholder reviews confirming the product meets business needs
  • Field testing in production environments

Validation is inherently messier. Success criteria are often subjective or emergent. You might build exactly what users said they wanted, only to discover they didn’t actually know what they needed. Validation requires judgment, iteration, and sometimes uncomfortable conversations about whether the whole approach is wrong.

The Systems Engineering Perspective

Systems engineers developed this distinction because they work on projects where getting it wrong is catastrophic. When you’re building aircraft, medical devices, or power plants, you can’t just ship and iterate. The V-model and similar frameworks explicitly separate verification and validation activities throughout the development lifecycle.

But even in software, where we have the luxury of continuous deployment, the distinction matters. Verification without validation produces technically excellent products nobody wants. Validation without verification produces products that might solve real problems but are unreliable, insecure, or unmaintainable.

Finding the Balance

The healthiest engineering organizations I’ve worked with treat verification and validation as complementary disciplines, not competing priorities. They have:

  • Clear requirements that can be objectively verified
  • Regular validation touchpoints with real users throughout development
  • Automated verification pipelines that catch regressions quickly
  • Feedback loops that update requirements based on validation findings

When a validation activity reveals that a feature isn’t solving the intended problem, they don’t just hack in fixes. They update the requirements, re-verify against the new spec, and validate again. The cycle continues.

The Bottom Line

Next time you’re reviewing your testing strategy, ask yourself: are we only verifying, or are we also validating? A comprehensive test suite tells you the code works as designed. Only validation can tell you the design was right.

Build the thing right. But first, make sure it’s the right thing.