A Simple Checklist for Writing Requirements That Engineers Can Actually Use

Source: Dev.to

Most requirement docs fail for one simple reason

They are hard to execute. Not because they are incomplete or lack detail, but because they are unclear. This post is a practical checklist to fix that—no theory, no fluff, just a usable structure.

What counts as a functional requirement (quick reset)

Functional requirement = what the system does when a user does something.

If a line does not describe:

• a user action
• a system response

…it’s not a functional requirement.

Step 1: Identify functional requirements (fast method)

Use this 3‑question loop:

1. Who is using the system?
2. What are they doing?
3. What should the system do back?

Example

User: logs in
Action: enters email + password
System: validates → allows access OR shows error

That becomes one requirement. Repeat the loop until all key flows are covered.

Quick checklist

• Every user action is listed
• Every action has a system response
• No missing flows (login, reset, checkout, etc.)

Step 2: Write requirements in a standard format

Avoid long paragraphs. Use a simple structure:

WHEN [user action]
THEN [system response]

Examples

WHEN user submits login form
THEN system validates credentials and grants access if correct

WHEN user clicks reset password
THEN system sends reset link to registered email

Why this works

• Easy to read
• Easy to test
• No ambiguity

Step 3: Validate each requirement (engineer check)

Clarity check

• Can two people read this and understand the same thing?

Testability check

• Can this be verified with a simple test case?

Scope check

• Does this describe only one action and one result?

If any answer is no, rewrite the requirement.

Functional vs non‑functional requirements (quick table)

Rule

• If it describes behavior → functional
• If it describes quality → non‑functional

Keep them separate.

Common mistakes (and fixes)

1. Writing vague requirements

Bad

System should handle login properly

Fix

WHEN user enters valid credentials
THEN system grants access to dashboard

2. Combining multiple actions

Bad

System validates login and sends welcome email and logs activity

Fix
Split into three separate requirements.

3. Missing edge responses

What happens on wrong password?
What happens on empty input?

Fix
Add explicit failure cases.

Mini template you can reuse

Feature: [Feature Name]

Requirement 1:
WHEN [user action]
THEN [system response]

Requirement 2:
WHEN [user action]
THEN [system response]

Failure case:
WHEN [invalid action]
THEN [system response]

How this improves testing

Every requirement becomes a test.

Requirement

WHEN user enters correct password
THEN system grants access

Test

• Input: valid credentials
• Expected: access granted

Clear input, clear output—no confusion.

Final checklist before handoff

• All user flows are covered
• Each requirement = one action + one result
• Requirements use consistent format
• No mixed functional and non‑functional items
• Every requirement can be tested

If this passes, the doc is usable.

Bottom line

Functional requirements are not about writing more; they’re about writing clearly.

• Identify actions
• Define responses
• Keep everything testable

Full guide + resources