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What is Iterative Development?

Iterative development is an approach where you build software in small, incremental cycles. Each cycle produces a working piece of software that you can test and refine. Nelson is built for this workflow, especially with the Nelson Loop feature.

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Manual Iteration

Even without Nelson Loop, you can iterate naturally: 
You: Create a basic Express server

Nelson: [Creates server.js with basic setup]

You: Now add a /users endpoint that returns a list

Nelson: [Adds /users endpoint]

You: Add authentication middleware

Nelson: [Adds auth middleware]

You: The auth middleware has a bug - it's not checking token expiration

Nelson: [Fixes the bug]
Each request builds on the previous work.

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Automated Iteration with Nelson Loop

For more complex tasks, Nelson Loop automates the iteration: 
/nelson-loop "Implement a pagination system for the /users endpoint.
Requirements:
- Accept page and limit query params
- Return total count in response
- Handle edge cases (negative page, etc.)
- Add tests

Output <haha>PAGINATION DONE</haha> when tests pass." --completion-haha "PAGINATION DONE" --max-iterations 15
Nelson will:
  1. Implement pagination
  2. Run tests
  3. See failures
  4. Fix issues
  5. Repeat until tests pass
  6. Output completion signal

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The TDD Cycle

Nelson excels at Test-Driven Development: 
/nelson-loop "Using TDD, implement a password strength validator:

1. Write failing tests for weak passwords (too short, no numbers, etc.)
2. Implement the validator to pass tests
3. Write failing tests for strong passwords
4. Update validator to pass all tests
5. Refactor if needed

Output <haha>TDD COMPLETE</haha> when all tests pass." --completion-haha "TDD COMPLETE" --max-iterations 20

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Debugging Iteration

When debugging, Nelson naturally iterates: 
You: The API is returning 500 errors on the /orders endpoint

Nelson: Let me investigate...

[Reads code, finds potential issue]
[Makes a fix]
[Runs tests - still failing]
[Reads error logs]
[Identifies root cause]
[Applies correct fix]
[Tests pass]

HA-HA! Fixed it. The issue was a null reference when the order had no items.

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Iteration Strategies

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1. Start Simple, Add Complexity

You: Create a basic todo list
You: Now add categories to todos
You: Add due dates
You: Add priority levels
You: Add filtering by category/priority/date

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2. Build the Happy Path First

You: Implement user registration (assume all inputs are valid)
You: Now add validation for email format
You: Add password strength requirements
You: Handle duplicate email gracefully

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3. Write Tests Along the Way

You: Add a search feature to the API
You: Write tests for the search feature
You: The tests are failing - can you fix the implementation?

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Best Practices for Iteration

Keep Iterations Small

Smaller changes are easier to verify and debug

Test After Each Change

Run tests frequently to catch issues early

Let Nelson See Previous Work

Nelson reads files to understand context - use this to your advantage

Set Clear Goals

Each iteration should have a specific, measurable goal

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Example: Iterating on a Feature

Watch how iteration refines a feature: Iteration 1: Basic implementation 
You: Add a /search endpoint that searches todos by title
Iteration 2: Improve search 
You: Make the search case-insensitive
Iteration 3: Add features 
You: Allow searching by description too
Iteration 4: Optimize 
You: Add pagination to search results
Iteration 5: Polish 
You: Add highlighting of matched terms in results
Each iteration builds on the last, resulting in a polished feature.