Implement Feature

Implement Feature Skill

Use this skill to implement a new feature end-to-end with complete validation from code changes through interactive E2E testing.

What This Skill Does

This is an orchestrator skill that sequences the following steps:

1. Analyze Requirements - Understand the feature request and identify affected components
2. Implement Changes - Generate code changes across backend/frontend as needed
3. Build Backend - Compile .NET backend projects
4. Build Frontend - Compile TypeScript/React frontend
5. Run Tests - Execute unit and integration tests to validate logic
6. Start Aspire Runtime - Spin up the complete application environment
7. Validate E2E - Execute feature-specific happy-path validation in running UI
8. Report Results - Document validation outcomes (success/failure)

This orchestrator halts at the first failure and reports details to the user for remediation.

When to Use

Use this skill when:

• Implementing a new feature from requirements to completion
• Need end-to-end validation that feature works correctly
• Want a guided, checkpoint-based development workflow
• Need to track progress through multiple validation stages

How the Agent Should Use This Skill

Phase 1: Requirements Analysis

Input: Feature requirement or story from the user

Agent Task:

1. Analyze the feature request to understand:

   • What user-facing behavior is expected?
   • What components need changes (Frontend, API, Application logic)?
   • What data/models are involved?
   • What happy-path user journey should be validated?

2. Document your understanding:

   • Affected backend services (Api, Application, Worker)
   • Frontend components to modify (React components, pages)
   • Database changes needed (new entities, migrations)
   • API endpoints to create or modify
   • Happy-path validation flow (e.g., "user clicks button → form displays → data saved → list updated")

3. Checkpoint: Confirm understanding with user before proceeding to implementation

Example Analysis:

Feature: Change survey creation button to purple
Analysis:
- Frontend Component: `src/client/ui/src/components/SurveyList.tsx` (button styling)
- Backend Changes: None required
- Happy-Path: Navigate to survey list → verify button is purple

Phase 2: Implementation

Agent Task:

1. Implement backend changes (if any):

   • Create/modify API endpoints in src/server/FakeSurveyGenerator.Api/
   • Create/modify business logic in src/server/FakeSurveyGenerator.Application/
   • Create/modify domain models as needed
   • Add/update database migrations if schema changes

2. Implement frontend changes (if any):

   • Modify React components in src/client/ui/src/
   • Update types/interfaces for new API contracts
   • Update UI styling/layout as needed
   • Handle new validation/error scenarios

3. Add/Update Tests:

   • Unit tests in src/server/FakeSurveyGenerator.Application.Tests/
   • Integration tests in src/server/FakeSurveyGenerator.Api.Tests.Integration/
   • Aim for coverage of happy-path and edge cases

4. Checkpoint: Review changes are complete before proceeding to validation

Implementation Checklist:

• Backend logic implemented (if needed)
• Frontend UI updated (if needed)
• Tests written for new logic
• No syntax errors in code
• Dependencies updated if needed (NuGet, npm)

Phase 3: Build Validation

Agent Task: Invoke Build Backend Skill

Invoke: build-backend skill
Expected: Exit code 0, no compilation errors
On Failure: Report compilation errors to user, stop

Agent Task: Invoke Build Frontend Skill

Invoke: build-frontend skill
Expected: Exit code 0, no TypeScript errors
On Failure: Report build errors to user, stop

Phase 4: Test Validation

Agent Task: Invoke Test Backend Units Skill

Invoke: test-backend-units skill
Expected: All tests pass, exit code 0
On Failure: Report failed test names and assertions, stop

Checkpoint: All tests must pass before proceeding to E2E

Phase 5: Runtime Validation

Agent Task: Invoke Validate Aspire Runtime Skill

Invoke: validate-aspire-runtime skill
Expected: All resources healthy, UI endpoint discovered
Steps:
1. Run `aspire run` command in a terminal
2. Use Aspire MCP list_resources tool to monitor health
3. Wait for all resources (sql, cache, api, worker, ui) to be healthy
4. Extract UI endpoint URL (typically https://localhost:3000)
5. Report endpoint to next skill

On Failure: Report which resource failed to start, stop

Important: Leave Aspire running after this step; it's needed for E2E validation

Phase 6: E2E Validation

Agent Task: Invoke Validate E2E Skill

Invoke: validate-e2e skill
Context Provided to E2E Skill:
- UI endpoint URL from Aspire runtime
- Feature requirements/happy-path flow from Phase 1

E2E Skill Execution:
1. Use Playwright MCP to navigate UI
2. Execute feature-specific validation steps
3. Verify expected state changes and behavior
4. Report pass/fail with evidence

Expected: All validations pass
On Failure: Report specific validation failures, stop

Phase 7: Results & Cleanup

Success Path ✅:

1. Report to user: "Feature implementation validated successfully!"
2. Provide summary:
   • Builds: Passed ✅
   • Tests: N tests passed ✅
   • E2E Validation: Feature working as expected ✅
3. User can stop Aspire (Ctrl+C) when ready

Failure Path ❌:

1. Report to user: "Validation failed at [specific stage]"
2. Provide details:
   • Stage: [Build/Test/Runtime/E2E]
   • Error: [specific error details]
   • Recommendation: [fix guidance if applicable]
3. User must fix issues and re-run validation from failing stage

Checkpoint & Halt Strategy

The orchestrator uses the following halt behavior:

Typical Feature Implementation Timeline

1. Analysis - 5-10 minutes
2. Implementation - 15-60 minutes (depends on feature complexity)
3. Builds - 1-2 minutes
4. Tests - 1-3 minutes
5. Aspire Startup - 2-5 minutes (first run slower)
6. E2E Validation - 2-10 minutes
7. Total - 30-90 minutes end-to-end

Common Feature Types & Implementation Patterns

Type: New API Endpoint

• Backend Changes: Create DTO, handler, controller action
• Frontend Changes: Create API client call, UI components
• Tests: Unit test handler logic, integration test endpoint

Type: Frontend UI Component Change

• Backend Changes: Usually none
• Frontend Changes: Modify React component, styles
• Tests: Snapshot tests, interaction tests in acceptance tests

Type: Database Feature (e.g., new entity)

• Backend Changes: Create entity, update DbContext, add migration
• Frontend Changes: Add UI for new entity (if user-facing)
• Tests: Repository/handler tests with real database (Testcontainers)

Type: Cross-Cutting (spans frontend + backend + database)

• All layers: Implement complete flow end-to-end
• Tests: Full integration test from API to database
• E2E: Happy-path user journey through complete workflow

Reference: Available Skills

Each phase invokes a specific skill:

For more details on each skill, see their individual SKILL.md files.

Foundation Knowledge

Reference: fake-survey-gen-foundation skill for detailed project architecture, service topology, and patterns.

Example: Complete Feature Implementation

Scenario: "Add ability to search surveys by title"

Phase 1: Analysis

Feature: Search surveys by title
Changes Needed:
- Backend: Add search parameter to GetSurveys API endpoint
- Frontend: Add search input box to survey list page
- Happy-Path: List surveys → type search term → verify filtered results

Phase 2-4: Implement & Build

- Add `searchTerm` parameter to Application service method
- Add filtering logic (e.g., LINQ .Where(s => s.Title.Contains(searchTerm)))
- Add React input field with onChange handler
- Call API with search parameter
- Write unit tests for search logic
- Write integration test for endpoint with search
- Builds pass ✅
- Tests pass ✅

Phase 5: Runtime

- Start aspire run
- Resources reach healthy ✅
- UI endpoint: https://localhost:3000

Phase 6: E2E Validation

- Navigate to https://localhost:3000
- See survey list with multiple surveys
- Type "test" in search box
- Verify only surveys with "test" in title remain
- Clear search, verify full list returns
- Validation passes ✅

Result: Feature implemented, tested, and validated end-to-end ✅

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