Agent skill
dotnet-writing-plans
Use when you have a spec or requirements for a multi-step .NET backend task, before touching code. Creates concise implementation plans that reference architecture contracts.
Install this agent skill to your Project
npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/other/other/dotnet-writing-plans
SKILL.md
⚠️ Spelling: It's
saurun:(with U), not "sauron"
.NET Writing Plans
Overview
Plans are architectural blueprints, not copy-paste code. Each task references contracts defined in the architecture doc. Implementers use TDD skills to fill in the actual code.
Announce at start: "I'm using the dotnet-writing-plans skill to create the implementation plan."
Save plans to: _docs/plans/YYYY-MM-DD-<feature-name>.md
When NOT to Use
- Single-file bug fix with obvious cause and fix
- Config/environment changes (appsettings, launchSettings, .csproj tweaks)
- Renaming or moving files without logic changes
- Adding a NuGet package with no code changes beyond the import
Plan Document Header
Every plan MUST start with this header:
# [Feature Name] Implementation Plan
> **For Claude:** **REQUIRED SUB-SKILL:** Use `saurun:dotnet-tdd` to implement this plan task-by-task with TDD.
**Goal:** [One sentence describing what this builds]
**Architecture:** `_docs/specs/{DATE}-{feature}-architecture.md`
**Tech Stack:** .NET 9, ASP.NET Core, EF Core 9, SQLite, xUnit, NSubstitute
---
Task Structure
### Task N: [Name]
**Implements:** [Contract reference from Architecture doc, e.g., "POST /lists/{id}/items (Architecture §API Contract)"]
**Files:**
- Create: `exact/path/to/File.cs`
- Test: `tests/exact/path/to/FileTests.cs`
**Behaviors:**
- [Happy path behavior]
- [Error case 1]
- [Error case 2]
**Dependencies:** Task X (if applicable)
Backend Task Examples
Domain Entity Task
### Task 2: ShoppingList aggregate
**Implements:** ShoppingList entity (Architecture §Entity Model)
**Files:**
- Create: `Domain/Aggregates/ShoppingList.cs`
- Test: `Tests/Domain/ShoppingListTests.cs`
**Behaviors:**
- Creating with valid name initializes empty items collection
- Adding item with valid name increases item count
- Adding item when at max capacity throws DomainException
- Removing non-existent item throws DomainException
API Endpoint Task
### Task 5: AddItem endpoint
**Implements:** POST /lists/{id}/items (Architecture §API Contract)
**Files:**
- Create: `Api/Endpoints/ShoppingListEndpoints.cs`
- Test: `Tests/Api/ShoppingListEndpointsTests.cs`
**Behaviors:**
- Valid input → 201 with ShoppingItemDto
- Validates per Architecture §API Contract
**Dependencies:** Task 2 (ShoppingList entity), Task 4 (DbContext)
Note: 401/404 for auth/invalid-id are omitted — standard patterns assumed. Validation rules reference architecture, not repeated.
Infrastructure Task
### Task 4: EF Core DbContext and migrations
**Implements:** Data persistence (Architecture §Infrastructure Decisions)
**Files:**
- Create: `Infrastructure/AppDbContext.cs`
- Create: `Infrastructure/Configurations/ShoppingListConfiguration.cs`
- Modify: `Program.cs` (add DbContext registration)
**Behaviors:**
- DbContext configured with SQLite provider
- ShoppingList entity mapped with owned Items collection
- Migration creates tables matching entity model
**Dependencies:** Task 2 (ShoppingList entity)
What Plans Include
| Element | Required |
|---|---|
| Exact file paths (Create/Modify/Test) | ✓ |
Contract reference (Implements:) |
✓ |
| Behaviors (one line each) | ✓ |
| Task dependencies | When applicable |
What Plans Do NOT Include
| Element | Reason |
|---|---|
| Full test code | TDD skill generates tests from behaviors |
| Full implementation code | Implementer writes from contract + behaviors |
| Step-by-step TDD instructions | TDD skill handles workflow |
| Expected failure messages | TDD skill handles verification |
| "What bugs does this catch?" table | Behaviors implicitly define bug coverage |
| Validation rules | Architecture §API Contract defines these — just reference it |
| DTO field lists | Architecture §API Contract defines these — just reference it |
Standard auth behaviors (401 for unauthed) |
Universal pattern — assumed for all [Authorize] endpoints |
Standard 404 for invalid ID |
Universal pattern — assumed for all {id} routes |
| Mapper descriptions like "maps X to Y" | Obvious from naming convention |
Token budget: Plans for autonomous agents, not humans. Every repeated pattern wastes tokens. If architecture defines it, reference it — don't repeat it.
Test Infrastructure Task
Task 1 of every plan MUST set up test infrastructure:
### Task 1: Test infrastructure setup
**Implements:** Shared test helpers (N/A - infrastructure)
**Files:**
- Create: `Tests/CustomWebApplicationFactory.cs`
- Create: `Tests/TestHelpers.cs`
**Behaviors:**
- CustomWebApplicationFactory configured with SQLite in-memory
- TestHelpers provides authenticated HttpClient creation
- IClassFixture pattern ready for integration tests
Common Mistakes
| Mistake | Fix |
|---|---|
| Writing full test/implementation code | Just list behaviors — TDD skill writes code |
Forgetting Implements: reference |
Every task MUST reference architecture contract |
| Vague behaviors like "handles errors" | Be specific: "Empty name → returns 400" |
| Missing file paths | Every task MUST list exact Create/Modify/Test paths |
| Tasks too large (>3 files) | Split into smaller tasks |
| No test infrastructure in Task 1 | CustomWebApplicationFactory + helpers MUST be Task 1 |
| Repeating validation rules from architecture | Just write Validates per Architecture §API Contract |
| Listing DTO fields | Reference architecture — AuthResponse per Architecture §DTOs |
| Writing "when not authenticated → 401" for every endpoint | Omit — assumed for [Authorize] endpoints |
| Writing "invalid id → 404" for every endpoint | Omit — assumed for {id} routes |
| Describing what mappers do | CategoryMapper obviously maps Category → omit |
Completion
After saving the plan, report:
"Plan saved to _docs/plans/<filename>.md. Ready for execution."
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