unity-coding-skills

A Claude Code plugin for Unity development that enables coding agents to work autonomously through a test-first workflow — writing reliable, maintainable tests before production code, then iterating to completion without constant oversight.

Reliable tests give the agent a clear signal: green means done. This plugin provides the methodology, conventions, and tools to make that signal trustworthy.

Included Skills

Skill Description Required
code-writing-guide Coding conventions and guidelines for Unity C# projects
edit-scene Creates and modifies .unity and .prefab files MCP server and MCP Server Extension for Unity plugin
fix-bug Diagnoses and fixes bugs using a test-first workflow (reproduce, diagnose, fix)
plan-feature Orchestrates the test-first planning workflow for feature implementation in plan mode
refine-tests Reviews existing test code for conformance to the test design and writing guides, then plans the refinement
run-tests Running Unity tests via the run_unity_tests tool MCP server and MCP Server Extension for Unity plugin
test-designing-guide Design maintainable test cases; reduce redundant tests, tests without assertions, and unnecessary test doubles
test-writing-guide Conventions for writing Unity Test Framework test code Test Helper and UI Test Helper package
unity-yaml-editing-guide Guidelines for directly hand-editing Unity YAML asset files

Included Subagents

Agent Description
failing-test-writer Implements test code from the plan file's Test Cases table and confirms tests fail as expected (Step 2 of dev workflow)
test-deduplicator Removes duplicate tests and merges parameterizable tests in modified test files (Step 4 of dev workflow)
test-designer Designs test cases during plan mode after class/method designs are produced, using the test-designing-guide skill

Installation

User-scope installation

Add the marketplace and install the plugin:

/plugin marketplace add nowsprinting/unity-coding-skills
/plugin install unity-coding-skills@nowsprinting-unity-coding-skills

Project-scope installation (team sharing)

Add the marketplace and install the plugin with --scope project:

/plugin marketplace add nowsprinting/unity-coding-skills
/plugin install unity-coding-skills@nowsprinting-unity-coding-skills --scope project

Commit the resulting .claude/settings.json to your repository.

[!NOTE]
When team members trust the project folder, Claude Code prompts them to install the marketplace and plugin automatically.

Recommended Project Settings

1. MCP Server Configuration

The run-tests and edit-scene skills require the JetBrains Rider built-in MCP server and extension.

  1. Enable built-in MCP Server
  2. Click the "Auto-Configure" button
  3. Install MCP Server Extension for Unity plugin

[!IMPORTANT]
When Rider is earlier than 2026.2 and you are using other JetBrains IDEs simultaneously with Rider, port numbers are assigned in the order they are launched. For example, if you launch Rider after IDEA, the port number for Rider will be 64343.

[!TIP]
The MCP server is registered under different names depending on your Rider version: rider on Rider 2026.2 or later, jetbrains on versions earlier than 2026.2.

[!TIP]
The JetBrains MCP server also provides tools useful for the coding agents, e.g., search_symbol, find_files_by_glob.

2. Enforcing coding rules via .editorconfig

Any coding rules or Roslyn analyzer diagnostics you want Claude to respect should be set to warning or higher severity in .editorconfig.

For example, to prevent leaving unused code, add the following diagnostics:

resharper_unused_type_local_highlighting = warning
resharper_unused_type_global_highlighting = warning
resharper_unused_member_global_highlighting = warning
resharper_unused_member_local_highlighting = warning

The Rider plugins for measuring complexity are also useful:

Usage

Test-first feature implementation planning

Type in plan mode:

/plan-feature <SPEC>

The created plan file includes the following:

  • Layered-designed test cases
    • Reduce redundant tests, tests without assertions, and unnecessary test doubles
    • Editor tests (Edit Mode tests for editor extensions and validate assets)
    • Unit tests (Play Mode tests for runtime code)
    • Integrated tests including UI operation
    • Visual verification tests using image analysis
  • Test-first development workflow
    • Effective (failable) test code
    • Definition of Done
  • Run static analysis to improve internal quality
  • Run the Claude Code built-in /simplify skill

Bug fixes through reproduction testing

Type out of plan mode:

/fix-bug <INCIDENT>

Create, run, and verify tests to reproduce the bug, then fix it.

[!TIP]
The INCIDENT can specify an issue description or the failed test name.

[!NOTE]
Depending on the incident, the root cause may be identified before writing a reproduction test. Under adjustment.

Refine existing test code for conformance to the test design and writing guides

Type in plan mode:

/refine-tests <PATH>

Contributing

Contributions are welcome. However, we will decline contributions that we cannot maintain — such as adding support for different coding agents or MCP servers. Please fork this repository and customize it for your needs instead.

License

This project is released into the public domain under the Unlicense.