tdd'er

A plugin for pi, Claude Code, and OpenCode that guides AI agents through disciplined Test-Driven Development and Clean Code practices.

Note that currently this is WORK IN PROGRESS! I'm not even trying to keep it stable or tested. At the moment, I'm writing it only for my personal use; it may also work for you, but be ready to have issues; I'd be happy to hear about them!

Features

• TDD discipline: Strict Red-Green-Refactor cycles with baby steps and guessing game
• Clean Code review: Automated code review during refactor phases via subagent
• APP mass calculations: Objective code complexity measurement
• Language-agnostic core: TDD and Clean Code principles work with any language
• Extensible: Add language skills (Java, TypeScript, ...) and build-system skills (Maven, npm, ...)
• Unfolding Architecture: Progressive architectural decisions — start simple, add complexity only when it reduces complexity
• Configurable human-in-the-loop: Control how often the AI pauses for your input

Skills

Language-agnostic core skills work with any language. Language and build-system skills complement them automatically when matching files are detected.

Skill	Purpose
tdd	Core TDD process (Red-Green-Refactor, baby steps, guessing game)
clean-code	Clean Code principles (naming, SOLID, smells, method design)
app	Absolute Priority Premise mass calculations
java	Java-specific conventions (var, BDD testing, static imports)
unfolding-architecture	Progressive architectural decisions (start simple, unfold on demand)
integration-architecture	Integration messaging patterns (commands vs events, push vs pull, reliability)
maven	Maven-specific conventions (test execution, project structure)
nested-fixture-pattern	JUnit nested fixture pattern for layered test preconditions
grill-po	Requirements grilling session with a PO: sharpens terminology, documents features as Gherkin, updates bounded-context files and ADRs inline
project-hygiene	Interaction style, commit conventions, documentation discipline
github-safety	Prompt-injection defense for GitHub issues and pull requests
prove-me-wrong	Devil's advocate mode: finds the strongest objections to the user's position

Extensions

Extensions add active behaviour beyond passive skills — they register commands, tools, and UI components directly into the coding agent.

quarkus (pi only)

Integrates quarkus-agent-mcp into pi so the LLM can manage Quarkus dev-mode applications without leaving the chat.

Auto-activation: the extension detects whether the current directory is a Quarkus project (contains a pom.xml or build.gradle referencing quarkus) and starts the MCP server lazily in the background. All quarkus-agent-mcp tools (quarkus_start, quarkus_stop, quarkus_status, quarkus_skills, quarkus_searchDocs, quarkus_callTool, …) are registered as native pi tools and become available to the LLM automatically.

Footer status: a live status indicator in the pi footer shows the running app state:

• quarkus ● :8080 — running on the detected port
• quarkus ◌ starting… — dev mode booting
• quarkus ⚠ crashed — process exited unexpectedly
• (blank) — stopped / not started

/quarkus command: a unified slash command for common Quarkus actions. With no argument it opens an interactive selector; with an argument it dispatches directly. Tab-completion lists all subcommands.

Subcommand	Behaviour
status	Show the state of all discovered Quarkus services; with an arg, show just that module (direct, LLM on failure)
start	Start a discovered Quarkus service in dev mode; with multiple services it picks, and supports --profiles=dev,foo (LLM on failure)
stop	Stop one or more managed apps; with no args opens a picker, args can be module names (direct, LLM on failure)
logs	Show recent log output (direct, LLM on failure)
list	List all managed Quarkus instances (direct, LLM on failure)
agent-log	Read the MCP server's own log file (direct, LLM on failure)
restart	Hot-reload the app (direct, LLM on failure)
open	Open the app in the browser
devui	Open the Quarkus Dev UI in the browser
info	Show app status, endpoints, and dev services (requires dev mode)
skills	Manage community skills: list installed, delete, browse and install new ones
update	Check for Quarkus updates — output always sent to LLM for analysis
search-tools	Discover Dev MCP tools on the running app — output sent to LLM for analysis
test-affected	Run tests affected by recent changes — results always sent to LLM for analysis
test-all	Run the full test suite — results always sent to LLM for analysis
mcp-restart	Restart the quarkus-agent-mcp server process itself
mcp-tools	List all tools advertised by the MCP server (output sent to LLM)

In multi-module Maven repos, /quarkus status scans all discovered Quarkus services and overlays their runtime state from the managed-instance list, so stopped services are shown too. /quarkus start uses the same discovery and supports an optional positional module/path plus --profiles=dev,foo (no spaces). Other instance-scoped subcommands (stop, logs, restart, open, devui, info, test-affected, test-all) no longer blindly assume the cwd is the target; they prompt when needed and also accept a positional module/path. search-tools keeps its positional query argument, so its target is inferred or picked rather than passed explicitly.

Dispatch strategy: direct subcommands call the MCP tool immediately and show the result as a notification. On failure, the error output is automatically forwarded to the LLM with "what went wrong and how should I fix it?". update, test-affected, and test-all always route through the LLM because their output is analytical rather than a simple pass/fail signal.

maven

Structured Maven execution with test report parsing, compilation error extraction, and Maven Central version lookup.

pi extension: registers maven_run, maven_project_info, and maven_lookup_version tools plus a /maven slash command with live progress widget.

CLI (tdder-maven): the same functionality as a standalone command, usable from any agent that has shell access (Claude Code, OpenCode, Cursor, terminal, …). Requires tsx on your PATH. Run tdder-maven help for usage.

All commands output structured JSON to stdout. Non-zero exit code on failure.

idea (pi only)

Integrates the official JetBrains MCP Server plugin into pi so the LLM can use IntelliJ IDEA's PSI, inspections, refactorings, and debugger without leaving the chat.

Auto-activation: the extension is always loaded but lazy-connects to the IDE's MCP endpoint (default http://127.0.0.1:64342/sse). On every probe it sends a cheap project-scoped call (e.g. get_project_modules) with projectPath = pi's CWD. Three outcomes drive the footer:

• idea ● — IDE reachable and pi's CWD is open as a project
• idea ⚠ not open — IDE reachable, but pi's CWD isn't one of the open projects (tools are hidden; the list of currently open projects is surfaced for diagnosis)
• (blank) — IDE not reachable

projectPath injection: every JetBrains MCP tool takes an optional projectPath. The extension always injects pi's CWD on every forwarded call, overriding whatever the LLM tries to pass. The LLM should never think about projectPath — same way it doesn't think about filesystem roots.

Modes of operation (vocabulary): tools are tagged with a 2×3 lens so the LLM can pick the right family for the task. This vocabulary is documented per-tool in the extension's tool descriptions; it may later be promoted to a dedicated idea skill if cross-tool patterns emerge.

	code (static)	runtime (dynamic)	session (IDE / env)
explore	search symbols, get inspections, project model	debugger inspect, app logs / metrics / traces	which files are open, IDE version
modify	edit, rename, reformat	set breakpoint, set variable, run, hot-reload	open file in editor, switch project

• code (static) = facts about source / config / dependencies (true regardless of any process running)
• runtime (dynamic) = facts about the program being developed when it's executing
• session (env) = facts about the development environment itself; mostly serves LLM↔human collaboration

Available tools — tagged with the 2×3 modes vocabulary above (31 total):

Modes	Tools
explore/code	search_symbol, get_symbol_info, search_in_files_by_regex, find_files_by_glob, list_directory_tree, get_project_modules, read_file, get_file_problems, get_project_dependencies, get_file_text_by_path, get_repositories
explore/session	get_all_open_file_paths
modify/session	open_file_in_editor
modify/code	rename_refactoring, reformat_file
modify/runtime	build_project, get_run_configurations, execute_run_configuration
explore/runtime + modify/runtime	xdebug_get_stack, xdebug_get_frame_values, xdebug_get_threads, xdebug_evaluate_expression, xdebug_get_value_by_path, xdebug_get_debugger_status, xdebug_list_breakpoints, xdebug_set_breakpoint, xdebug_remove_breakpoint, xdebug_set_variable, xdebug_run_to_line, xdebug_control_session, xdebug_start_debugger_session

Explicitly out of scope (duplicates of pi built-ins):

• replace_text_in_file, create_new_file — use pi's edit / write
• find_files_by_name_keyword — use find_files_by_glob
• search_file, search_text, search_regex, search_in_files_by_text — use search_in_files_by_regex
• execute_terminal_command — redundant with pi's bash

Agents

Agent	Purpose
clean-code-reviewer	Autonomous code review during refactor phases

Hooks (Claude Code only)

The Claude Code plugin includes a PreToolUse hook that reminds the agent to load language/build-system skills before editing matching files:

File pattern	Skill reminded
*.java	java
pom.xml	maven

Configuration

Human-in-the-Loop

If no settings file exists, the TDD skill will ask on first use and persist your choice. You can also create .claude/tdder.local.md manually in your project root:

---
hitl: every-phase
---

Level	Behavior
every-phase	Stop after every Red, Green, Refactor phase
end-of-cycle	Stop after each complete Red-Green-Refactor cycle
off	Run autonomously, report at end

Installation

pi

Install the tdder package, which registers all skills and extensions automatically:

pi install git:github.com/t1/tdder

The quarkus extension activates automatically in Quarkus projects (requires jbang on your PATH).

The idea extension activates when the IntelliJ IDEA MCP Server plugin is reachable on 127.0.0.1:64342 and the current pi working directory matches an open IDE project.

Claude Code

Add this repo as a marketplace, then install the plugin:

/plugin marketplace add t1/tdder
/plugin install tdder@t1

Note that the official docs are not very clear about this, but you actually need a marketplace.json, even if you have only a single plugin.

OpenCode

Add tdder to the plugin array in your opencode.json (global or project-level):

{
  "plugin": ["tdder@git+https://github.com/t1/tdder.git"]
}

Restart OpenCode. The plugin auto-installs and registers all skills.

Development

Development currently requires tsx to be installed and available on your PATH, because repo utility scripts use a #!/usr/bin/env tsx shebang.

For example:

npm install -g tsx

Separately released pi extension packages in this repo vendor shared TypeScript from elsewhere in this repo during a sync step instead of publishing a separate shared package. In this setup, pretest and prepack are only safety nets: after every edit to shared code or to a consumer of that shared code, run npm run sync-extensions immediately so development, tests, and packaging all see the same files.

Updating

Claude Code

As of Claude Code v2.1.44, it's not an easy task to update the plugin; even uninstalling and reinstalling doesn't help. The problem is that the marketplace is checked out to ~/.claude/plugins/marketplaces/t1/, while the plugins are cached in ~/.claude/plugins/cache/t1/tdder/. So to update to a new version of the plugin, you'll have to do this:

cd ~/.claude/plugins/marketplaces/t1/ && git pull && rm -r ~/.claude/plugins/cache/t1/tdder/ && cd -

OpenCode

tdder updates automatically when you restart OpenCode.

Extending

To add a new language or build system, create skills/<name>/SKILL.md with the relevant conventions (testing framework, naming, commands, etc.). The skill triggers automatically when working in projects with matching files.