tailtest — Claude Code plugin: tests after every edit
A hook-driven plugin that queues each file Claude writes, builds scenarios for it and runs them through your own test runner. Failures come back in the same turn.
/plugin marketplace add anthropics/claude-plugins-community
/plugin install tailtest@claude-communityWhat tailtest does
tailtest sits inside the build loop. When Claude writes a file, the plugin picks it up and generates scenarios through its R1-R15 rule layer. Those scenarios describe business behaviour rather than function signatures, then go to whatever runner the project already uses: pytest, vitest, jest, go test and others.
The runner is detected from standard manifests such as pyproject.toml, package.json, go.mod, build.gradle.kts, *.csproj and *.sln. Supported languages are Python, TypeScript, JavaScript, Go, Ruby, PHP, Java, Kotlin, C#, Rust. A clean run prints a single pass line; a failure prints one line and asks whether to fix it.
Depth lives in .tailtest/config.json at the project root. simple produces 2-3 scenarios, standard produces 5-8 and is the default, thorough produces 10-15. Adversarial mode R15 pushes generation toward eight categories of breakage; the author used it to find 16 real bugs across 47 open-source Python repositories. MIT licensed, no telemetry, no SaaS account. Restart Claude after installing.
What it helps with
- run tests right after the agent rewrites a file
- catch a regression while the edit is still in context
- get scenarios about business behaviour instead of signatures
- wire automatic testing into an existing runner without rewriting configs
- hunt edge-case breakage with adversarial mode R15
Example prompts for the agent
- Check that tailtest picked up my
pyproject.tomland run scenarios for the last edit - Set depth to
thoroughin.tailtest/config.jsonand re-run the check - Turn on R15 and show which breakage categories it found in this module
How to install tailtest
Plugin marketplace
/plugin marketplace add anthropics/claude-plugins-community/plugin install tailtest@claude-communityStep by step, with commands for each platform: Claude Code plugins: marketplaces, installing, and building your own
Questions about tailtest
How do I install tailtest in Claude Code?
Add the marketplace with /plugin marketplace add anthropics/claude-plugins-community, then install the plugin: /plugin install tailtest@claude-community. Restart Claude afterwards.
What does tailtest do?
It watches files written by Claude, generates scenarios through the R1-R15 rule layer and runs them with your test runner. Results are handed back to the agent within the same turn.
Which languages and runners are supported?
Python, TypeScript, JavaScript, Go, Ruby, PHP, Java, Kotlin, C#, Rust. The runner is detected from standard project manifests, so you do not configure it by hand.
Source text
SKILL.md · MIT
# tailtest -- AI software testing for Claude Code
[](https://opensource.org/licenses/MIT)
[](https://github.com/avansaber/tailtest)
[](https://github.com/avansaber/tailtest/releases/latest)
[](https://tailtest.com/platform/agent-edits/)
> You build. Claude builds. tailtest makes sure it works.
**tailtest** is the open-source AI software testing layer for [Claude Code](https://www.anthropic.com/claude-code). It runs inside the build loop: every time Claude edits a file, tailtest queues the file, generates production-shaped scenarios using the R1-R15 rule layer, runs them with your existing test runner (pytest, jest, go test, etc.), and surfaces failures back to Claude within the same turn. Hook-based. Deterministic. No prompting required.
Open source (MIT), no telemetry, no SaaS account. Includes adversarial mode (R15) that biases scenario generation toward 8 breakage categories -- the mode we've used to find 16 real bugs across 47 open-source Python repositories.
**[Read more on tailtest.com](https://www.tailtest.com/) · [Platform overview](https://www.tailtest.com/platform/) · [Agent-edit testing deep dive](https://www.tailtest.com/platform/agent-edits/) · [Full docs](https://www.tailtest.com/docs/)**
---
## Install
```bash
claude plugin marketplace add avansaber/tailtest
claude plugin install tailtest@avansaber-tailtest
```
Restart Claude Code after install. No other setup required.
## Update
```bash
claude plugin marketplace update avansaber-tailtest
claude plugin update tailtest@avansaber-tailtest
```
## Uninstall
```bash
claude plugin remove tailtest@avansaber-tailtest
```
---
## How it works
After any Claude-written file lands in your project:
1. tailtest generates scenarios that describe real business behavior -- not function signatures
2. It runs them using your existing test runner (pytest, vitest, jest, go test, and more)
3. Pass: `tailtest: N scenarios -- all passed.` Fail: one line surfaced, "want me to fix this?"
---
## Supported languages
Python, TypeScript, JavaScript, Go, Ruby, PHP, Java, Kotlin, C#, Rust
Runners are auto-detected from `pyproject.toml`, `package.json`, `go.mod`, `build.gradle.kts`, `*.csproj`, `*.sln`, and other standard manifests.
---
## Quick config
Create `.tailtest/config.json` in your project root to control depth:
```json
{ "depth": "standard" }
```
Options: `simple` (2-3 scenarios), `standard` (5-8, default), `thorough` (10-15).
See [tailtest.com/docs/config](https://tailtest.com/docs/config) for all options.
---
## Other tailtest variants
Same R1-R15 rule layer, same adversarial test mode, different host integration. **This repo is the Claude Code variant.**
- **[tailtest](https://github.com/avansaber/tailtest)** -- Claude Code plugin (hook-driven; this repo)
- **[tailtest-cursor](https://github.com/avansaber/tailtest-cursor)** -- Cursor plugin (hook-driven)
- **[tailtest-codex](https://github.com/avansaber/tailtest-codex)** -- Codex CLI plugin (hook-driven)
- **[tailtest-cline](https://github.com/avansaber/tailtest-cline)** -- Cline plugin (MCP-driven; reaches 8+ editors via Cline's host coverage)
See [tailtest.com/demo/claude-code](https://tailtest.com/demo/claude-code) for a live walkthrough of this variant, or [tailtest.com/comparison](https://tailtest.com/comparison) for a feature matrix across all four.
---
## License
MIT
© avansaber · MIT · avansaber/tailtest
