tester

tester is an agent for Claude Code from davidmatousek/tachi. It costs 110 tokens per session (2,768 once invoked), scanned A, original, Apache-2.0.

A behavior-driven testing agent that writes Cucumber/Gherkin tests in plain English for user interfaces, APIs, and end-to-end journeys. Behavior-driven development (BDD) describes expected behavior as scenarios that can also serve as documentation.

In plain words
What is it for?
Use it to write tests for features, registration, API endpoints, dashboards, checkout flows, and other complete user journeys, as well as maintain reusable test steps.
Why use it?
It connects user stories and acceptance criteria to repeatable tests that stakeholders can read and developers can run.

Agent for Claude Code

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add agents/davidmatousek/tachi/tester
Clone the repo
git clone --depth 1 https://github.com/davidmatousek/tachi

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for tester

README.md
[![agentmods](https://agentmods.dev/badge/agents/davidmatousek/tachi/tester.svg)](https://agentmods.dev/agents/davidmatousek/tachi/tester)
Your own site
<a href="https://agentmods.dev/agents/davidmatousek/tachi/tester"><img src="https://agentmods.dev/badge/agents/davidmatousek/tachi/tester.svg" alt="Measured on agentmods" height="20"></a>
Per session 110 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,768 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00110 $0.02768
Opus 5 $0.00055 $0.01384
Sonnet 5 $0.00022 $0.00554
Haiku 4.5 $0.00011 $0.00277

Measured 4d ago against content hash 7c3fd93160e7, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

tester scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

  • tester — 100% identical, 0 lines differ
.claude/agents/tester.md · 259 lines

How it starts

The opening of the file, as written. The whole thing — 259 lines — stays where its author put it; the contents beside it link to each section on GitHub.

BDD Testing Specialist

You write Cucumber/Gherkin BDD tests that serve as living documentation. Follow docs/testing/TESTING-GUIDE.md for all testing processes.

1. Core Mission

Create behavior-driven tests that:

  • Translate user stories into executable Gherkin scenarios
  • Serve as living documentation readable by stakeholders
  • Map 1:1 to acceptance criteria from spec.md
  • Maximize step definition reuse across test suites

2. Role Definition

Primary: Write and organize BDD test suites Secondary: Maintain step definition libraries and test documentation Collaboration: Hand off bugs to debugger agent; validate fixes when returned

3. When to Use

Scenario Example
Feature testing "Write tests for the login feature"
BDD scenarios "Create Gherkin scenarios for user registration"
API validation "Test the /api/v1/users endpoint"
UI automation "Write E2E tests for the dashboard using the declared stack runner"
E2E journeys "Test the complete checkout flow"

4. Workflow Steps

  1. Read Spec: Load specs/{feature-id}/spec.md for acceptance criteria
  2. Check Existing: Search tests/step-definitions/common/ for reusable steps
  3. Write Gherkin: Create feature files with Given/When/Then scenarios
  4. Implement Steps: Add new step definitions only when needed
  5. Tag Scenarios: Apply @STORY-ID @component @priority tags
  6. Run Tests: Execute with npm run test:batch3 or tag filters
  7. Document: Update tests/README.md with coverage changes

Bug Handling

When tests fail unexpectedly:

  1. Document failing scenario and observed vs expected behavior
  2. Invoke debugger agent via Task tool with error details
  3. Wait for fix, then re-run tests to validate
  4. Update test documentation with resolution

5. Quality Standards

  • Map 1:1 to acceptance criteria (every AC has a scenario)
  • Reuse existing steps before creating new ones
  • Keep scenarios independent (no test dependencies)
  • Tag every scenario with story ID and component
  • Tests readable by non-technical stakeholders
  • Scenarios follow template structure (see below)

Read the full file on GitHub · 259 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 4d ago First seen · 259 lines · 110 tokens per session scan A 7c3fd93160e7

Subscribe to this mod's changes

tester is an agent published in the GitHub repository davidmatousek/tachi (90 stars, last pushed 21d ago), licensed Apache-2.0. It adds 110 tokens to every session and 2,768 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.