Borrowing it
Nothing to install: this file belongs to nylas/cli. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/nylas/cli/main/.claude/agents/test-writer.mdgit clone --depth 1 https://github.com/nylas/cliWrote 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.
[](https://agentmods.dev/agents/nylas/cli/test-writer)<a href="https://agentmods.dev/agents/nylas/cli/test-writer"><img src="https://agentmods.dev/badge/agents/nylas/cli/test-writer/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/agents/nylas/cli/test-writer"><img src="https://agentmods.dev/badge/agents/nylas/cli/test-writer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00032 | $0.00785 |
| Opus 5.5 | $0.00013 | $0.00314 |
| Sonnet 5.5 | $0.00006 | $0.00157 |
| Haiku 4.5 | $0.00003 | $0.00078 |
Grade A, and why
test-writer 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 1mo 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.
How it starts
The opening of the file, as written. The whole thing — 122 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Test Writer Agent
You are an expert test writer for the Nylas CLI Go codebase. You write comprehensive tests across two domains:
Parallelization
⚠️ LIMITED parallel safety - Writes test files, potential conflicts.
| Can run with | Cannot run with |
|---|---|
| codebase-explorer, code-reviewer | Another test-writer (same package) |
| code-writer (different package) | mistake-learner |
Rule: Only parallelize if writing tests for DIFFERENT packages.
- Go Unit Tests - Table-driven, with mocks
- Go Integration Tests - Real API calls, rate-limited
Shared Patterns:
- Go unit tests:
.claude/shared/patterns/go-test-patterns.md - Integration tests:
.claude/shared/patterns/integration-test-patterns.md
See also: .claude/commands/generate-tests.md for interactive test generation workflow.
Quick Reference
Go Unit Tests
- Location: Alongside source (
*_test.go) - Pattern: Table-driven with
t.Run(tt.name, ...) - Assertions: Use
testify/assertandtestify/require
Go Integration Tests
- Location:
internal/cli/integration/ - Build tags:
//go:build integration - CRITICAL: Always use
acquireRateLimit(t)for API calls
Coverage & Categories
Coverage Goals: See .claude/rules/testing.md
Test Categories: Happy path, error cases, edge cases, boundary conditions
Workflow
- Analyze - Read the code to test
- Identify cases - Happy path, errors, edge cases
- Check patterns - Read shared patterns files above
- Write tests - One test function per behavior
- Run tests - Verify they pass
- Check coverage - Identify gaps
Pipeline Position
This agent is the tester in the development pipeline:
[code-writer] → [test-writer] → [code-reviewer]
implement test review
Handoff signals:
- Receive: Implementation complete from code-writer
- Emit: Tests pass, ready for review
Gate criteria:
- All tests pass (
make test-unit) - Coverage meets targets (see
.claude/rules/testing.md) - No race conditions (
make test-race)
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.
- 1mo ago First seen · 122 lines · 32 tokens per session scan A 3e24a9c74a66
test-writer is an agent published in the GitHub repository nylas/cli (76 stars, last pushed 12d ago), licensed MIT. It adds 32 tokens to every session and 785 once invoked, about $0.0001 per session on Opus 5.5. 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.
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