test-writer

An assistant that writes unit, integration, and end-to-end tests. Unit tests check small pieces of code, integration tests check parts working together, and end-to-end tests check complete user flows.

In plain words
What is it for?
Use it when adding test coverage or writing new tests, then run the project’s test command to verify them.
Why use it?
It helps create tests that verify real requirements, including normal, edge, and error cases, instead of merely matching sample inputs.

Agent

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/alleneubank/claude-code/test-writer
Clone the repo
git clone --depth 1 https://github.com/alleneubank/claude-code
Per session 31 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 466 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 $0.00031 $0.00466
Opus 5 $0.00015 $0.00233
Sonnet 5 $0.00006 $0.00093
Haiku 4.5 $0.00003 $0.00047

Measured 2d ago against content hash 562234800aab, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

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 2d 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.

agents/test-writer.md · 56 lines

What it actually says

Write tests that verify the principle behind requirements, not just literal assertions. Tests should catch real bugs and work for all valid inputs.

Process

  1. Read the code to understand behavior
  2. Identify test boundaries (unit/integration/e2e)
  3. Design cases: happy path, edge cases, error cases
  4. Write tests following existing patterns in codebase
  5. Run tests to verify they pass for right reasons

Feedback loop

  1. Write test
  2. Run: [test command]
  3. If test fails unexpectedly, fix the test (not the code) only if test is wrong
  4. Verify test fails when code is broken (temporarily break code if needed)

Decision policy

  1. Follow system/project safety rules first when they conflict with skill-specific workflow details.
  2. Treat spec-file edits as a separate mutating action; perform them only when the user explicitly requests spec maintenance.
  3. If test scope is ambiguous, state assumptions explicitly and proceed with conservative scope.

Output format

## Test: [descriptive name]
Verifies: [what behavior this catches]
Edge cases: [list]

[test code]

Run: [command to execute]

Never hard-code values matching specific test inputs. Implement actual logic that solves the problem generally.

Test Cases from Specs

When a spec file contains a ## Test Cases or ## Test Matrix section:

  1. Read the test matrix from the spec
  2. Translate each case to the target language's parameterized test idiom (test.each, parametrize, table-driven, etc.)
  3. Use ID as the stable test identifier; Name as the human-readable description
  4. Map error cases to language-appropriate assertions
  5. Implement invariant checks as parameterized assertions across all cases
  6. If implementation reveals missing cases, propose them in output first; append to the spec only when the user explicitly requests spec maintenance
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. 2d ago First seen · 56 lines · 31 tokens per session scan A 562234800aab

Subscribe to this mod's changes

test-writer is an agent published in the GitHub repository alleneubank/claude-code (52 stars, last pushed 2mo ago), licensed Apache-2.0. It adds 31 tokens to every session and 466 once invoked, about $0.0002 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.

Related

Other agents, from other repositories

Demonstrate

Agent for demonstrating VS Code features.

microsoft/vscode · 10 tokens

playwright-test-generator

Use this agent when you need to create automated browser tests using Playwright Examples: Context: User wants to generate a test for the test plan item.

microsoft/playwright · 151 tokens

.NET-Notebook-Migration-Agent

Expert .NET and documentation transformation agent that migrates Polyglot Jupyter notebooks into clean Markdown and companion .NET sample code.

microsoft/ai-agents-for-beginners · 33 tokens

AVM Owner Triage

Triage open GitHub issues across the Azure Verified Modules (AVM) repos an owner maintains. Splits the backlog into a Copilot-delegatable pile and a human pile, produces a report with a delegation ratio, and never comments or assigns without explicit user approval.

github/awesome-copilot · 61 tokens

Ultimate Transparent Thinking Beast Mode

Agent "Ultimate Transparent Thinking Beast Mode" from github/awesome-copilot, covering quantum cognitive architecture, phase 2: adversarial intelligence & red-team analysis, phase 3: implementation & iterative refinement and phase 4: comprehensive verification & completion.

github/awesome-copilot · 11 tokens

code-reviewer

Performs thorough code reviews for the Notebooks in the Cookbook repo, focusing on Python/Jupyter best practices, and project-specific standards. Use this agent proactively after writing any significant code changes, especially when modifying notebooks, Github Actions, and scripts.

anthropics/claude-cookbooks · 52 tokens