write-tests

A skill that creates unit and integration tests for a chosen file or function. It detects the project's test framework and covers normal cases, edge cases, errors, and asynchronous behavior; TDD means writing tests as part of developing a feature.

In plain words
What is it for?
Use it to add tests to existing code or create tests while developing a new module with TDD.
Why use it?
It reduces the effort of designing a thorough test set for code that has few or no tests.

Skill for Claude CodeCodex

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 skills/viknesh20-20/claude-code-tool-kit/write-tests
Any agent
npx skills add viknesh20-20/claude-code-tool-kit --skill write-tests
Clone the repo
git clone --depth 1 https://github.com/viknesh20-20/claude-code-tool-kit

Made for: Claude Code, Codex.

Per session 60 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 926 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 $0.00060 $0.00926
Opus 5 $0.00030 $0.00463
Sonnet 5 $0.00012 $0.00185
Haiku 4.5 $0.00006 $0.00093

Measured 2d ago against content hash 3b5ae58b3249, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

write-tests 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.

.claude/skills/write-tests/SKILL.md · 96 lines

How it starts

The opening of the file, as written. The whole thing — 96 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Write Tests

Detect Project Test Environment

Package/Project Files

!ls package.json pytest.ini pyproject.toml setup.cfg tox.ini go.mod Cargo.toml *.csproj *.sln Gemfile build.gradle pom.xml mix.exs deno.json 2>/dev/null

Existing Tests

!find . -type f \( -name "*.test.*" -o -name "*.spec.*" -o -name "test_*" -o -name "*_test.*" -o -name "*_spec.*" -o -name "*Test.*" -o -name "*Spec.*" \) -not -path "*/node_modules/*" -not -path "*/.git/*" -not -path "*/vendor/*" 2>/dev/null | head -20

Test Config

!cat jest.config.* vitest.config.* pytest.ini pyproject.toml setup.cfg .rspec 2>/dev/null | head -50


Instructions

Step 1: Analyze the Target

  1. Read the file or function to be tested
  2. Identify all public APIs, functions, methods, and classes
  3. Map out the code paths: conditionals, loops, error throws, early returns
  4. Identify external dependencies that need mocking

Step 2: Determine Test Framework

Based on the detected project files:

  • JavaScript/TypeScript: Jest, Vitest, Mocha, or Playwright (check package.json)
  • Python: pytest, unittest (check pyproject.toml, pytest.ini)
  • Go: standard testing package
  • Rust: built-in #[cfg(test)] module
  • C#/.NET: xUnit, NUnit, or MSTest
  • Ruby: RSpec or Minitest
  • Java: JUnit 5 or TestNG
  • Elixir: ExUnit

Step 3: Follow Existing Patterns

  • Find the nearest existing test file for a similar module
  • Match the structure: describe/it, test classes, test functions
  • Match the mocking approach: jest.mock, unittest.mock, testify, etc.
  • Match the assertion style: expect, assert, should
  • Match the file naming convention and directory placement

Step 4: Generate Tests

Write tests covering ALL of the following categories:

Happy Path
  • Normal inputs produce expected outputs
  • Standard use cases work correctly
  • Return values and side effects are verified
Edge Cases
  • Empty inputs (null, undefined, empty string, empty array, zero)
  • Boundary values (min, max, off-by-one)
  • Unicode and special characters where relevant
  • Large inputs (performance boundary)

Read the full file on GitHub · 96 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. 2d ago First seen · 96 lines · 60 tokens per session scan A 3b5ae58b3249

Subscribe to this mod's changes

write-tests is a skill published in the GitHub repository viknesh20-20/claude-code-tool-kit (7 stars, last pushed 4mo ago), licensed MIT. It adds 60 tokens to every session and 926 once invoked, about $0.0003 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 2026-08-31.

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