# Code Testing Agent

> Suggests purpose-driven tests tied to actual behavior. Writes test files covering untested paths and behavior gaps in the codebase. Use when the user asks to suggest tests or find untested behavior.

- Skill: `shawn-sandy/code-testing-agent` (Agent Skill, multi-file: 5 files)
- Install (CLI): `npx skillmds@latest add shawn-sandy/code-testing-agent`
- Raw SKILL.md: https://api.skillmd.com/api/skills/shawn-sandy/code-testing-agent/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- License: MIT
- Author: shawn-sandy (https://skillmd.com/u/shawn-sandy)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/shawn-sandy/code-testing-agent

---


---

Analyze code and suggest specific, purpose-driven tests tied to actual behavior.
Strive to meet the project's coverage target, or maximize coverage when no
target is defined.

> **Freedom level: Flexible** — Follow these steps in order. Adapt depth to the
> code's complexity and the user's request.

## When not to use

Does not run tests — use running-tests. Does not review code quality — use code-review-agent.

## Table of Contents

- [Step 0 — Create Progress Todos](#step-0--create-progress-todos)
- [Step 1 — Identify Target Code](#step-1--identify-target-code)
- [Step 2 — Search for Implementation Plan](#step-2--search-for-implementation-plan)
- [Step 3 — Analyze the Code](#step-3--analyze-the-code)
- [Step 4 — Detect Project Test Infrastructure](#step-4--detect-project-test-infrastructure)
- [Step 5 — Suggest Tests with Rationale](#step-5--suggest-tests-with-rationale)
- [Step 6 — Offer to Write Test Files](#step-6--offer-to-write-test-files)

---

## Step 0 — Create Progress Todos

Use `TodoWrite` to create todos for Steps 1–6 (all `status: "pending"`). Mark
each `status: "completed"` as you finish.

---

## Step 1 — Identify Target Code

Resolve the target code using this priority order. Load
`references/input-resolution.md` for detailed parsing heuristics.

1. **File path argument** — parse the invocation message for a file path
2. **Function/method argument** — note any named function; scope Step 3 to it
   once a file is resolved
3. **Pasted code** — use the inline code block as an anonymous file
4. **Conversation context** — recently created, edited, or discussed file
5. **Recent changes** — `git diff --name-only HEAD~1` (exclude test/config/lock
   files); confirm with user
6. **Ask** — "Which code would you like me to suggest tests for?"

Report: file(s) to analyze, function scope if any, full-file vs. scoped. Read
each target file in full.

---

## Step 2 — Search for Implementation Plan

Search for design intent (stop at first match):

1. User's message
2. `docs/plans/` — match by filename similarity to target code
3. `~/.claude/plans/` — same matching logic
4. `git log --oneline -5` — commit messages describing intent
5. Inline `// TODO`, `// PLAN:`, `// PURPOSE:`, or JSDoc `@description` in the
   target code

If found: report
`"Found plan: [path]. Using it to understand intended behavior."` Extract goal,
key behaviors, edge cases, and acceptance criteria.

If not found: report
`"No implementation plan found. Inferring intent from code and context."`
Proceed to Step 3.

---

## Step 3 — Analyze the Code

Load `references/test-analysis-guide.md` for detailed heuristics. Analyze:

- **3a. Behavioral summary** — 2–4 sentences on purpose and primary behavior
- **3b. Critical paths** — happy path, error paths, branching logic, state
  transitions
- **3c. Integration points** — external APIs, file system, events, internal
  modules, env config
- **3d. Implicit contracts** — return shape, side effects, ordering, idempotency
  guarantees
- **3e. Fragility** — complex conditionals, regex, math, null chains, index
  arithmetic

---

## Step 4 — Detect Project Test Infrastructure

Load `references/test-infrastructure.md` for config file locations and glob
patterns. Detect:

- **4a. Test framework** — from `package.json`, `pytest.ini`, `Cargo.toml`, CI
  config, etc.
- **4b. Existing test files** — glob for `*.test.*`, `*.spec.*`, `*_test.*` near
  the target
- **4c. Existing patterns** — read 1–2 test files for import style, mocking,
  conventions
- **4d. Coverage target** — from `jest.config.*`, `pyproject.toml`, `.nycrc`,
  `codecov.yml`

Report:
`"Detected: [framework]. Existing tests use [patterns]. Coverage target: [X]%."`

---

## Step 5 — Suggest Tests with Rationale

Load `references/output-guide.md` for the full output template and suggestion
principles.

For each suggestion provide: **What** (behavior), **Why** (blast radius if
missing), **How** (approach + key assertions), **Where** (file path). Group by
file; prioritize by blast radius.

---

## Step 6 — Offer to Write Test Files

Ask: "Would you like me to write the test file(s)? I will create [path(s)] with
the tests above."

- **Yes** — write complete files using detected conventions (Priority 1 + 2;
  confirm before including Priority 3). Suggest `[test command]` to verify.
- **No** — "The suggestions above should give you a clear starting point."
- **Partial** — write only the requested subset.