Our review

Generates bun:test unit tests for a TypeScript file in a Next.js project, extending an existing test file instead of overwriting it.

Follows project conventions: bun:test imports and co-located .test.ts/.test.tsx files next to the source
Non-destructive: reads the existing test file and only adds missing cases (untested functions, branches, scenarios)
Covers happy path, edge cases, and error scenarios, mocking external dependencies such as fetch, store, database calls, and crypto.randomUUID
Adapts to the file type: API route handlers invoked directly with mock Request objects, or pure-logic and event-handling tests for React components

Tied to the Next.js + TypeScript + bun:test stack and not directly usable with Jest or Vitest
Component tests depend on @testing-library/react being available and otherwise fall back to testing extracted pure logic
Snapshot testing is excluded by design, and structural files (layout.tsx, page.tsx, globals.css) are skipped entirely

When to use it

Use it when you want to quickly add or complete unit tests for a specific source file in a Next.js project running on Bun.

When not to use it

Avoid it on projects that do not use bun:test or Next.js, or when what you actually need is integration or end-to-end coverage.

name: test description: Generate unit tests for a file in a Next.js TypeScript project using bun:test. Accepts a file path, reads the source, creates focused tests covering happy path, edge cases, and error scenarios. Checks for an existing test file and only adds missing tests. Follows project conventions (bun:test, co-located .test.ts/.test.tsx files).

Test Generator

Generates unit tests for Next.js TypeScript files using Bun's built-in test runner (bun:test).

/test components/IssueCard.tsx
/test lib/store.ts
/test app/api/issues/route.ts

The path is relative to the project root (no leading / needed).

Accepts a file path — the user provides a path to a source file (e.g., components/IssueCard.tsx)
Resolves the full path — joins the project root with the provided path
Reads the source file — understands the logic, types, dependencies, and patterns
Checks for an existing test file — looks for {basename}.test.ts or {basename}.test.tsx next to the source
If no test file exists — creates one with comprehensive tests
If a test file exists — reads it, determines what's missing (untested functions, branches, scenarios), and adds only the missing test cases (never overwrites)
Writes the test file — co-located beside the source

Import from bun:test: import { describe, it, expect, beforeEach, mock, spyOn } from "bun:test"
describe blocks to group related tests
Clear test names that describe the scenario and expected outcome (e.g., "returns the issue when it exists")
Happy path, edge cases, and error scenarios
Mock external dependencies: fetch, store, database calls, Next.js response objects
Mock crypto.randomUUID() for deterministic IDs in store tests
For React components: render with @testing-library/react if available, or keep tests focused on pure logic extraction and event handling
For API routes: test request/response behavior by invoking the handler directly with mock Request objects
No snapshot testing
Use expect().toBe() / toEqual() / toThrow() / toBeNull() / toBeUndefined()

globals.css, layout.tsx, page.tsx — these are structural bootstrapping files with little testable logic
node_modules files
Test files themselves (.test.ts / .test.tsx)