name: write-unit-test description: > Workflow for adding Jest unit tests to iinkTS. Use when creating tests for new or existing src/ files. Complements the testing-patterns skill (patterns reference). This skill covers the workflow; the testing-patterns skill covers the API reference. metadata: version: "1.0.0"

Write Unit Test

Workflow

1. Find the mirror path

Test file = test/unit/ + same path as src/:

src/manager/interactive/IIWriterManager.ts
→ test/unit/manager/interactive/IIWriterManager.test.ts

If the test file doesn't exist yet, create it. Never put tests elsewhere.

2. Load the patterns reference

Before writing, invoke the testing-patterns skill for:

• Mock setup (Canvas, WebSocket, fetch)
• Standard describe/it structure
• Available mocks: createCanvasMock/asCanvas, InteractiveInkSSRCanvasMock, CanvasEventMock, ServerWebSocketMock, etc.

3. Structure the test file

import { describe, test, expect, beforeEach, jest } from "@jest/globals"
import { ClassOrFunction } from "@/path/to/module"
describe("ClassName", () => {
  describe("methodName", () => {
    test("should [expected] when [condition]", () => {
      // Arrange
      // Act
      // Assert
    })
  })
})

4. Cover minimum cases per function

For every public function/method:

• ✅ Nominal — valid input, expected output
• ✅ Error — invalid/null/undefined input
• ✅ Edge — empty array, zero, boundary values
• ✅ Side effects — if the function mutates state or emits events

5. Coverage check

yarn test:unit --coverage --testPathPatterns="YourFile"

Target: ≥80% branches, functions, lines for new files.

Full suite check before commit:

yarn test:unit

Quick Rules

• No `any` in tests — type your mocks explicitly
• No implementation details — test behavior, not internals
• Isolate — each test should pass independently (no shared mutable state between tests)
• Mock at boundaries — mock Canvas, WebSocket, fetch. Never mock the class under test itself.
• One assertion focus per test — multiple expect OK if they describe one behavior

See Also

The testing-patterns skill — full mock API reference, WebSocket patterns, Playwright E2E patterns.