typescript-test

name

typescript-test

description

Provides Vitest-based TypeScript testing expertise and best practices. Ensures proper test structure, mocking strategies, async handling patterns, and coverage optimization. Specializes in unit testing, integration testing, test organization with describe/it blocks, vi.mock patterns, snapshot testing, and testing library integration for UI components. Use when: writing TypeScript test files (.spec.ts, .test.ts), structuring tests with describe/it/test blocks, implementing mocks with vi.mock/vi.spyOn, testing async code with async/await or promises, creating test fixtures and helpers, implementing snapshot tests, testing React components with Testing Library, measuring and improving code coverage, or configuring Vitest for TypeScript projects.

TypeScript Testing Code Guide

Test File Structure

One-to-one matching with the file under test. Test files should be located in the same directory as the target file.

File Naming

Format: {target-file-name}.spec.ts.

Example: user.service.ts → user.service.spec.ts

Test Framework

Use Vitest. Maintain consistency within the project.

Test Hierarchy

Organize by method (function) unit as major sections, and by test case as minor sections. Complex methods can have intermediate sections by scenario.

Test Coverage Selection

Omit obvious or overly simple logic (simple getters, constant returns). Prioritize testing business logic, conditional branches, and code with external dependencies.

Test Case Composition

At least one basic success case is required. Focus primarily on failure cases, boundary values, edge cases, and exception scenarios.

Test Independence

Each test should be executable independently. No test execution order dependencies. Initialize shared state for each test.

Given-When-Then Pattern

Structure test code in three stages—Given (setup), When (execution), Then (assertion). Separate stages with comments or blank lines for complex tests.