HelpMeTest

MCP

How to Test MCP Tool Implementations: Schema, Handlers, and Error Propagation

Your MCP tool works in Claude Desktop. You've called it manually a dozen times. It returns results. You're confident. Then a user sends an unexpected input format, or calls two tools in sequence with shared state, or the downstream API your tool depends on returns a

MCP

Integration Testing MCP Servers End-to-End: Transports, Tool Calls, and Resource Listing

Unit tests for MCP tool handlers are necessary but not sufficient. They test the function — they don't test whether the server correctly handles the MCP protocol, whether tools are advertised correctly, whether resources are listed as expected, or whether the transport layer survives malformed messages. Integration tests do.

MCP

Testing MCP Server Authentication and Authorization: OAuth, Tokens, and Permission Scoping

Most MCP server tutorials skip authentication. The examples use stdio transport with no auth, the server runs locally, and there's nothing to secure. But if you're building an MCP server that exposes real capabilities — file access, database queries, API calls — and if that server is accessible

Test Automation

Vitest Browser Mode: Running Tests in Real Browsers vs jsdom

Vitest's browser mode runs your tests inside a real browser instead of a simulated DOM environment like jsdom or happy-dom. This matters because jsdom does not execute real JavaScript rendering, does not run CSS layout, and does not implement browser APIs like ResizeObserver, IntersectionObserver, or Web Components. When

Test Automation

Writing and Testing Custom Vite Plugins: Transforms, HMR, and Virtual Modules

Vite plugins extend the build pipeline with custom transforms, virtual modules, and build hooks. Testing them is harder than testing application code because a plugin's behavior is entangled with Vite's internals — module graphs, HMR events, rollup hooks. This guide covers a practical, reproducible approach to testing

Test Automation

Testing H3 and Nitro Server Routes: Event Handlers, Middleware, and Plugins

H3 is the HTTP framework that powers Nitro, which in turn powers Nuxt 3's server engine. If you write server/api/*.ts or server/routes/*.ts files in a Nuxt project, you are writing H3 event handlers. Testing these handlers in isolation — without starting a full Nuxt or

Test Automation

Testing Cloudflare Workers Locally with Miniflare and Wrangler

Cloudflare Workers run in V8 isolates, not Node.js. That difference means standard testing approaches break: node:fs, node:http, and most Node.js built-ins are unavailable. Miniflare solves this by implementing the Workers runtime APIs locally — KV, R2, D1, Durable Objects, Queues — so your tests run in an environment

Test Automation

Using Biome as an All-in-One Linter and Formatter in CI

Biome is a high-performance JavaScript and TypeScript toolchain that replaces ESLint, Prettier, and several other tools with a single binary. It is written in Rust, has near-zero configuration overhead, and runs lint checks 10–100× faster than the Node.js equivalents. This guide covers everything you need to integrate Biome

Test Automation

Testing Valtio Proxy State: subscribe, snapshot, Derived State, and React Integration

Valtio creates proxy state that you mutate directly. Its simplicity is also what makes testing it slightly unconventional — there's no dispatch, no reducers, and the proxy itself is mutable. The keys are using snapshot() for immutable assertions and subscribe() for testing reactive behaviour. Setup npm install valtio npm

Test Automation

Testing MobX Stores: Observables, Computed Values, Reactions, and Actions with Jest

MobX uses observable state, computed values, and reactions to build reactive systems. Testing MobX is straightforward because stores are plain classes with transparent state — no providers, no reducers, no dispatch. You call methods, read properties, and assert. Setup npm install mobx mobx-react-lite npm install -D jest @testing-library/react @testing-library/user-event

Test Automation

Testing Legend State: Observables, Computed, Persistence, and React Integration

Legend State is a high-performance state library built on a signals-based observable system. It's designed to minimize re-renders and handle large datasets efficiently. Testing it requires understanding how to read and write observables in tests, how to test computed values, and how to verify persistence. Setup npm install

Test Automation

Testing Zustand Stores: Actions, Selectors, Middleware, and Immer with Vitest

Zustand is a small, fast state management library with a minimal API. Its stores are plain JavaScript objects with actions — which makes them straightforward to test. The main challenges are resetting state between tests, testing middleware like persist and immer, and testing stores integrated with React components. Setup npm install