running-and-testing

name	running-and-testing
description	Builds, runs, and tests the Latch Desktop Electron app. Covers dev mode, production builds, type checking, unit tests, linting, and native module gotchas. Use when you need to run, build, or verify the application.

Running and Testing

Latch Desktop is an Electron app built with electron-vite (three separate Vite builds: main, preload, renderer).

Quick reference

Command	What it does
npm install	Install deps + rebuild native modules (node-pty, better-sqlite3)
npm run dev	Launch app with HMR
LATCH_DEVTOOLS=1 npm run dev	Launch with DevTools open
npm run build	Production build → out/
npx tsc --noEmit -p tsconfig.node.json	Type-check main + preload
npx tsc --noEmit -p tsconfig.web.json	Type-check renderer
npx vitest run	Run all tests once
npx vitest run src/main/services/my.test.ts	Run a single test file
npm run lint	ESLint check
npm run format	Prettier format

Development

npm install          # Must run first — triggers electron-rebuild
npm run dev          # Opens the app with Vite HMR for renderer

The renderer loads from the Vite dev server (hot reload). Main and preload rebuild on save.

Type checking

Two tsconfig files target different environments:

• tsconfig.node.json — main process + preload (CommonJS, ES2022, Node types)
• tsconfig.web.json — renderer (ESNext, React JSX, DOM types)

Always check both:

npx tsc --noEmit -p tsconfig.node.json && npx tsc --noEmit -p tsconfig.web.json

Testing

Tests use vitest and live next to source files:

src/main/services/authz-server.test.ts
src/main/services/radar.test.ts

Run all tests:

npx vitest run

Run one file:

npx vitest run src/main/services/authz-server.test.ts

Watch mode:

npx vitest --watch

Test conventions

• Import { describe, it, expect } from vitest
• Create factory helpers for test fixtures (makePolicy(), makeEvent())
• Group related tests with nested describe blocks
• Test pure exported functions directly

Production build

npm run build

Outputs to out/:

• out/main/index.js — main process bundle
• out/preload/index.js — preload bundle
• out/renderer/index.html + assets — renderer bundle

Native module warning

node-pty and better-sqlite3 are compiled for Electron's Node ABI via electron-rebuild (runs automatically on npm install).

Do NOT test them with system Node — they will crash with a version mismatch error. Always test inside the running app with npm run dev.

If you see NODE_MODULE_VERSION mismatch errors after switching Node versions:

npm run postinstall    # re-runs electron-rebuild

Build architecture

electron-vite produces three independent Vite builds:

Build	Entry	Output	Module
main	src/main/index.ts	out/main/index.js	SSR (CommonJS)
preload	src/preload/index.ts	out/preload/index.js	SSR (CommonJS)
renderer	src/renderer/main.tsx	out/renderer/	Client (ESM)

Native modules (node-pty, better-sqlite3) are externalized via externalizeDepsPlugin() — they're loaded at runtime, not bundled.

Verification after changes

After modifying source files, run this to confirm nothing is broken:

npx tsc --noEmit -p tsconfig.node.json && npx tsc --noEmit -p tsconfig.web.json && npx vitest run && npm run build