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132 lines
3.1 KiB
Markdown
132 lines
3.1 KiB
Markdown
---
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title: In-Source Testing | Guide
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---
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# In-Source Testing
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Vitest provides a way to run tests within your source code along side the implementation, similar to [Rust's module tests](https://doc.rust-lang.org/book/ch11-03-test-organization.html#the-tests-module-and-cfgtest).
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This makes the tests share the same closure as the implementations and able to test against private states without exporting. Meanwhile, it also brings a closer feedback loop for development.
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::: warning
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This guide explains how to write tests inside your source code. If you need to write tests in separate test files, follow the ["Writing Tests" guide](/guide/#writing-tests).
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:::
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## Setup
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To get started, put a `if (import.meta.vitest)` block at the end of your source file and write some tests inside it. For example:
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```ts [src/index.ts]
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// the implementation
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export function add(...args: number[]) {
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return args.reduce((a, b) => a + b, 0)
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}
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// in-source test suites
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if (import.meta.vitest) {
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const { it, expect } = import.meta.vitest
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it('add', () => {
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expect(add()).toBe(0)
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expect(add(1)).toBe(1)
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expect(add(1, 2, 3)).toBe(6)
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})
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}
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```
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Update the `includeSource` config for Vitest to grab the files under `src/`:
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```ts [vitest.config.ts]
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import { defineConfig } from 'vitest/config'
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export default defineConfig({
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test: {
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includeSource: ['src/**/*.{js,ts}'], // [!code ++]
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},
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})
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```
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Then you can start to test!
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```bash
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$ npx vitest
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```
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## Production Build
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For the production build, you will need to set the `define` options in your config file, letting the bundler do the dead code elimination. For example, in Vite
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```ts [vite.config.ts]
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/// <reference types="vitest/config" />
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import { defineConfig } from 'vite'
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export default defineConfig({
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test: {
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includeSource: ['src/**/*.{js,ts}'],
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},
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define: { // [!code ++]
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'import.meta.vitest': 'undefined', // [!code ++]
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}, // [!code ++]
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})
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```
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### Other Bundlers
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::: details unbuild
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```ts [build.config.ts]
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import { defineBuildConfig } from 'unbuild'
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export default defineBuildConfig({
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replace: { // [!code ++]
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'import.meta.vitest': 'undefined', // [!code ++]
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}, // [!code ++]
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// other options
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})
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```
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Learn more: [unbuild](https://github.com/unjs/unbuild)
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:::
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::: details Rollup
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```ts [rollup.config.js]
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import replace from '@rollup/plugin-replace' // [!code ++]
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export default {
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plugins: [
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replace({ // [!code ++]
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'import.meta.vitest': 'undefined', // [!code ++]
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}) // [!code ++]
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],
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// other options
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}
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```
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Learn more: [Rollup](https://rollupjs.org/)
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:::
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## TypeScript
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To get TypeScript support for `import.meta.vitest`, add `vitest/importMeta` to your `tsconfig.json`:
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```json [tsconfig.json]
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{
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"compilerOptions": {
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"types": [
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"vitest/importMeta" // [!code ++]
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]
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}
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}
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```
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Reference to [`examples/in-source-test`](https://github.com/vitest-dev/vitest/tree/main/examples/in-source-test) for the full example.
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## Notes
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This feature could be useful for:
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- Unit testing for small-scoped functions or utilities
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- Prototyping
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- Inline Assertion
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It's recommended to **use separate test files instead** for more complex tests like components or E2E testing.
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