Vite

https://vitejs.dev/

Vite is a build tool for front-end web development that aims to provide a faster and more efficient development experience. It was created by Evan You, the same developer behind Vue.js. Vite (pronounced "veet") is often used as a development server for Vue.js applications, but it is not limited to Vue.js and can be used with other front-end frameworks or libraries.

Key features and aspects of Vite include:

1. Fast Development Server: Vite is known for its fast development server, which leverages native ES Module (ESM) support in modern browsers to provide quick module resolution and reduced build times.

2. Built-in Development Features: Vite comes with built-in development features such as hot module replacement (HMR) that enables real-time updates in the browser without a full page reload. This significantly speeds up the development feedback loop.

3. Vue.js Integration: While Vite is framework-agnostic and can be used with various front-end frameworks or libraries, it gained popularity in the Vue.js ecosystem. It is the recommended tool for Vue.js 3 development.

4. Native ES Module Support: Vite leverages native ESM support in browsers during development, eliminating the need for bundling during the development phase. This results in faster startup times and a more responsive development experience.

5. Plugin System: Vite has a plugin system that allows developers to extend or customize its behavior. This includes adding support for different file formats, tools, or enhancing the build process.

6. Optimized Build Process: In addition to the fast development server, Vite provides an optimized build process for production. It leverages Rollup for bundling and tree-shaking to generate efficient and minimal production builds.

7. TypeScript Support: Vite has built-in support for TypeScript, making it easy for developers to use TypeScript in their projects. TypeScript support includes type-checking during development and production builds.

8. CSS Pre-processors: Vite supports various CSS pre-processors like Sass, Less, and Stylus out of the box. These can be configured based on the project's preferences.

9. Customizable Configuration: While Vite comes with sensible defaults, developers can customize its configuration based on project requirements. The configuration file (vite.config.js) allows for fine-tuning various aspects of the build process.

10. Optimized for Modern Browsers: Vite is designed to take advantage of modern browser features and optimizations. This includes the use of native ES modules, dynamic imports, and other capabilities to optimize performance.

To start a new Vite project, developers typically use the Vite CLI to scaffold a project template and then customize it based on their needs. The simplicity, speed, and flexibility of Vite make it a popular choice for modern front-end development.

Vitest

https://vitest.dev/

Vitest is a modern unit testing framework designed for the Vite ecosystem, which is a build tool that aims to provide a faster and leaner development experience for modern web projects. Vitest is closely integrated with Vite, leveraging Vite's native ES modules support, fast cold start, and instant HMR (Hot Module Replacement) to offer a smooth testing experience.

Key Features of Vitest:

1. Fast Execution: Vitest takes advantage of Vite's fast module resolution and bundling capabilities, leading to quicker test runs.

2. ES Modules Support: It naturally supports ES modules, aligning with the modern JavaScript ecosystem.

3. Rich Assertion Library: Vitest includes a rich set of assertion methods, making it easy to write a variety of tests.

4. Built-in Mocking and Spying: It offers easy-to-use APIs for mocking and spying, which are essential for unit testing.

5. Parallel and Watch Mode: Tests can be run in parallel for efficiency, and it also supports a watch mode for rerunning tests on file changes.

6. TypeScript Support: Being part of the modern JavaScript toolchain, Vitest supports TypeScript out of the box.

7. Integration with Vite Plugins: It can utilize Vite plugins, allowing for advanced testing scenarios, like testing with specific build configurations or plugins.

8. Snapshot Testing: Vitest supports snapshot testing, which is useful for capturing the state of UI components or other complex data structures.

9. Compatible with Popular Testing Libraries: It works well with popular testing libraries like Jest, making it easier for developers to transition from other frameworks.

Vitest is particularly suitable for projects that are already using Vite, as it integrates seamlessly into the Vite ecosystem, providing a consistent developer experience from development to testing

To get started with Vitest, you can write a simple test that verifies the output of a function. For instance, if you have a function sum that adds two numbers, you can test it using Vitest as follows:

1. First, create the function in a file, say sum.js:

   export function sum(a, b) {
     return a + b;
   }

2. Then, write a test for this function in another file, like sum.test.js:

   import { expect, test } from 'vitest';
   import { sum } from './sum';
   
   test('adds 1 + 2 to equal 3', () => {
     expect(sum(1, 2)).toBe(3);
   });

Remember, by default, test files should have ".test." or ".spec." in their filenames. To execute the test, include a script in your package.json:

{
  "scripts": {
    "test": "vitest"
  }
}

Then, run the test using your package manager, like npm run test, yarn test, or pnpm test.

For configuring Vitest, you can use a vitest.config.ts file, or conditionally apply different configurations in your vite.config.ts. Vitest supports the same configuration file extensions as Vite, such as .js, .ts, .mjs, etc.

Vitest also offers various test utilities like test.concurrent for concurrent tests, test.todo for tests to be implemented later, test.fails for expected failures, and test.each for running the same test with different variables.

Moreover, Vitest includes features like benchmarks (bench), which allow you to define performance tests, and describe for organizing tests into suites.

For more details and advanced configurations, you can refer to the Vitest documentation:

• Getting Started with Vitest
• Vitest Configuration Guide
• Vitest API Reference

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Libraries

Vue Test UtilsTesting Library