task: #20 Replace Jest with Vitest

[ksolanki7]

Background

For better test performance, Vitest is much faster than Jest, Vitest is built on Vite, which makes it significantly faster than Jest. It uses esbuild (a super-fast bundler) instead of Babel or Webpack for transforming code. It performs parallel test execution and worker threads which improves test performance.

Jest was designed for CommonJS, while Vite and Vitest are ESM first tools.

This PR includes

• Replaces Jest with Vite + Vitest
• Installed HappyDom (Again performance improvement)
• As Vitest and Jest have similar APIs, they are not the same, the following changes are made to support Vitest.
  • jest.fn -> vi.fn, jest.mock -> vi.mock
• Avoid capturing RTL internals in DOM snapshot, for more details reference this PR context

Note:
As part of the changes, I have updated all the test cases in one go, so most changes will be snapshot updates that can be ignored. To ease things up for the reviewer, I have left inline PR comments to facilitate any relevant changes.

[ksolanki7]

Removed Jest related configs

[ksolanki7]

Vitest doesn't natively include all the matchers that Jest provides, particularly those related to the DOM like toBeInTheDocument(), toHaveClass, toHaveAttribute and etc. So we are using @testing-library/jest-dom to take advantage of Jest matchers.

[ksolanki7]

No requirement for typeRoots here as by default Typescript automatically searches for type definitions inside node_modules/@types, we should only be configuring typeRoots if we want to specify any specific directory.

[ksolanki7]

Jest overwrites axios completely, which works in Jest's ecosystem while Vitest requires preserving the original module and explicitly mocking only the needed parts.

• In Jest, jest.mock('axios', () => ({ get: jest.fn() })) replaces the entire axios module with an object containing only a get method as a mock.
• In Vitest, vi.mock('axios', async (importOriginal) => { ... }) ensures that the original axios module is imported before modifying it.

[ksolanki7]

Migrating from Jest to Vitest, we need to replace requireActual with importActual.
Ref: https://vitest.dev/guide/migration.html#importing-the-original-of-a-mocked-package

[kurtdoherty]

Nice one 👍

[kurtdoherty]

note: We've documented our TS configs here. No need to follow suit in this PR, but I think this is another thing we could standardise on via a separate repo in future.