Unit testing setup

[blenderskool]

Unit testing setup with possibly Vitest for the compiler and editor module that will allow us to write unit tests for different parts of the codebase.

Why Vitest

• Works out-of-the-box with TypeScript.
• Has similar syntax to Jest.
• Editor already uses Vite, so using Vitest makes sense.
• Has UI and extensions with IDEs to interactively run tests.