[Feature Request] Explain the Testing apparatus

[mariomui]

While i sortah get the jest environment node setup , and the whole wss connecting to a specific node process running obsidian, there are bits of the testing apparatus that i dont understand namely the global[applyState] invocation, and how expects and actuals and coverage are implemented,filed, and analyzed.

Feature request would be an explanation of the testing process and how one would go about writing an example test.