Change store.initailize execution hook from useMemo to useEffect and add test for useInitializeExpoRouter

[naporin0624]

Motivation

This PR proposes a modification in the interaction between the singleton "RouteStore" and React. Currently, the useMemo hook is being utilized, which is typically used for caching values (useMemo documentation). This PR suggests that the useEffect hook might be more suitable for this context, as detailed in its documentation.

Execution

To realize the proposed change, i undertook the following steps:

• Split the global-state.tsx file to facilitate the mocking of the store singleton, which was challenging with jest.mock.
• Modified useMemo to useEffect in useInitializeExpoRouter to ensure alignment with the proposed integration strategy.
• Conducted tests to verify the unchanged behavior of useInitializeExpoRouter post-modification.

Test Plan

To substantiate these modifications, a comprehensive test plan has been devised. The testing strategy underscores:

• Validating that the store.initialize function is initiated exclusively when alterations occur in the context or location, reinforcing the stability and efficiency of the system.
• Confirming the precise invocation of the useExpoRouter function to maintain seamless connectivity and functionality.

The following strategies were employed during the testing phase:

1. The store.initialize function was monitored to ensure it is called when there is a change in reference and context, further validated by rerendering with new context and location values.
2. Observations were made to ascertain that the store.initialize function is not called repetitively when the same context is passed, fostering system efficiency.

These strategies were systematically executed using the renderHook function alongside the implementation of mock functions to mimic the behavior of the store.initialize and store.subscribeToStore methods, thereby offering a robust and reliable testing framework.

[marklawlor]

useEffect fires after the initial render, meaning the store will be initialised too late. If you use useEffect you'll now have two renders, one where no routes are rendered and then a second once the store is initialised.

[naporin0624]

Thank you for taking a look.

It was good to learn more about why you are running side effects in useMemo.