Add NodeJS tests for client

[dmikey]

Client needs tests to check if it can run in a constrained environment (i.e. the JSC for React-Native).

[aamangupta]

can you tell more about more about this issue and let me work on this?

[ispedals]

This would be making test specifically for a react-native environment correct, as I don't think there's any other common environment that has limited implementation of Window and other browser globals.

I think the way to do this is to use Jest as the test runner and take the relevant pieces of react-native's configs for Jest to simulate running using JSC. The only downside of this is adding a dev dependency on jest just for this use case.