tests: figure out a way to not actually hit the CoinGecko endpoint in a test context

[Zidious]

We should really not hit a live GET endpoint while testing locally or through the github action.

Potential solutions:

1. use Nock to intercept the endpoint (this may not work outside of a testing context as we are using a CLI)
2. a local server that can mimic the response from the endpoint provided by the API, although we have no way to set the URL within the CLI or API package

[stephenmathieson]

A 3rd potential solution is Talkback. I've used its predecessor (yakbak, appears dead) in the past, which worked well.