Update CONTRIBUTING.md to specify starting Redis

[seanprashad]

My Node version is 12.12.0 and my operating system is Mac OS Catalina 10.15.1 (19B88).

As a new individual to telescope, I was trying to setup the project using the steps listed under Setup found here.

However, an error occurred after step 5 (5. Run npm test) which states that the able to add a job to the feed queue test failed due to connect ECONNREFUSED 127.0.0.1:6379.

After grepping the repo for the port 6379, I realized that I had not started the Redis container using docker-compose up -d docker-compose up -d redis. It would be great to include that command in our CONTRIBUTING.md docs before Run npm install.

[seanprashad]

I'll be happy to submit a patch for this 🦧

[seanprashad]

As these are unit tests, it might be helpful to use redis-mock to simulate a running instance of Redis to avoid this problem in the future.

[humphd]

#122 is related to this as well. A lot of people are stumbling on this. We should fix it in a few ways (docs, better error message, etc).

redis-mock is interesting. We could consider this, but we're already running Redis in CI, so it's not critical. Probably worth filing another issue on it at least. The work in #71 could likely benefit from it in testing as well.