Problem:

In T140352#2496343, @jhobs wrote:

We don't really document our process for making contributions very well. We have sections in README.md that explain tests and commits, but some aren't especially well-written. As an example, I tried following the instructions for running tests [on MobileFrontend] and was immediately met with an error and nowhere to go for troubleshooting (if I were a first-time volunteer who didn't know about #wikimedia-mobile on IRC). In order to help onboard new devs and encourage volunteer contributions, I think we should refactor the top of README.md to be a bit more "how-to", or have another document in the repo to describe how to get started. If we decide on a new document I'd recommend CONTRIBUTIONS.md or CONTRIBUTIONS.mediawiki, the latter of which could correspond to a page on mediawiki.org.

As AC, the following statement should be true:
As a new contributor with only a fresh vagrant instance and a gerrit account, I should be able to follow the steps in README.md (or CONTRIBUTIONS.md) to drive a change from start to finish, including running tests.