Since this is merged already, I guess these comments are for a PR after Manjula merges her work. Suggestions:
Rename BaseTest to be more descriptive of its single purpose (allowing guice injection).
Rename Helpers classes to something slightly more descriptive (Actions? I can't think of a good name, but I think helper is too vague).
Split HubHelper out into webhook and channel (and maybe split out actions from assertions if there's clean separation). If the file is 140 lines after a couple of tests, that's gonna be a monster class.
Since this is merged already, I guess these comments are for a PR after Manjula merges her work. Suggestions: