Slackbox — a Swoosh-style Slack library.
Define a notifier with use Slackbox.Notifier and send messages through it; a
per-environment adapter decides where they go: Slackbox.Adapters.Live (real
Slack) in prod, Slackbox.Adapters.Local (the fake Slack dev UI) in dev, and
Slackbox.Adapters.Test (with Slackbox.TestAssertions) in tests.
See Slackbox.Notifier and Slackbox.Message to get started.