UPDATE 2015-12-04 : Tinytest is now documented, for the upcoming Meteor 1.3 release. See the official README.md. Better use the official information than my unofficial cheatsheet.
I've been doing a lot more Meteor these days, especially working on Drupal 8 SSO with Meteor, and could not find a reasonably complete and up-to-date (for Meteor 188.8.131.52) list of the Tinytest assertions, so I updated, reordered, and completed the existing gist on the topic.
So here is the Meteor Tinytest cheatsheet: : complete list of assertions and helpers for your test methods.