Online reading for anonymous functions, unit testing, and distributed version control system (DVCS)

Test::Unit

WikiBook Ruby unit testing: a simple number test example, list of avaible assertations, setup/teardown

Rspec

Relish page on rspec-core: get-started example at the end (test driven development), shared examples and contexts

Anonymous functions

Ruby Procs and Lambdas and the difference by Alan Skorkin: good descriptions and examples, plus a picture of "first class"

Distributed version control

Illustrated intro by Kalid Azad: diagrams, key concepts and properties, Mercurial (hg) commands

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