Lots of gems throw warnings!

test.txt

$ rake test
/opt/rubies/2.0.0-p0/bin/ruby -I"lib:test" -w -I"/Users/steve/.gem/ruby/2.0.0/gems/rake-10.0.4/lib" "/Users/steve/.gem/ruby/2.0.0/gems/rake-10.0.4/lib/rake/rake_test_loader.rb" "test/map_stream_test.rb" "test/map_test.rb" "test/merge_test.rb" "test/mvp_test.rb" "test/on_value_test.rb" "test/select_test.rb"
/Users/steve/.gem/ruby/2.0.0/gems/simplecov-html-0.7.1/lib/simplecov-html.rb:57: warning: assigned but unused variable - title_id
/Users/steve/.gem/ruby/2.0.0/gems/coveralls-0.6.7/lib/coveralls.rb:66: warning: `&' interpreted as argument prefix
/Users/steve/.gem/ruby/2.0.0/gems/coveralls-0.6.7/lib/coveralls.rb:72: warning: `&' interpreted as argument prefix
/Users/steve/.gem/ruby/2.0.0/gems/rest-client-1.6.7/lib/restclient/exceptions.rb:157: warning: assigned but unused variable - message
/Users/steve/.gem/ruby/2.0.0/gems/rest-client-1.6.7/lib/restclient/exceptions.rb:167: warning: assigned but unused variable - message
/Users/steve/.gem/ruby/2.0.0/gems/rest-client-1.6.7/lib/restclient/response.rb:11: warning: method redefined; discarding old body
/Users/steve/.gem/ruby/2.0.0/gems/rest-client-1.6.7/lib/restclient/payload.rb:47: warning: mismatched indentations at 'end' with 'case' at 40
[Coveralls] Set up the SimpleCov formatter.
[Coveralls] Using SimpleCov's default settings.
/Users/steve/.gem/ruby/2.0.0/gems/coveralls-0.6.7/lib/coveralls.rb:83: warning: instance variable @testing not initialized
[Coveralls] Outside the Travis environment, not sending data.
/Users/steve/.gem/ruby/2.0.0/gems/coveralls-0.6.7/lib/coveralls.rb:96: warning: instance variable @noisy not initialized
/Users/steve/.gem/ruby/2.0.0/gems/simplecov-0.7.1/lib/simplecov/defaults.rb:57: warning: instance variable @exit_status not initialized
Run options: --seed 34854

# Running tests:

............

Finished tests in 0.003381s, 3549.2458 tests/s, 6506.9506 assertions/s.

12 tests, 22 assertions, 0 failures, 0 errors, 0 skips

Or as a one-liner:

$ RUBYOPT=-w rake test

Less is more, and all that! 😄