database.yml

test:
  adapter: sqlite3
  database: ":memory:"

test_helper.rb

def shhhh(&block)
  old_output, $stdout = $stdout, StringIO.new
  yield
ensure
  $stdout = old_output
end

shhhh do # Need for SQLite, in-memory DB only
  load File.join(File.dirname(__FILE__), '../db/schema.rb')
end