module ThoughtBot::Shoulda::Assertions

assert_contains(['a', '1'], /not there/) => fails
assert_contains(['a', '1'], 'a') => passes
assert_contains(['a', '1'], /\d/) => passes

at least one element from the collection matches x. +extra_msg+ is appended to the error message if the assertion fails.
Asserts that the given collection contains item x. If x is a regular expression, ensure that

def assert_contains(collection, x, extra_msg = "")
  collection = [collection] unless collection.is_a?(Array)
  msg = "#{x.inspect} not found in #{collection.to_a.inspect} #{extra_msg}"
  case x
  when Regexp
    assert(collection.detect { |e| e =~ x }, msg)
  else         
    assert(collection.include?(x), msg)
  end
end