module ThoughtBot::Shoulda::Private

def get_options!(args, *wanted)

Will raise if there are keys in the args hash that aren't listed.
Returns the values for the entries in the args hash who's keys are listed in the wanted array.
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def get_options!(args, *wanted)
  ret  = []
  opts = (args.last.is_a?(Hash) ? args.pop : {})
  wanted.each {|w| ret << opts.delete(w)}
  raise ArgumentError, "Unsupported options given: #{opts.keys.join(', ')}" unless opts.keys.empty?
  return *ret
end

def model_class

class TestUser; model_class; end => User

Returns the model class constant, as determined by the test class name. 
def model_class
  self.name.gsub(/Test$/, '').constantize
end