module RSpec::Mocks::TestDouble

def self.extend_onto(object, name=nil, stubs={})

module.foo #=> "bar"
RSpec::Mocks::TestDouble.extend_onto(module, "MyMixin", :foo => "bar")
module = Module.new

@example

initializes it as a test double.
Extends the TestDouble module onto the given object and 
def self.extend_onto(object, name=nil, stubs={})
  object.extend self
  object.send(:__initialize_as_test_double, name, stubs)
end