Include arbitrary modules with Ruby.

harness.rb

# Use this class to test an arbitrary module.
class Harness
  def initialize(_module)
    self.class.include _module
  end
end

###

# The module being tested
module ToBeTested
  def foo
    "foo!"
  end
end

harness = Harness.new(ToBeTested)
harness.foo # => "foo!"