I'm trying to debug someone else's code and having trouble figuring out what's wrong. When I run rake, one of the errors I get is:

  2) Error:
test_math(TestRubyUnits):
NoMethodError: undefined method `unit_sin' for CMath:Module
    /home/user/ruby-units/lib/ruby_units/math.rb:21:in `sin'

This is the function that calls the method:

assert_equal Math.sin(pi), Math.sin("180 deg".unit)

And this is what the class looks like:

module Math
  alias unit_sin sin
  def sin(n)
    Unit === n ? unit_sin(n.to('radian').scalar) : unit_sin(n)
  end

  alias unit_cos cos
  def cos(n)
    Unit === n ? unit_cos(n.to('radian').scalar) : unit_cos(n)
  end

  ...

  module_function :unit_sin
  module_function :sin
  module_function :unit_cos
  module_function :cos
  ...

end

(The ellipsis means "more of the same"). As far as I can see, this is valid Ruby code. Is there something I'm missing here that's causing the error, or could the error be coming from something else?

Update: I'm wondering if the problem has to do with namespaces. This code is attempting to extend CMath, so perhaps the alias and/or module_function isn't actually getting into CMath, or something like that....