Test-First-Ruby bug in calculator exercise?

Question

I'm going through the Test-First-Ruby exercises, but I've hit an error that seems like a bug:

Failures:

1) add adds 0 and 0 Failure/Error: add(0,0).should == 0 NoMethodError: undefined method add' for #<RSpec::Core::ExampleGroup::Nested_1:0x007fdd890bab08> # ./spec/02_calculator.rb:42:inblock (2 levels) in '

I understand it can't find the 'add' method, but here's what my /test-first-ruby/lib/02_calculator.rb file looks like:

def add(num1,num2)
  new_num = num1 + num2
end

I don't understand what I'm doing wrong.