I agree with others that just calling upcase should be disallowed.
Especially since you disallowed the use of alias_method.
If you are going to disallow this then you should disallow upcase because otherwise all you are doing is aliasing in long hand.

I am geting the same for reverse NoMethodError: undefined method reverse' for 0:Fixnum`

I agree it should return a Rational not nil especially since this is meant to emulate the ** operator.

I did the same thing although there is no need to switch back to int 0.0 == 0 => true

Am I the only one that used parallel assignment for this?

I agree since I have seen solutions using an inclusive range which according to the Kata is incorrect. Seems strange that it is a spec but is untested.

When I try to submit I keep getting "Failed to construct test fixture properly. Did you provide test cases?" Any idea why this is happening?

For Some reason this also occurs when I add Test.assert_equals(solution("MCMXC"),1990) to my tests.
All other tests work fine but as soon as I add this test I get the same error.

My solution seems to work for all of my tests and I would really like to submit it as I love seeing other peoples solutions but I don't want to forfeit which is currently my only option.

Please resolve this.