I have solved this Kata in C#.
I think the Kata description is poor/not clear. It should state clearly that error checking has to be implemented, and in case of multiple numbers with no operator in input string, the calculator should return the last number in the input string (not the first or second)?!

The problem i found is that my solution passed all sample tests, however when attempting the Kata i got two tests failing:

1. The 'Should parse numbers' test returned : Expected 3.0d +/-0d but was 1.0d +/-0d
2. The 'Should parse float numbers test returned : Expected 3.5d +/-0d but was 1.0d +/-0d

I could only find out that error checking has to be implemented in the way above by checking the questions section.
Please correct the description for the community.

Beautiful