Bg/two word permutation

When getting the permutations for the two words `Hello World ` substituting spaces with `-` s (with a space at the end), I believe the expected output should include `Hello World-`, but not include `Hello World` (without a space at the end).

Here is a spec that demonstrates when Darryl Jenks does not create the expected permutation. If I'm in error, please let me know and I will approach it differently.