add a test which identifies a broken algorithm

[philihp]

I believe your implementation does not work. Here is a test which identifies this.

     AssertionError: all of original elements should be included in output: expected
[ 'A', 'B', 'B', 'A', 'A', 'A', 'A' ] to be a superset of
[ 'A', 'B', 'C', 'D', 'E', 'F', 'G' ]

[SkepticalHippo]

Thanks for bringing this up. I'll look into it.

[SkepticalHippo]

Should be fixed in b4c2ca2