Note: You will have to handle multiple spaces, and leading/trailing spaces.

It's not explained how exactly should we handle them.

Ruby: input is mutable and used afterwards to produce reference and error message

Multiple or leading or trailing spaces are not tested in Python and Javascript.

The description never mentions reversing the position of spaces.

For

'You Know When  THAT  Hotline Bling'

if we only swap the case and reverse the order of words as the description asks, we should get:

'bLING hOTLINE that  wHEN  kNOW yOU'

However, in ruby, the test expects

'bLING hOTLINE  that  wHEN kNOW yOU'

Either the description should be clearer on how spaces are supposed to be repositioned, or the test cases need to be fixed.

Note: You will have to handle multiple spaces, and leading/trailing spaces.

the word 'handle' in this sentence is ambigious. I understood it to mean 'remove.'

I suggest replacing this sentence with something like:

Your solution should preserve the appearance of multiple spaces and/or leading/trailing spaces.