Slight edit might be required from the Instruction page:

This line:

If there aren't enough spare chairs available, return

Should be updated to:

If there aren't enough spare chairs available, return 'Not enough!'

i.e. missing the 'Not enough!'

Great Kata series!
Not sure if it's just me, the hyperlinks to the other challenges in the series doesn't seem to work. e.g.

The Office I - Outed
The Office II - Boredeom Score
The Office III - Broken Photocopier
The Office IV - Find a Meeting Room
The Office V - Find a Chair

More than happy to fix this myself (if it is indeed an actual bug and not just me) - not sure how to do the edit though. Any tips?

When I changed the test case to like this the code fails?

var arr = [10, 12, 10, 8, 12, 7, 6, 4, 10, 12];
Test.assertSimilar( highestRank(arr), 12);