clock: Add test case for exactly negative sixty minutes.
clock: Add test case for exactly negative sixty minutes.

I encountered a solution that passed all provided test cases but would have failed this test.

jmluy/x-common,rpottsoh/x-common,jmluy/x-common,ErikSchierboom/x-common,ErikSchierboom/x-common,exercism/x-common,petertseng/x-common,exercism/x-common,petertseng/x-common,rpottsoh/x-common,jmluy/x-common