'a' to 'c' ok
'a' until 'c' ok
'a' to 'b' ok
'a' until 'b' ok
'a' to 'a' ok
'a' until 'a' ok
'b' to 'a' ok
'b' until 'a' ok
'c' to 'a' ok
'c' until 'a' ok