Eli Fidler 760ea4316c avoid signed-integer underflow, which is undefined behavior
maybe these tests should just be deleted?

UBSAN gave:
runtime error: signed integer overflow: -9223372036854775808 - 1 cannot be represented in type 'long'
runtime error: signed integer overflow: -9223372036854775808 - 2 cannot be represented in type 'long'
2016-06-14 07:01:41 -07:00
..