2736c9e05 Avoid unintentional unsigned integer wraparounds in tests (practicalswift)
Pull request description:
Avoid unintentional unsigned integer wraparounds in tests.
This is a subset of #11535 as suggested by @MarcoFalke :-)
Tree-SHA512: 4f4ee8a08870101a3f7451aefa77ae06aaf44e3c3b2f7555faa2b8a8503f97f34e34dffcf65154278f15767dc9823955f52d1aa7b39930b390e57cdf2b65e0f3