unittests: Ensure too short patterns are correctly rejected

3 jobs for master in 24 minutes and 58 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #418795
amd64 docker
asan-ubsan

00:24:57

passed #418791
amd64 docker
coverage

00:04:26

87.2%
passed #418798
amd64 docker
tsan

00:16:08