Prior to this commit, the tests would fail because microseconds would exceed a[1] for no good reason [2]. This
limit of 999999 for some reason once in a while [1]. Failing the tests for no
good reason...
This fixes it.
[1] https://jenkins.softwareheritage.org/job/DSTO/job/tests/1264/console
[2] microseconds would exceed a limit of 999999 from time to time