Off by a microsecond

[life4u2c]

Perhaps not the worst thing in the world, but when I updated to 0.1.3, I found I was off by a single microsecond in my test.

I was doing something like
with fake_time('1970-01-01 00:00:07.012')
and in my test, datetime.now() would end up returning a time that represented 1970-01-01 00:00:07.011999

And later, I am testing a certain time has elapsed, but I would have to account for this single microsecond to be off. I am also plugged in with the latest of these dependencies

pytest-cov==5.0.0
pytest-env==1.1.3
pytest-libfaketime==0.1.2
pytest-mock==3.14.0
pytest==8.2.1
pytest-xdist[psutil]==3.6.1

These are not all inclusive of everything in my setup, but hopefully of is enough to help identify any issues. Running in a docker environment with the docker container python:3.8.6 and setting up these environment variables within my Dockerfile

ENV LD_LIBRARY_PATH="/usr/local/lib/python3.8/site-packages/libfaketime/vendor/libfaketime/src"
ENV LD_PRELOAD="libfaketime.so.1"
ENV DONT_FAKE_MONOTONIC="1"
ENV FAKETIME_DID_REEXEC=true
ENV FAKETIME_NO_CACHE="1"

A clue maybe: There may be some pytest-xdist conflict issue. Not everyone on my team was seeing this same problem, and we did not have pytest-xdist pinned to a version, so we may have been on different versions. Trying to put everything to the latest version, available today, and I see this issue with the time being off by 1 microsecond.

[life4u2c]

Sorry, I may need to provide more clarification.

The problem exists on both 0.1.2 and 0.1.3, but I don't know that it's a problem with this library, and so not sure where to put this issue. It may be some sort of issue with a certain combination of dependencies. I am not sure. I was updating dependencies to resolve another unrelated issue with our setup. And ran into this issue.

[life4u2c]

I was talking to someone about this, seems other teams in my org have also run into interesting issues. I thought I would provide info on that initial issue, that had me looking at upgrading. With pytest.xdist[psutil] not pinned in our original setup, Some people were experiencing passing tests, and others, who pulled a more recent version were failing tests.

Example:

with fake_time("2018-4-09 19:00:00") as frozen_datetime:
    ...
    frozen_datetime.tick()
    ...

Any of our tests which were incrementing the time with a call to tick() were not experiencing the time move forward. This was our requirements setup that looked like:

pytest-cov==5.0.0
pytest-env==1.1.3
pytest-libfaketime==0.1.2
pytest-mock==3.14.0
pytest==8.1.1
pytest-xdist[psutil]