Rails `travel_to` changes the value of `usec` to 0

https://github.com/rails/rails/blob/4dcc5435e9569e084f6f90fcea6e7c37d7bd2b4d/activesupport/lib/active_support/testing/time_helpers.rb#L145

In and of itself, not a huge deal. However, when you combine it with the way that active record quotes times:

https://github.com/rails/rails/blob/4dcc5435e9569e084f6f90fcea6e7c37d7bd2b4d/activesupport/lib/active_support/testing/time_helpers.rb#L145

It can lead to some incredibly subtle bugs in your tests that use queries in their assertions. Long story short, if your query relies on a time comparison, you may not return anything. :|