Calculate travel_offset to align with the precision of argument to Timecop.travel

travisjeffery / timecop

A gem providing "time travel", "time freezing", and "time acceleration" capabilities, making it simple to test time-dependent code. It provides a unified method to mock Time.now, Date.today, and DateTime.now in a single call.

MIT License

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Calculate travel_offset to align with the precision of argument to Timecop.travel #421

Closed dgholz closed 3 weeks ago

dgholz commented 3 months ago

Subtracting two Times returns a Float, which may not be accurate down to subsecond resolution. Because Floats are stored as double-precision values (IEEE 754), they can have resolutions much higher than the typical minimum clock precision of 10e-9 seconds. Which can result in two Time object not comparing as equal when they are the same down to the nanosecond, when one has had a travel_offset applied to it.

To fix #420.

dgholz commented 2 months ago

@joshuacronemeyer I'd greatly appreciate your opinion on this PR, if you have the time.

dgholz commented 3 weeks ago

@joshuacronemeyer I still think this change has a significant benefit to users & would appreciate your opinions on it

joshuacronemeyer commented 3 weeks ago

@dgholz thank you for your detailed issue and for this PR. I was spaced out i guess when this came in, so thanks for bringing it to my attention. I will try to look at this soon.

joshuacronemeyer commented 3 weeks ago

Looks good!

joshuacronemeyer commented 3 weeks ago

@dgholz I reverted this because of a failing test.

  1) Failure:
TestTimeStackItem#test_travel_offset_aligns_to_travel_time [test/time_stack_item_test.rb:314]:
travel offset precision (4503599627370496000000000) does not align with travel time precision (900719925474099200000000).
Expected: 0
  Actual: 900719925474099200000000

Happy to look at it again.