I (think that I) want to write a test that asserts...

# kotlinx-datetime

[leandro]

I (think that I) want to write a test that asserts that a specific amount of Duration has passed, but unsure how to do it. Or, in different words: given an Instant, I would like to simulate running in the future. Do I need some kind of mutable Clock, or should I use timeMark?

[Javier]

https://github.com/Kotlin/kotlinx-datetime/issues/33

[Marc Knaup]

My back-end exclusively uses a Clock instance provided through dependency injection. During unit testing a custom simulated clock instance is provided.

[leandro]

@Marc Knaup do you advance/rewind the time in your tests? I also inject the Clock interface in my SUT, but I am unsure how to test it

[Marc Knaup]

Yeah, roughly like that:

[Marc Knaup]

Test code simply calls clock.advance() to simulate a different time. Optionally it can state how much time has passed.

[Marc Knaup]

Timestamp would be Instant for you I guess :)

[leandro]

Fantastic! It looks very similar to what I think I need

[Marc Knaup]

It’ll make a note to add a ManualClock to my fluid-time library 🙂

[Marc Knaup]

I’ve released fluid-time 0.12 with ManualClock for unit testing:
https://github.com/fluidsonic/fluid-time#readme