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[Kotlin] How to mock time ?

with kotest​

If you want to mock LocalDateTime:

val currentTime = LocalDateTime.now()

withConstantNow(currentTime) {
  LocalDateTime.now() shouldBe currentTime
  delay(10) // Code is taking a small amount of time to execute, but `now` changed!
  LocalDateTime.now() shouldBe currentTime
}

If you want to mock Instant: 

val currentTime = Instant.now()

withConstantNow(currentTime) {
  Instant.now() shouldBe currentTime
  delay(10) // Code is taking a small amount of time to execute, but `now` changed!
  Instant.now() shouldBe currentTime
}

Reference​