Continually

As the dual of eventually, continually allows you to assert that a block of code succeeds, and continues to succeed, for a period of time. For example you may want to check that a http connection is kept alive for 60 seconds after the last packet has been received. You could sleep for 60 seconds, and then check, but if the connection was terminated after 5 seconds, your test will sit idle for a further 55 seconds before then failing. Better to fail fast.

class MyTests : ShouldSpec() {
  init {
    should("pass for 60 seconds") {
      continually(60.seconds) {
        // code here that should succeed and continue to succeed for 60 seconds
      }
    }
  }
}

By default, the function passed to the continually block is executed every 25 milliseconds. We can explicitly set the poll interval. In the following example we set it to 50 milliseconds:

class MyTests: ShouldSpec() {
  init {
    should("pass for 60 seconds") {

     val config = continuallyConfig<Unit> {
        duration = 60.seconds
        interval = 50.milliseconds
     }

      continually(config) {
        // code here that should succeed and continue to succeed for 60 seconds
      }
    }
  }
}

Listeners

If we need to record successful executions of the block(), we can use a listener, as shown in the following example:

var invoked = 0
val executed = mutableMapOf<Int, Int>()
val config = continuallyConfig<Int> {
  duration = 500.milliseconds
  listener = { index, value -> executed[index] = value }
}
val result = testContinually(config) {
  invoked*2 shouldBe 2*invoked
  invoked++ + 42
}
assertSoftly {
  executed.keys.shouldHaveSize(20)
  executed.forEach { (k, v) ->
     v shouldBe k + 42
  }
}