Exercise: Coroutine time measurement
In order to measure a block execution time, you defined the following function, that can measure real time on production, and virtual time in unit tests:
suspend fun measureCoroutine(
body: suspend () -> Unit
): Duration {
val dispatcher = coroutineContext[ContinuationInterceptor]
return if (dispatcher is TestDispatcher) {
val before = dispatcher.scheduler.currentTime
body()
val after = dispatcher.scheduler.currentTime
after - before
} else {
measureTimeMillis {
body()
}
}.milliseconds
}
However, you found that it is not very convenient to use because it lacks a contract. Define a contract to make the following code compile:
runTest {
val result: String
val duration = measureCoroutine {
delay(1000)
result = "OK"
}
println(duration) // 1000 ms
println(result) // OK
}
runBlocking {
val result: String
val duration = measureCoroutine {
delay(1000)
result = "OK"
}
println(duration) // 1000 ms
println(result) // OK
}
This problem can either be solved in the below playground or you can clone kotlin-exercises project and solve it locally. In the project, you can find code template for this exercise in advanced/contract/MesureCoroutineTime.kt. You can find there starting code and example usage.
Once you are done with the exercise, you can check your solution here.
Playground
import kotlinx.coroutines.ExperimentalCoroutinesApi
import kotlinx.coroutines.delay
import kotlinx.coroutines.runBlocking
import kotlinx.coroutines.test.TestDispatcher
import kotlinx.coroutines.test.runTest
import kotlin.contracts.ExperimentalContracts
import kotlin.contracts.InvocationKind
import kotlin.contracts.contract
import kotlin.coroutines.ContinuationInterceptor
import kotlin.coroutines.coroutineContext
import kotlin.system.measureTimeMillis
import kotlin.time.Duration
import kotlin.time.Duration.Companion.milliseconds
suspend fun measureCoroutine(
body: suspend () -> Unit
): Duration {
val dispatcher = coroutineContext[ContinuationInterceptor]
return if (dispatcher is TestDispatcher) {
val before = dispatcher.scheduler.currentTime
body()
val after = dispatcher.scheduler.currentTime
after - before
} else {
measureTimeMillis {
body()
}
}.milliseconds
}
suspend fun main() {
runTest {
val result: String
val duration = measureCoroutine {
delay(1000)
result = "OK"
}
println(duration) // 1000 ms
println(result) // OK
}
runBlocking {
val result: String
val duration = measureCoroutine {
delay(1000)
result = "OK"
}
println(duration) // 1000 ms
println(result) // OK
}
}
