Reset an Lazy-field in Kotlin

ResetLazy.kt

# What is this? 
# Well..
# Sometimes you want to reset an val from a test where lazy props are being used. 
# This helps you do just that. 
# Amazing 🤩

# define the resetter 👇

import java.util.concurrent.atomic.AtomicReference
import kotlin.reflect.KProperty

fun <T> lazyWithReset(initializer: () -> T): ResetLazy<T> = ResetLazy(initializer)

class ResetLazy<T>(private val initializer: () -> T) {
  private val lazy: AtomicReference<Lazy<T>> = AtomicReference(lazy(initializer))
  operator fun getValue(ref: Any?, property: KProperty<*>): T = lazy.get().getValue(ref, property)
  fun reset(): Unit = lazy.set(lazy(initializer))
}

// usage 👇

val environmentLazyHandler: RestLazy<String> = lazyWithReset { someSlowMethodToLocateEnvironment() }
val environment: String by environmentLazyHandler

// usage in e.g tests 👇

internal fun onEnvironment(environment: String, f: () -> Unit) {
  environmentLazyHandler.reset()
  val existingEnvironment = System.getProperty("somePropertyThatIsUsedInsomeSlowMethodToLocateEnvironment")
  System.setProperty("somePropertyThatIsUsedInsomeSlowMethodToLocateEnvironment", environment)
  f()
  environmentLazyHandler.reset()
  existingEnvironment
    ?.let { System.setProperty("somePropertyThatIsUsedInsomeSlowMethodToLocateEnvironment", existingEnvironment) } 
    ?: System.clearProperty("somePropertyThatIsUsedInsomeSlowMethodToLocateEnvironment")
}

// usage in e.g tests 👇

@Test
fun `some test that requires environment a`() {
  onEnvironment("env-a") {
    somethingThatRequiresEnvironmentToBeReset()
  }
}

@Test
fun `some test that requires environment b`() {
  onEnvironment("env-b") {
    somethingThatRequiresEnvironmentToBeReset()
  }
}