Characterisation test of Caffeine refreshable cache

CaffeineRefreshableCacheTest.kt

import com.github.benmanes.caffeine.cache.CacheLoader
import com.github.benmanes.caffeine.cache.Caffeine
import com.github.benmanes.caffeine.cache.Ticker
import org.assertj.core.api.Assertions.assertThat
import org.junit.Test
import java.util.concurrent.TimeUnit
import java.util.concurrent.atomic.AtomicInteger

class CaffeineAsyncRefreshableCacheTest {
    @Test
    fun `refreshable cache works as expected`() {
        val loader = SpyingCacheLoader({ "one" }, { "uno" }, { throw IllegalArgumentException() })
        val ticker = AdjustableTicker(0)

        val cache = Caffeine.newBuilder()
            .refreshAfterWrite(1, TimeUnit.NANOSECONDS)
            .maximumSize(100)
            .ticker(ticker)
            .build(loader)

        assertThat(cache.get("1")).isEqualTo("one")

        ticker.reference = 10

        assertThat(cache.get("1")).isIn("one", "uno")

        ticker.reference = 20

        assertThat(cache.get("1")).isEqualTo("uno")

        ticker.reference = 30

        assertThat(cache.get("1")).isEqualTo("uno")

        ticker.reference = 40

        assertThat(cache.get("1")).isEqualTo("uno")
    }

    class SpyingCacheLoader(vararg val returnValues: () -> String) : CacheLoader<String, String> {
        val loads = AtomicInteger(0)

        override fun load(key: String): String? {
            val nthValue = loads.getAndUpdate { if (it < returnValues.size - 1) it.inc() else it }
            return returnValues[nthValue]()
        }
    }

    class AdjustableTicker(var reference: Long) : Ticker {
        override fun read(): Long = reference
    }
}