Ktor engine reuse for tests

KtorTests.kt

import io.ktor.config.*
import io.ktor.server.engine.*
import io.ktor.server.testing.*
import org.junit.jupiter.api.extension.*
import org.slf4j.LoggerFactory

class KtorTests(private val app: App) : AfterAllCallback, BeforeAllCallback {

    val env = applicationEngineEnvironment {
        config = MapApplicationConfig("ktor.deployment.environment" to "test")
        log = LoggerFactory.getLogger("ktor.test")
    }

    val engine by lazy {
        val engine = TestApplicationEngine(env) {}
        engine.start()
        engine
    }

    fun test(block: TestApplicationEngine.() -> Unit) {
        with(engine) { block() }
    }

    override fun beforeAll(context: ExtensionContext?) {
        with(engine) {
            with(app) { application.mainModule() }
        }
    }

    override fun afterAll(context: ExtensionContext?) {
        engine.stop(0, 0)
    }
}