Test thread execution in Java

class InstantExecutorExtension : BeforeEachCallback, AfterEachCallback {
    override fun beforeEach(context: ExtensionContext?) {
        ArchTaskExecutor.getInstance()
            .setDelegate(object : TaskExecutor() {
                override fun executeOnDiskIO(runnable: Runnable) = runnable.run()

                override fun postToMainThread(runnable: Runnable) = runnable.run()

                override fun isMainThread(): Boolean = true
            })
    }

    override fun afterEach(context: ExtensionContext?) {
        ArchTaskExecutor.getInstance().setDelegate(null)
    }
}

class RxTestSchedulersExtension: BeforeAllCallback {
    override fun beforeAll(context: ExtensionContext?) {
        RxAndroidPlugins.setInitMainThreadSchedulerHandler { Schedulers.trampoline() }
        RxJavaPlugins.setIoSchedulerHandler{ Schedulers.trampoline() }
        RxJavaPlugins.setNewThreadSchedulerHandler{ Schedulers.trampoline() }
        RxJavaPlugins.setSingleSchedulerHandler { Schedulers.trampoline() }
    }
}