@Test(timeout = 30_000)
public void testExternalAction() {

    newReconciler(current -> Collections.emptyList());
    assertThat(reconciler.apply(c -> Mono.just("update")).block()).isEqualTo("update");
    assertThat(changesSubscriber.takeNext()).isEqualTo("update");
    assertThat(changesSubscriber.takeNext()).isNull();
}