@Test
void purchasingNoItems() {

    final Zonky zonky = harmlessZonky();
    final PowerTenant tenant = mockTenant(zonky);
    final PurchasingOperationDescriptor d = mockPurchasingOperationDescriptor();
    final StrategyExecutor<ParticipationDescriptor, PurchaseStrategy, Participation> exec = new StrategyExecutor<>(
            tenant, d);
    when(tenant.getPurchaseStrategy()).thenReturn(Optional.of(ALL_ACCEPTING_PURCHASE_STRATEGY));
    assertThat(exec.get()).isEmpty();
    final List<Event> e = getEventsRequested();
    assertThat(e).isEmpty();
}