public void setReactorNameSupplier(Supplier<String> reactorNameSupplier) {
        this.reactorNameSupplier = checkNotNull(reactorNameSupplier, "reactorNameSupplier");
    }
@Test
    public void test_setReactorNameSupplier_whenNull() {
        ReactorBuilder builder = newBuilder();
        assertThrows(NullPointerException.class, () -> builder.setReactorNameSupplier(null));
    }