@Override
    public Flux<FavouriteProduct> findFavouriteProducts(String userId) {
        return this.favouriteProductRepository.findAllByUserId(userId);
    }
@Test
    void findFavouriteProducts_ReturnsFavouriteProducts() {
        // given
        doReturn(Flux.fromIterable(List.of(
                new FavouriteProduct(UUID.fromString("fe87eef6-cbd7-11ee-aeb6-275dac91de02"), 1,
                        "5f1d5cf8-cbd6-11ee-9579-cf24d050b47c"),
                new FavouriteProduct(UUID.fromString("23ff1d58-cbd8-11ee-9f4f-ef497a4e4799"), 3,
                        "5f1d5cf8-cbd6-11ee-9579-cf24d050b47c")
        ))).when(this.favouriteProductRepository).findAllByUserId("5f1d5cf8-cbd6-11ee-9579-cf24d050b47c");

        // when
        StepVerifier.create(this.service.findFavouriteProducts("5f1d5cf8-cbd6-11ee-9579-cf24d050b47c"))
                // then
                .expectNext(
                        new FavouriteProduct(UUID.fromString("fe87eef6-cbd7-11ee-aeb6-275dac91de02"), 1,
                                "5f1d5cf8-cbd6-11ee-9579-cf24d050b47c"),
                        new FavouriteProduct(UUID.fromString("23ff1d58-cbd8-11ee-9f4f-ef497a4e4799"), 3,
                                "5f1d5cf8-cbd6-11ee-9579-cf24d050b47c")
                )
                .verifyComplete();
    }