getNewsletterSalesChannelIds example

    }

    public function getConfig(): RuleConfig
    {
        return (new RuleConfig())
            ->booleanField('isNewsletterRecipient');
    }

    private function matchIsNewsletterRecipient(CustomerEntity $customer, SalesChannelContext $context): bool
    {
        $salesChannelIds = $customer->getNewsletterSalesChannelIds();

        return \is_array($salesChannelIds) && \in_array($context->getSalesChannelId(), $salesChannelIds, true);
    }
}

// create unrelated newsletter recipient which should not be involved when updating the customer's newsletter sales channel ids         $this->createNewsletterRecipient($context, 'foobar@example.com', TestDefaults::SALES_CHANNEL);

        // subscribe to default sales channel and assert that array contains only that id         $newsletterRecipientA = $this->createNewsletterRecipient($context, $email, TestDefaults::SALES_CHANNEL);

        /** @var EntityRepository<CustomerCollection> $customerRepository */
        $customerRepository = $this->getContainer()->get('customer.repository');
        $customer = $customerRepository->search(new Criteria([$customerId]), $context)->getEntities()->first();
        static::assertNotNull($customer);

        static::assertNotNull($customer->getNewsletterSalesChannelIds());
        static::assertCount(1, $customer->getNewsletterSalesChannelIds());
        static::assertContains(TestDefaults::SALES_CHANNEL, $customer->getNewsletterSalesChannelIds());

        // subscribe to alternative sales channel and assert that array contains ids of both sales channels         $newsletterRecipientB = $this->createNewsletterRecipient($context, $email, $alternativeSalesChannel['id'], NewsletterSubscribeRoute::STATUS_DIRECT);

        $customer = $customerRepository->search(new Criteria([$customerId]), $context)->getEntities()->first();
        static::assertNotNull($customer);

        static::assertNotNull($customer->getNewsletterSalesChannelIds());
        static::assertCount(2, $customer->getNewsletterSalesChannelIds());