How to avoid Faker('domain_name') having the same domain twice in a row ?

I use factory.Faker(“domain_name”) in my factory, is there any way to stop it coming up with the same domain twice ?

I got a unique key error after calling my factory twice:

class SiteFactory(factory.DjangoModelFactory):
    class Meta:
        model = Site

    name = factory.Faker('word')
    domain = factory.Faker('domain_name')

        self.slovak_site = SiteFactory(id=5)
        self.czech_site = SiteFactory(id=6)

Got this unique key error one test run: DETAIL: Key (domain)=(smith.info) already exists.

[francoisfreitag]

Do you mean something like MyFactory.create_batch(2, domain=["example.org", "example.com"])? If so, then no, that is not possible.

What I meant by using factory.Sequence was:

class MyFactory(factory.DjangoModelFactory):
    class Meta:
        model = AModel

    domain = factory.Sequence(lambda n: f"www{n}.example.org")

That yields unique values for domain as long as the sequence is not reset. That does not make domain names as realistic as Faker’s, but they should be good enough for tests and are sure to be unique.

---

An overkill way to generate unique domain from Faker().domain_name():

from faker import Faker


def generate_domain_name(n):
    """
    Returns a Faker generated domain with the sequence number
    appended to the first part of the domain.

    With n=6, jim.org becomes jim6.com.
    """
    base_domain = Faker().domain_name()
    parts = base_domain.split(".")
    first_part = parts[0]
    parts = [f"{first_part}{n}", *parts[1:]]
    return ".".join(parts)


class MyFactory(factory.DjangoModelFactory):
    class Meta:
        model = AModel

    domain = factory.Sequence(generate_domain_name)

[stuaxo]

In the end I made a SiteFactory that handles this, posted below

It does feel like both faker and factoryboy would benefit from being able to handle uniqueness, especially when it comes to fields that are declared unique.

# some code ommited
class SiteFactory(factory.DjangoModelFactory):
    class Meta:
        model = Site

    name = factory.Faker('word')
    domain = factory.Faker('domain_name')

    _used_domains = set()

    @classmethod
    def _get_unique_domain(cls):
        domain = cls.domain.generate()
        for i in range(8):
            if domain not in cls._used_domains:
                break
            domain = cls.domain.generate()
        return domain

    @receiver(post_delete, sender=Site)
    def _remove_domain_from_cache(sender, instance, created, **kwargs):
        SiteFactory._used_domains.discard(instance.domain)

    @classmethod
    def _create(cls, model_class, *args, **kwargs):
        if "domain" not in kwargs:
            kwargs["domain"] = cls._get_unique_domain()
        cls._used_domains.add(kwargs["domain"])

        return super()._create(model_class, *args, **kwargs)