How to create a Factory-Boy factory for a model with TaggableManager field

Question

How can I create a field in Factory-Boy to TaggableManager from django-taggit?

The following does not work:

First:

class ExperimentFactory(factory.DjangoModelFactory):
    class Meta:
        model = Experiment
        django_get_or_create = ('owner', 'name', 'start_date', 'stop_date', )

    owner = factory.SubFactory(UserFactory)
    name = factory.Sequence(lambda n : 'Experiment %s' % n)

    start_date = fuzzy.FuzzyDate(start_date=datetime.date(2003, 2, 1), 
                                     end_date = datetime.date.today() + timedelta(days=4*52*7+5))

    tags = [u'abc, cde', u'xzy']

The error is: TypeError: 'tags' is an invalid keyword argument for this function

Second: (with factory.post_generation). So Instead of the last line there is

@factory.post_generation
def post_tags(self, create, extracted, **kwargs):
    self.tags = [u'abc, cde', u'xzy']
    # self.save() # This does not have any effects

I get as result by Experiment.objects.get(pk=1).tags is []

For some details:

The testing of the objects in a TestCase is:

experiment = ExperimentFactory(owner = self.user)
saved_experiment = Experiment.objects.get(name=experiment.name) 

self.assertEquals(len(experiment.tags), len(saved_experiment.tags.all())) # AssertError: 2 != 0
self.assertItemsEqual(experiment.tags, saved_experiment.tags.all())

The odd thing is that in self.experiments the tags are set. The post_tags() method is called.

The model is:

class Experiment(models.Model):
     owner = models.ForeignKey(User, related_name='experiments') 

     name = models.CharField(max_length=32, default='')
     start_date = models.DateField()

     tags = TaggableManager()

Answer 1

finally found the solution:

@factory.post_generation
def post_tags(self, create, extracted, **kwargs):
    self.tags.add(u'abc, cde', u'xzy')

Answer 2

For anyone else coming here who wants a more generalised example of using Factory Boy and django-taggit, the Factory Boy docs include a Many-to-Many example which is useful. So:

import factory

from myapp.models import Experiment


class ExperimentFactory(factory.DjangoModelFactory):
    class Meta:
        model = Experiment

    # other fields here

    @factory.post_generation
    def tags(self, create, extracted, **kwargs):
        if not create:
            # Simple build, do nothing.
            return

        if extracted:
            # A list of tags were passed in, use them.
            for tag in extracted:
                self.tags.add(tag)

Then you can do:

from myapp.factories import ExperimentFactory

ExperimentFactory(name='A Name', tags=['Tag 1', 'Tag 2', 'Another tag',])

Note, this won't create tags if you do ExperimentFactory.build(), only if you do ExperimentFactory.create() or its synonym ExperimentFactory().