What is a fixture?¶
A fixture is a collection of files that contain the serialized contents of the database. Each fixture has a unique name, and the files that comprise the fixture can be distributed over multiple directories, in multiple applications.
How to produce a fixture?¶
How to use a fixture?¶
Fixtures can be used to pre-populate database with data for tests:
class MyTestCase(TestCase): fixtures = ["fixture-label"]
django-admin loaddata <fixture label>
Where Django looks for fixtures?¶
Django will search in these locations for fixtures:
- In the
fixturesdirectory of every installed application
- In any directory listed in the
- In the literal path named by the fixture
Django will load any and all fixtures it finds in these locations that match the provided fixture names. If the named fixture has a file extension, only fixtures of that type will be loaded. For example:
django-admin loaddata mydata.json
would only load JSON fixtures called
mydata. The fixture extension must
correspond to the registered name of a
If you omit the extensions, Django will search all available fixture types for a matching fixture. For example:
django-admin loaddata mydata
would look for any fixture of any fixture type called
mydata. If a fixture
mydata.json, that fixture would be loaded as a JSON
The fixtures that are named can include directory components. These directories will be included in the search path. For example:
django-admin loaddata foo/bar/mydata.json
<app_label>/fixtures/foo/bar/mydata.json for each installed
<dirname>/foo/bar/mydata.json for each directory in
FIXTURE_DIRS, and the literal path
Fixtures loading order¶
Multiple fixtures can be specified in the same invocation. For example:
django-admin loaddata mammals birds insects
or in a test case class:
class AnimalTestCase(TestCase): fixtures = ["mammals", "birds", "insects"]
The order in which fixtures are loaded follows the order in which they are listed, whether it’s when using the management command or when listing them in the test case class as shown above.
In these examples, all the fixtures named
mammals from all applications (in
the order in which applications are defined in
be loaded first. Subsequently, all the
birds fixtures will be loaded,
followed by all the
Be aware that if the database backend supports row-level constraints, these constraints will be checked at the end of the transaction. Any relationships across fixtures may result in a load error if the database configuration does not support deferred constraint checking (refer to the MySQL docs for an example).
How fixtures are saved to the database?¶
When fixture files are processed, the data is saved to the database as is.
save() methods are not called, and
post_save signals will be called with
raw=True since the instance only contains attributes that are local to the
model. You may, for example, want to disable handlers that access
related fields that aren’t present during fixture loading and would otherwise
raise an exception:
from django.db.models.signals import post_save from .models import MyModel def my_handler(**kwargs): # disable the handler during fixture loading if kwargs["raw"]: return ... post_save.connect(my_handler, sender=MyModel)
You could also write a decorator to encapsulate this logic:
from functools import wraps def disable_for_loaddata(signal_handler): """ Decorator that turns off signal handlers when loading fixture data. """ @wraps(signal_handler) def wrapper(*args, **kwargs): if kwargs["raw"]: return signal_handler(*args, **kwargs) return wrapper @disable_for_loaddata def my_handler(**kwargs): ...
Just be aware that this logic will disable the signals whenever fixtures are
deserialized, not just during
Fixtures may be compressed in
format. For example:
django-admin loaddata mydata.json
would look for any of
mydata.json.xz. The first
file contained within a compressed archive is used.
Note that if two fixtures with the same name but different fixture type are
discovered (for example, if
mydata.xml.gz were found in
the same fixture directory), fixture installation will be aborted, and any data
installed in the call to
loaddata will be removed from the database.
MySQL with MyISAM and fixtures
The MyISAM storage engine of MySQL doesn’t support transactions or constraints, so if you use MyISAM, you won’t get validation of fixture data, or a rollback if multiple transaction files are found.
If you’re in a multi-database setup, you might have fixture data that you want to load onto one database, but not onto another. In this situation, you can add a database identifier into the names of your fixtures.
For example, if your
DATABASES setting has a
defined, name the fixture
mydata.users.json.gz and the fixture will only be loaded when you
specify you want to load data into the