Model Mommy: Smart fixtures for better tests
Model-mommy offers you a smart way to create fixtures for testing in Django. With a simple and powerful API you can create many objects with a single line of code.
pip install model_mommy
Let's say you have an app family with a model like this:
class Kid(models.Model): happy = models.BooleanField() name = models.CharField(max_length=30) age = models.IntegerField() bio = models.TextField() wanted_games_qtd = models.BigIntegerField() birthday = models.DateField() appointment = models.DateTimeField()
To create a persisted instance, just call Mommy:
from model_mommy import mommy from family.models import Kid kid = mommy.make(Kid)
No need to pass attributes every damn time.
Importing every model over and over again is boring. So let Mommy import them for you:
from model_mommy import mommy # 1st form: app_label.model_name kid = mommy.make('family.Kid') # 2nd form: model_name dog = mommy.make('Dog')
|||You can only use the 2nd form on unique model names. If you have an app family with a Dog, and an app farm with a Dog, you must use the app_label.model_name form.|
|||model_name is case insensitive.|
Mommy also handles relationships. Say the kid has a dog:
class Dog(models.Model): owner = models.ForeignKey('Kid')
when you ask Mommy:
from model_mommy import mommy rex = mommy.make('family.Dog')
She will also create the Kid, automagically.
Defining some attributes
Of course it's possible to explicitly set values for attributes.
from model_mommy import mommy another_kid = mommy.make('family.Kid', age=3)
Related objects attributes are also reachable:
from model_mommy import mommy bobs_dog = mommy.make('family.Dog', owner__name='Bob')
Non persistent objects
If don't need a persisted object, Mommy can handle this for you as well:
from model_mommy import mommy kid = mommy.prepare('family.Kid')
It works like make, but it doesn't persist the instance.
More than one instance
If you need to create more than one instance of the model, you can use the _quantity parameter for it:
from model_mommy import mommy kids = mommy.make('family.Kid', _quantity=3) assert len(kids) == 3
It also works with prepare:
from model_mommy import mommy kids = mommy.prepare('family.Kid', _quantity=3) assert len(kids) == 3
How mommy behaves?
By default, model-mommy skips fields with null=True or blank=True. Also if a field has a default value, it will be used.
You can override this behavior by explicitly defining values.
When shouldn't you let mommy generate things for you?
If you have fields with special validation, you should set their values by yourself.
Model-mommy should handle fields that:
- don't matter for the test you're writing;
- don't require special validation (like unique, etc);
- are required to create the object.
Currently supported fields
- BooleanField, IntegerField, BigIntegerField, SmallIntegerField, PositiveIntegerField, PositiveSmallIntegerField, FloatField, DecimalField
- CharField, TextField, SlugField, URLField, EmailField
- ForeignKey, OneToOneField, ManyToManyField
- DateField, DateTimeField, TimeField
- FileField, ImageField
If you're not confortable with random data, or you have some custom fields, or even you just want to improve the semantics of the generated data, there's hope for you.
You can define a recipe, which is a set of rules to generate data for your models. Create a module called mommy_recipes.py at your app's root directory:
from model_mommy.recipe import Recipe from family.models import Person person = Recipe(Person, name = 'John Doe', nickname = 'joe', age = 18, birthday = date.today(), appointment = datetime.now() )
Note you don't have to declare all the fields if you don't want to. Omitted fields will be generated automatically.
The variable person serves as the recipe name:
from model_mommy import mommy mommy.make_recipe('family.person')
Or if you don't want a persisted instance:
from model_mommy import mommy mommy.prepare_recipe('family.person')
You can use the _quantity parameter as well if you want to create more than one object from a single recipe.
Recipes with foreign keys
You can define foreign_key relations:
from model_mommy import mommy from model_mommy.recipe import Recipe, foreign_key from family.models import Person, Dog person = Recipe(Person, name = 'John Doe', nickname = 'joe', age = 18, birthday = date.today(), appointment = datetime.now() ) dog = Recipe(Dog, breed = 'Pug', owner = foreign_key(person) )
Notice that person is a recipe.
You may be thinking: "I can put the Person model instance directly in the owner field". That's not recommended.
Using the foreign_key is important for 2 reasons:
- Semantics. You'll know that attribute is a foreign key when you're reading;
- The associated instance will be created only when you call make_recipe and not during recipe definition;
Recipes with callables
It's possible to use callables as recipe's attribute value.
from datetime import date from model_mommy.recipe import Recipe from family.models import Person person = Recipe(Person, birthday = date.today, )
When you call make_recipe, Mommy will set the attribute to the value returned by the callable.
Sequences in recipes
Sometimes, you have a field with an unique value and using make can cause random errors. Also, passing an attribute value just to avoid uniqueness validation problems can be tedious. To solve this you can define a sequence with seq
from model_mommy.recipe import Recipe, seq from family.models import Person person = Recipe(Person, name = seq('Joe'), age = seq(15) ) p = mommy.make_recipe('myapp.person') p.name >>> 'Joe1' p.age >>> 16 p = mommy.make_recipe('myapp.person') p.name >>> 'Joe2' p.age >>> 17
This will append a counter to strings to avoid uniqueness problems and it will sum the counter with numerical values.
Overriding recipe definitions
Passing values when calling make_recipe or prepare_recipe will override the recipe rule.
from model_mommy import mommy mommy.make_recipe('model_mommy.person', name='Peter Parker')
This is useful when you have to create multiple objects and you have some unique field, for instance.
Because of the changes of model_mommy's API, the following methods are deprecated and will be removed in one of the future releases:
- mommy.make_one -> should use the method mommy.make instead
- mommy.prepare_one -> should use the method mommy.prepare instead
- mommy.make_many -> should use the method mommy.make with the _quantity parameter instead
- mommy.make_many_from_recipe -> should use the method mommy.make_recipe with the _quantity parameter instead
- Prepare a virtual environment.
pip install virtualenvwrapper mkvirtualenv --no-site-packages --distribute
- Install the requirements.
pip install -r requirements.txt
- Run the tests.
Model-mommy was inspired by many great open source software like ruby's ObjectDaddy and FactoryGirl.
Doubts? Loved it? Hated it? Suggestions?
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