Uninstall fixture

[jordanb]

This feature adds the capability to uninstall fixtures using one or a set of fixture keys.

We know that the FixturesManager class has a save_instance method and several install_fixture related methods. In a similar way and for parity sake we add a delete_instance as well as several uninstall_fixture methods.

Why is that useful?

This is how things were before:

class TestToaster(unittest.TestCase, charlatan.FixturesManagerMixin):

    def setUp(self):
        self.install_fixture('toast') # this feels magical

    def tearDown(self):
        toast_fixture = self.get_fixture('toast')
        toast = Toast.get(Toast.id == toast_fixture.id)
        self.session.delete(toast)
        self.session.commit() # why not the same magical pattern?

And now you'll be able to do:

class TestToaster(unittest.TestCase, charlatan.FixturesManagerMixin):

    def setUp(self):
        self.install_fixture('toast') # this feels magical

    def tearDown(self):
        self.uninstall_fixture('toast') # this also feels magical

How the magic works?

When calling FixturesManager.delete_instance, the logic expects (and hopes) that your model instance will have a Model.delete_instance() method or a Model.delete() method. If it has both, only Model.delete_instance will be called. This works for peewee and other standard orm. It is very similar to how the FixturesManager.save_instance method relies on the Model.save() method being defined by your orm.

Limitations

• deleting is trivial and not recursive (not even an option because too orm-specific)
• make sure your fixtures are set in a additive order in terms of relationships: objects with dependencies set after in the yaml, in an additive manner

[coveralls]

Coverage remained the same when pulling 4b28afaad5d858f4c7b5da72ded6ef6add52bc09 on uninstall_fixture into 145707fbb4bdc3e7e0a90cf188f49b954bc9a4a3 on master.

[charlax]

I'm still uncomfortable with this, as it is too framework specific... What do you think of using this: http://peewee.readthedocs.org/en/latest/peewee/playhouse.html#test-utils

[charlax]

Will still think through this though.

[jordanb]

Thank you for your feedback. This feature was not meant to support peewee only. It does have assumptions about the framework but:

1. it is not more or less framework specific than relying on the existence of a save method on the models, like charlatan does currently
2. most ORMs rely on a delete_instance or delete method
3. anyway, it provides hooks in order to customize the needs for ORMs that are not relying on these methods to delete instances (a before_delete hook was indeed added)
4. charlatan is already very tightly coupled to SQLAlchemy, maybe some refactoring with adapters is necessary in that case to be totally ORM agnostic and not rely on the existence of any methods

@charlax Let me know what you think.

[charlax]

Looking great, left a few comments. Making it totally ORM agnostic would be great but probably out of scope.

Can you add some more tests and a bit more documentation?

Thanks a lot Jordan!

[coveralls]

Coverage remained the same when pulling e23aa4ed0ffaa1681ca070a554bed9079938ab13 on uninstall_fixture into 145707fbb4bdc3e7e0a90cf188f49b954bc9a4a3 on master.