Generating fixture data with Python's fixture module

Question

I'm working with the fixture module for the first time, trying to get a better set of fixture data so I can make our functional tests more complete.

I'm finding the fixture module a bit clunky, and I'm hoping there's a better way to do what I'm doing. This is a Flask/SQLAlchemy app in Python 2.7, and we're using nose as a test runner.

So I have a set of employees. Employees have roles. There are a few pages with rather complex permissions, and I'd like to make sure those are tested.

I created a DataSet that has each type of role (there are about 15 roles in our app):

class EmployeeData(DataSet):

  class Meta:
    storable = Employee

  class engineer:
    username = "engineer"
    role = ROLE_ENGINEER

  class manager:
    username = "manager"
    role = ROLE_MANAGER

  class admin:
    username = "admin"
    role = ROLE_ADMIN

and what I'd like to do is write a functional test that checks only the right people can access a page. (The actual permissions are way more complicated, I just wanted a toy example to show you.)

Something like this:

def test_only_admin_can_see_this_page():

  for employee in Employee.query.all():
    login(employee)

    with self.app.test_request_context('/'):
    response = self.test_client.get(ADMIN_PAGE)
    if employee.role == ROLE_ADMIN
      eq_(200, response.status_code)
    else:
      eq_(401, response.status_code)

    logout(employee)

Is there a way to generate the fixture data so my devs don't have to remember to add a line to the fixtures every time we add a role? We have the canonical list of all roles as configuration elsewhere in the app, so I have that.

I'm not wedded to any of this or the fixture module, so I'm happy to hear suggestions!

Answer 1

An option would be to use factory_boy to create your test data.

• Assuming that you keep and update accordingly a list of roles (that will be used later on) like this one:

  roles = [ROLE_ENGINEER, ROLE_ADMIN, ROLE_MANAGER, ...]
  

• Let's create a factory for the Employee table:

  import factory
  from somewhere.in.the.app import roles
  
  class EmployeeFactory(factory.alchemy.SQLAlchemyModelFactory):
      class Meta:
          model = Employee
          sqlalchemy_session = session
  
      username = factory.Sequence(lambda n: u'User %d' % n)
      # Other attributes
      ...
      # Now the role choice
      role = factory.fuzzy.FuzzyChoice(roles)
  

  The FuzzyChoice method takes a list of choices and makes a random choice from this list.
  Now this will be able to create any amount of Employee objects on demand.

• Using the factory:

  from factory.location import EmployeeFactory
  
  def test_only_admin_can_see_this_page():
      EmployeeFactory.create_batch(size=100)
  
      for employee in session.query(Employee).all():
          login(employee)
  
          with self.app.test_request_context('/'):
          response = self.test_client.get(ADMIN_PAGE)
          if employee.role == ROLE_ADMIN
              eq_(200, response.status_code)
          else:
              eq_(401, response.status_code)
  
          logout(employee)
  

  Breakdown:

  • EmployeeFactory.create_batch(size=100) Creates 100 Employee objects in the test session.
  • We can access those objects from the factory session.

---

More information about using factory_boy with SQLAlchemy: https://factoryboy.readthedocs.io/en/latest/orms.html?highlight=sqlalchemy#sqlalchemy.
Be careful with session management especially: https://factoryboy.readthedocs.io/en/latest/orms.html?highlight=sqlalchemy#managing-sessions