Turbogears quirks when testing controllers that use SingleSelectField

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Suppose you have a User that can be a member of a Company. In SQLObject you model it somehow like this:

    class Company(SQLObject):
        name = UnicodeCol(length=16, alternateID=True, alternateMethodName="by_name")
        display_name = UnicodeCol(length=255)

    class User(InheritableSQLObject):
        company = ForeignKey("Company", notNull=False, cascade='null')

Then you want to make a form that allows to choose what is the company of a user:

def companies():
    return [ [ -1, 'None' ] ] + [ [c.id, c.display_name] for c in Company.select() ]

class NewUserFields(WidgetsList):
    """Fields for editing general settings"""
    user_name = TextField(label="User name")
    companyID = SingleSelectField(label="Company", options=companies)

Ok. Now you want to run tests:

  1. nosetests imports the controller to see if there's any initialisation code.
  2. The NewUserFields class is created.
  3. The SingleSelectField is created.
  4. The SingleSelectField constructor tries to guess the validator and peeks at the first option.
  5. This calls companies.
  6. companies accesses the database.
  7. The testing database has not yet been created because nosetests imported the module before giving the test code a chance to setup the test database.
  8. Bang.

The solution is to add an explicit validator to disable this guessing code that is a source of so many troubles:

class NewUserFields(WidgetsList):
    """Fields for editing general settings"""
    user_name = TextField(label="User name")
    companyID = SingleSelectField(label="Company", options=companies, validator=v.Int(not_empty=True))