SQLAlchemy-Fixture-Factory

A fixture factory for SQLAlchemy ORM mapper to easily build test scenarios for unit or integration testing. Inspired by Ruby's factory_girl

Installation

pip install sqlalchemy-fixture-factory

Usage

Assume following plain SQLAlchemy ORM models:

# association table
account_role = Table('account_role', Base.metadata,
                     Column('id_account', Integer, ForeignKey('account.id')),
                     Column('id_role', Integer, ForeignKey('role.id')))

class Role(Base):
    __tablename__ = 'role'

    id = Column(Integer, primary_key=True)
    name = Column(Unicode)

class Account(Base):
    __tablename__ = 'account'

    id = Column(Integer, primary_key=True)
    name = Column('name', Unicode)

    roles = relationship(Role, secondary=account_role)

class Person(Base):
    __tablename__ = 'person'

    id = Column(Integer, primary_key=True)
    first_name = Column('first_name', Unicode)
    account_id = Column(Integer, ForeignKey('account.id'))
    account = relationship(Account)

Initialize SQLAlchemy-Fixture-Factory:

# SQLAlechemy DB session generated from SessionPool
fix_fact = SqlaFixFact(db_session)

Define a simple person fixture:

class FranzPerson(BaseFix):
    MODEL = Person
    first_name = 'Franz'

The property MODEL needs to be set with the desired ORM class. Then simply set the fields as desired. In this example the first_name with Franz.

Use this fixture:

franz_fix = FranzPerson(fix_fact).create()

print ("Person count:", db_session.query(Person).count())
# output: 1

# create more instances of the same fixture
franz_fix_2 = FranzPerson(fix_fact).create()
franz_fix_3 = FranzPerson(fix_fact).create()

print ("Person count:", db_session.query(Person).count())
# output: 3

print ("Instances and id's are different:",
       franz_fix != franz_fix_2 != franz_fix_3,
       franz_fix.id != franz_fix_2.id != franz_fix_3.id)
# output: True True

# alter fields at instantiation time
franz_fix_alt_name = FranzPerson(fix_fact, first_name='Sepp').create()

print ("Person count with first_name 'Sepp':",
       db_session.query(Person).filter(Person.first_name == "Sepp").count())
# output: 1

Alternatively, retrieve the model without instantiating the fixture, but create the dependencies with .model()

# retrieve only the (altered) model
franz_model_alt_name = FranzPerson(fix_fact, first_name='Hugo').model()

print ("Person count with first_name 'Hugo':",
       db_session.query(Person).filter(Person.first_name == "Hugo").count())
# output: 0

db_session.add(franz_model_alt_name)

print ("Person count with first_name 'Hugo':",
       db_session.query(Person).filter(Person.first_name == "Hugo").count())
# output: 1

If you need the same instance in different fixtures, use .get()

# clean up the DB
Base.metadata.drop_all(connection)
Base.metadata.create_all(connection)

# first call creates the fixture and caches the reference
franz_get = FranzPerson(fix_fact).get()
franz_get_2 = FranzPerson(fix_fact).get()
franz_get_3 = FranzPerson(fix_fact).get()

print ("Person count:", db_session.query(Person).count())
# output: 1

print ("Instances and id's are the same:",
       franz_get == franz_get_2 == franz_get_3,
       franz_get.id == franz_get_2.id == franz_get_3.id)
# output: True True

Build a more complex scenario:

class ViewRole(BaseFix):
    MODEL = Role
    name = "View Role"

class EditRole(BaseFix):
    MODEL = Role
    name = "Edit Role"

class ArnoldAccount(BaseFix):
    MODEL = Account
    name = "arney"
    # Use get to reference to the roles, as only one instance in the DB is desired
    roles = [sqla_fix_fact.subFactoryGet(ViewRole), sqla_fix_fact.subFactoryGet(EditRole)]

class ArnoldPerson(BaseFix):
    MODEL = Person
    name = "Arnold"
    account = sqla_fix_fact.subFactoryModel(ArnoldAccount)

To instantiate the ArnoldPerson fixture, following line is sufficient to create the person with all dependencies:

arnold_fix = ArnoldPerson(fix_fact).create()

Query the DB to see if everything is in place as expected:

arnold_db = db_session.query(Person).get(arnold_fix.id)

print ("Account name of Arnold:", arnold_db.account.name)
# output: arney
print ("Roles of Arnold:", [r.name for r in arnold_db.account.roles])
# output: ['View Role', 'Edit Role']

You can find this examples ready to play around in readme_examples.py

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