A Tool for creating testing scenarios
Having fixtures or test scenarios defined in re-usable, combinable, shareable ways is a good thing as well as having them in a format that doesn't require coding abilities to understand them. Thats what scenarious offers
pip install scenarious
pip install -e git+https://github.com/sebastiandev/scenarious@development
pip install -e git+https://github.com/sebastiandev/scenarious@python-2.7
We can create a yaml file that will describe our data or we can create it as a StringIO in your unit test. Both approaches will look the same, we need to define our data types and start specifying our test scenario:
actors:
- name: John Travolta
age: 64
- name: Brad Pitt
age: 55
- name: Edward Norton
age: 49
- name: Hugh Jackman
age: 50
genres:
- name: Action
- name: Drama
movies:
- title: Pulp Fiction
year: 1994
genre: $genre_1
actors:
- $actor_1
- title: Fight Club
year: 1999
genre: $genre_1
actors:
- $actor_2
- $actor_3
- title: The Fountain
year: 2006
genre: $genre_2
actors:
- $actor_4That's it, and is quite self descriptive, but there are some tricks there...
First thing one notices is that there seem to be some sort of relationship between the types, and that happens pretty often when modelling entities, in scenarious we repsent references like this:
${entity_type}_{id_or_alias}
For the case of the movies
movies:
- title: Pulp Fiction
year: 1994
genre: $genre_1
actors:
- $actor_1$actor_1 is referencing the actor with id 1. If we didnt define an id on the actors, then the id is automatically generated by the order in which they are processed. So the actor 1 is John Travolta
When assigning values to attributes we could want to assign the value of an existing entity, so instead of referencing the entire entity, we'd just want the entitie's attribute. So we can use the referencing and add the attribute we want:
${entity_typ}]_{id_or_alias}.{attribute_name}
There's no limit in the depth of hops or relationship chain, as long as they are defined in your models then they can be navigated and referenced.
Each model that you use/define in a scenario needs to have a TypeHandler which is the resposible of creating the actual entity in the database, passing all the required attributes, applying defaults and defining required fields to be defined by the user, if any.
class MovieHandler(TypeHandler):
__type_name__ = 'movie'
__requires__ = ['title', 'genre', 'actors']
year = lambda: faker.year()
director = lambda: faker.random_sample(['Scorsese', 'Tarantino', 'Spielberg', 'Ridley Scott'], 1)
studio = lambda: faker.random_sample(['Universal', 'MGM', 'DreamWorks', 'Disney'], 1)
budget = lambda: Decimal(faker.random_int(10000, 50000000))
Here you can see that movie required the user to define the title, genre and actors fields, the rest are all randomly generated using the faker library
When using sqlalchemy the type handler definition needs to know the model you are referring to in the schema, so we need to use the SQLALchemyTypeHandler and expect models to have a .create(**kwargs) method.
from scenarious.sql_alchemy import SQLALchemyTypeHandler
class MovieHandler(SQLALchemyTypeHandler):
__type_name__ = 'movie'
__model__ = Movie # what ever model you have defined for your movies
__requires__ = ['title', 'genre', 'actors']
year = lambda: faker.year()
director = lambda: faker.random_sample(['Scorsese', 'Tarantino', 'Spielberg', 'Ridley Scott'], 1)
studio = lambda: faker.random_sample(['Universal', 'MGM', 'DreamWorks', 'Disney'], 1)
budget = lambda: Decimal(faker.random_int(10000, 50000000))If there's some custom logic needed for the entity creation, you can extend/override the ._do_create(self, data) method as well as the constructor
Now we have to actually tell scenarious to load this scenario into our database
from StringIO import StringIO
from scenarious import Scenario, TypeHandler
class MovieHandler(TypeHandler):
__type_name__ = 'movie'
__requires__ = ['title', 'genre', 'actors']
year = lambda: faker.year()
director = lambda: faker.random_sample(['Scorsese', 'Tarantino', 'Spielberg', 'Ridley Scott'], 1)
studio = lambda: faker.random_sample(['Universal', 'MGM', 'DreamWorks', 'Disney'], 1)
budget = lambda: Decimal(faker.random_int(10000, 50000000))
class ActorHandler(TypeHandler):
__type_name__ = 'actor'
__requires__ = ['name']
age = lambda: faker.random_int(20, 80)
class GenreHandler(TypeHandler):
__type_name__ = 'genre'
__requires__ = ['title']
scenario = Scenario.load(StringIO("""
actors:
- name: John Travolta
age: 64
- name: Brad Pitt
age: 55
- name: Edward Norton
age: 49
- name: Huge Jackman
age: 50
genres:
- name: Action
- name: Drama
movies:
- title: Pulp Fiction
year: 1994
genre: $genre_1
actors:
- $actor_1
- title: Fight Club
year: 1999
genre: $genre_1
actors:
- $actor_2
- $actor_3
- title: The Fountain
year: 2006
genre: $genre_2
actors:
- $actor_4
"""), type_handlers=[MovieTypeHandler, ActorTypeHandler, GenreTypeHandler)And you are done, the database already has the actors, genres and movies. You can now start testing your app.
As an application grows, you will probably have many type handlers and having to manually specify each one of them when loading the scenario is a bit verbose. So that why a TypeHandlerLoader exists. There are two ways of loading you handlers
from scenarious import TypeHandlerLoader
from scenarious.utils import module_dir
# Option 1
handlers = TypeHandlerLoader.load('/some/path/to/your/app')
# Option 2
class CustomTypeHandlerLoader(TypeHandlerLoader):
group_path = module_dir(__file__) # if they are all in the same folder
# Option 3
class CustomTypeHandlerLoader(TypeHandlerLoader):
group_path = ['/some/path/', '/another/path'] # if you have them in different places
handlers = CustomTypeHandlerLoader.load()In order to make scenarious even easier to use for testing, there's a base class for your tests that provides with shortcuts to initialize and create scenarios, as well as a decorator to create scenarios for specific test methods
There's the ScenariousBaseTest class that provides a few shortcuts for creating the scenarios and accesing the entities
from unittest import BaseTest
from scenarious import testing, Scenario
class CustomTest(BaseTest, testing.ScenariousBaseTest):
scenario_handler = Scenario # you can specify you own class that extends Scenario here to be used in the tests
type_handler_loader = CustomTypeHandlerLoader # the custom loader we created above
def setUp(self):
self.create_scenario("""
actors:
- name: John Travolta
alias: John
age: 64
- name: Brad Pitt
alias: Brad
age: 55
- name: Edward Norton
alias: Ed
age: 49
""")
def test_actors(self):
assert 3 == self.actors # we are accessing all the actors
assert 'Edward Norton' == self.actors[2].name # we access by order of definition
assert 'Edward Norton' == self._scenario.by_id('actor', 'Ed').name # we access by aliasThere's also a decorator to be able to create specific scenarios for single test methods. The decorator can be used with a subclass of ScenariousBaseTest and without it, but in that case you will need to specify which scenario class to use and the type handlers
from unittest import BaseTest
from scenarious import testing, Scenario
class CustomTest(BaseTest, testing.ScenariousBaseTest):
scenario_handler = Scenario # you can specify you own class that extends Scenario here to be used in the tests
type_handler_loader = CustomTypeHandlerLoader # the custom loader we created above
@testing.scenario("""
actors:
- name: John Travolta
alias: John
age: 66
- name: Brad Pitt
alias: Brad
age: 55
- name: Edward Norton
alias: Ed
age: 51
""")
def test_actors_with_decorator(self):
assert 3 == self.actors # we are accessing all the actors
assert 'Edward Norton' == self.actors[2].name # we access by order of definition
assert 'Edward Norton' == self.by_id('actor', 'Ed').name # we access by alias
class PlainTest(BaseTest):
@testing.scenario("""
actors:
- name: John Travolta
alias: John
age: 66
- name: Brad Pitt
alias: Brad
age: 55
- name: Edward Norton
alias: Ed
age: 51
""", scenario_class=Scenario, handlers=[ActorTypeHandler])
def test_actors_with_decorator(self, scenario):
# If we are not subclassing ScenariousBaseTest, then we need to specidy
# the Scenario class we wantn to use as well as the handlers
assert 3 == scenario.actors # we are accessing all the actors
assert 'Edward Norton' == scenario.actors[2].name # we access by order of definition
assert 'Edward Norton' == scenario.by_id('actor', 'Ed').name # we access by alias