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Add section about testing in Services
- Remove examples for testing services / selectors from the `Testing` section
This commit is contained in:
Radoslav Georgiev
parent
10eaba3319
commit
ce05847710
395
README.md
395
README.md
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@ -24,6 +24,7 @@ Django styleguide that we use in [HackSoft](https://hacksoft.io).
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* [Naming convention](#naming-convention)
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* [Modules](#modules)
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* [Selectors](#selectors)
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* [Testing](#testing-1)
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- [APIs & Serializers](#apis--serializers)
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* [Naming convention](#naming-convention-1)
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* [An example list API](#an-example-list-api)
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@ -38,14 +39,8 @@ Django styleguide that we use in [HackSoft](https://hacksoft.io).
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* [Raising Exceptions in Services / Selectors](#raising-exceptions-in-services--selectors)
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* [Handle Exceptions in APIs](#handle-exceptions-in-apis)
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* [Error formatting](#error-formatting)
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- [Testing](#testing-1)
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- [Testing](#testing-2)
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* [Naming conventions](#naming-conventions)
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* [Example](#example)
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+ [Example models](#example-models)
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+ [Example selectors](#example-selectors)
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+ [Example services](#example-services)
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* [Testing services](#testing-services)
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* [Testing selectors](#testing-selectors)
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- [Celery](#celery)
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* [Structure](#structure)
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+ [Configuration](#configuration)
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@ -469,6 +464,112 @@ As you can see, `users_get_visible_for` is another selector.
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You can return querysets, or lists or whatever makes sense to your specific case.
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### Testing
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Since services hold our business logic, they are an ideal candidate for tests.
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If you decide to cover the service layer with tests, we have few general rules of thumb to follow:
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1. The tests should cover the business logic behind the services in an exhaustive manner.
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1. The tests should hit the database - creating & reading from it.
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1. The tests should mock async task calls & everything that goes outside the project.
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When creating the required state for a given test, one can use a combination of:
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* Fakes (We recommend using [`faker`](https://github.com/joke2k/faker))
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* Other services, to create the required objects.
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* Special test utility & helper methods.
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* Factories (We recommend using [`factory_boy`](https://factoryboy.readthedocs.io/en/latest/orms.html))
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* Plain `Model.objects.create()` calls, if factories are not yet introduced in the project.
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* Usually, whatever suits you better.
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**Let's take a look at our service from the example:**
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```python
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from django.contrib.auth.models import User
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from django.core.exceptions import ValidationError
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from project.payments.selectors import items_get_for_user
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from project.payments.models import Item, Payment
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from project.payments.tasks import payment_charge
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def item_buy(
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*,
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item: Item,
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user: User,
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) -> Payment:
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if item in items_get_for_user(user=user):
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raise ValidationError(f'Item {item} already in {user} items.')
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payment = Payment.objects.create(
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item=item,
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user=user,
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successful=False
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)
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payment_charge.delay(payment_id=payment.id)
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return payment
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```
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The service:
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* Calls a selector for validation.
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* Creates an object.
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* Delays a task.
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**Those are our tests:**
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```python
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from unittest.mock import patch
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from django.test import TestCase
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from django.contrib.auth.models import User
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from django.core.exceptions import ValidationError
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from django_styleguide.payments.services import item_buy
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from django_styleguide.payments.models import Payment, Item
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class ItemBuyTests(TestCase):
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def setUp(self):
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self.user = User.objects.create_user(username='Test User')
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self.item = Item.objects.create(
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name='Test Item',
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description='Test Item description',
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price=10.15
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)
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@patch('project.payments.services.items_get_for_user')
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def test_buying_item_that_is_already_bought_fails(self, items_get_for_user_mock):
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"""
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Since we already have tests for `items_get_for_user`,
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we can safely mock it here and give it a proper return value.
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"""
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items_get_for_user_mock.return_value = [self.item]
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with self.assertRaises(ValidationError):
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item_buy(user=self.user, item=self.item)
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@patch('project.payments.services.payment_charge.delay')
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def test_buying_item_creates_a_payment_and_calls_charge_task(
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self,
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payment_charge_mock
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):
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self.assertEqual(0, Payment.objects.count())
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payment = item_buy(user=self.user, item=self.item)
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self.assertEqual(1, Payment.objects.count())
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self.assertEqual(payment, Payment.objects.first())
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self.assertFalse(payment.successful)
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payment_charge_mock.assert_called()
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```
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## APIs & Serializers
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When using services & selectors, all of your APIs should look simple & identical.
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@ -1101,286 +1202,6 @@ If we are to split the `utils.py` module into submodules, the same will happen f
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We try to match the structure of our modules with the structure of their respective tests.
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### Example
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We have a demo `django_styleguide` project.
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#### Example models
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```python
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import uuid
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from django.db import models
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from django.contrib.auth.models import User
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from django.utils import timezone
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from djmoney.models.fields import MoneyField
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class Item(models.Model):
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id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
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name = models.CharField(max_length=255)
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description = models.TextField()
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price = MoneyField(
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max_digits=14,
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decimal_places=2,
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default_currency='EUR'
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)
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def __str__(self):
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return f'Item {self.id} / {self.name} / {self.price}'
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class Payment(models.Model):
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item = models.ForeignKey(
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Item,
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on_delete=models.CASCADE,
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related_name='payments'
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)
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user = models.ForeignKey(
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User,
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on_delete=models.CASCADE,
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related_name='payments'
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)
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successful = models.BooleanField(default=False)
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created_at = models.DateTimeField(default=timezone.now)
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def __str__(self):
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return f'Payment for {self.item} / {self.user}'
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```
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#### Example selectors
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For implementation of `QuerySetType`, check `queryset_type.py`.
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```python
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from django.contrib.auth.models import User
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from django_styleguide.common.types import QuerySetType
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from django_styleguide.payments.models import Item
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def get_items_for_user(
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*,
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user: User
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) -> QuerySetType[Item]:
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return Item.objects.filter(payments__user=user)
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```
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#### Example services
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```python
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from django.contrib.auth.models import User
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from django.core.exceptions import ValidationError
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from django_styleguide.payments.selectors import get_items_for_user
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from django_styleguide.payments.models import Item, Payment
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from django_styleguide.payments.tasks import charge_payment
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def buy_item(
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*,
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item: Item,
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user: User,
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) -> Payment:
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if item in get_items_for_user(user=user):
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raise ValidationError(f'Item {item} already in {user} items.')
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payment = Payment.objects.create(
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item=item,
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user=user,
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successful=False
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)
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charge_payment.delay(payment_id=payment.id)
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return payment
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```
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### Testing services
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Service tests are the most important tests in the project. Usually, those are the heavier tests with most lines of code.
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General rule of thumb for service tests:
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* The tests should cover the business logic behind the services in an exhaustive manner.
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* The tests should hit the database - creating & reading from it.
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* The tests should mock async task calls & everything that goes outside the project.
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When creating the required state for a given test, one can use a combination of:
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* Fakes (We recommend using [`faker`](https://github.com/joke2k/faker))
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* Other services, to create the required objects.
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* Special test utility & helper methods.
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* Factories (We recommend using [`factory_boy`](https://factoryboy.readthedocs.io/en/latest/orms.html))
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* Plain `Model.objects.create()` calls, if factories are not yet introduced in the project.
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**Let's take a look at our service from the example:**
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```python
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from django.contrib.auth.models import User
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from django.core.exceptions import ValidationError
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from django_styleguide.payments.selectors import get_items_for_user
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from django_styleguide.payments.models import Item, Payment
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from django_styleguide.payments.tasks import charge_payment
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def buy_item(
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*,
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item: Item,
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user: User,
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) -> Payment:
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if item in get_items_for_user(user=user):
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raise ValidationError(f'Item {item} already in {user} items.')
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payment = Payment.objects.create(
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item=item,
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user=user,
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successful=False
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)
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charge_payment.delay(payment_id=payment.id)
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return payment
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```
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The service:
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* Calls a selector for validation
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* Creates ORM object
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* Calls a task
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**Those are our tests:**
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```python
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from unittest.mock import patch
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from django.test import TestCase
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from django.contrib.auth.models import User
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from django.core.exceptions import ValidationError
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from django_styleguide.payments.services import buy_item
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from django_styleguide.payments.models import Payment, Item
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class BuyItemTests(TestCase):
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def setUp(self):
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self.user = User.objects.create_user(username='Test User')
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self.item = Item.objects.create(
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name='Test Item',
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description='Test Item description',
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price=10.15
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)
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self.service = buy_item
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@patch('django_styleguide.payments.services.get_items_for_user')
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def test_buying_item_that_is_already_bought_fails(self, get_items_for_user_mock):
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"""
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Since we already have tests for `get_items_for_user`,
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we can safely mock it here and give it a proper return value.
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"""
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get_items_for_user_mock.return_value = [self.item]
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with self.assertRaises(ValidationError):
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self.service(user=self.user, item=self.item)
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@patch('django_styleguide.payments.services.charge_payment.delay')
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def test_buying_item_creates_a_payment_and_calls_charge_task(
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self,
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charge_payment_mock
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):
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self.assertEqual(0, Payment.objects.count())
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payment = self.service(user=self.user, item=self.item)
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self.assertEqual(1, Payment.objects.count())
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self.assertEqual(payment, Payment.objects.first())
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self.assertFalse(payment.successful)
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charge_payment_mock.assert_called()
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```
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### Testing selectors
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Testing selectors is also an important part of every project.
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Sometimes, the selectors can be really straightforward, and if we have to "cut corners", we can omit those tests. But it the end, it's important to cover our selectors too.
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Let's take another look at our example selector:
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```python
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from django.contrib.auth.models import User
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from django_styleguide.common.types import QuerySetType
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from django_styleguide.payments.models import Item
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def get_items_for_user(
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*,
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user: User
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) -> QuerySetType[Item]:
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return Item.objects.filter(payments__user=user)
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```
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As you can see, this is a very straightforward & simple selector. We can easily cover that with 2 to 3 tests.
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**Here are the tests:**
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```python
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from django.test import TestCase
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from django.contrib.auth.models import User
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from django_styleguide.payments.selectors import get_items_for_user
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from django_styleguide.payments.models import Item, Payment
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class GetItemsForUserTests(TestCase):
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def test_selector_returns_nothing_for_user_without_items(self):
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"""
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This is a "corner case" test.
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We should get nothing if the user has no items.
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"""
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user = User.objects.create_user(username='Test User')
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expected = []
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result = list(get_items_for_user(user=user))
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self.assertEqual(expected, result)
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def test_selector_returns_item_for_user_with_that_item(self):
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"""
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This test will fail in case we change the model structure.
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"""
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user = User.objects.create_user(username='Test User')
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item = Item.objects.create(
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name='Test Item',
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description='Test Item description',
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price=10.15
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)
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Payment.objects.create(
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item=item,
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user=user
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)
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expected = [item]
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result = list(get_items_for_user(user=user))
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self.assertEqual(expected, result)
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```
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## Celery
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We use [Celery](http://www.celeryproject.org/) for the following general cases:
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