Code-Memo

Writing and Running Tests

1. Introduction to Testing in Django

Django comes with a built-in testing framework based on Python’s unittest module. Tests help verify that code works as expected and prevent regressions when making changes.

Tests are written inside a Django app, typically in tests.py, or within a dedicated tests/ directory.

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2. Setting Up Tests

By default, Django creates a test database before running tests. This ensures tests don’t affect the production database.

To create tests, import Django’s TestCase class:

from django.test import TestCase
from myapp.models import Item

class ItemTestCase(TestCase):
    def setUp(self):
        Item.objects.create(name="Laptop", price=1200)
        Item.objects.create(name="Phone", price=800)

    def test_item_names(self):
        """Test that item names are stored correctly"""
        laptop = Item.objects.get(name="Laptop")
        phone = Item.objects.get(name="Phone")
        self.assertEqual(laptop.name, "Laptop")
        self.assertEqual(phone.name, "Phone")

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3. Running Tests

Run all tests using:

python manage.py test

Run tests for a specific app:

python manage.py test myapp

Run a specific test case:

python manage.py test myapp.tests.ItemTestCase

Run a specific test method:

python manage.py test myapp.tests.ItemTestCase.test_item_names

To see detailed output, use the -v flag:

python manage.py test -v 2

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4. Writing Test Cases

Django provides TestCase, SimpleTestCase, TransactionTestCase, and LiveServerTestCase for different testing needs.

a) Model Tests

Testing models ensures database interactions work correctly.

from django.test import TestCase
from myapp.models import Product

class ProductModelTest(TestCase):
    def setUp(self):
        self.product = Product.objects.create(name="Keyboard", price=50)

    def test_product_str(self):
        """Test the string representation of the model"""
        self.assertEqual(str(self.product), "Keyboard")

    def test_product_price(self):
        """Ensure product price is stored correctly"""
        self.assertEqual(self.product.price, 50)

b) View Tests

Testing views ensures that URLs return the expected responses.

from django.test import TestCase
from django.urls import reverse
from myapp.models import Product

class ProductViewTest(TestCase):
    def setUp(self):
        self.product = Product.objects.create(name="Mouse", price=20)

    def test_product_list_view(self):
        response = self.client.get(reverse("product-list"))
        self.assertEqual(response.status_code, 200)
        self.assertContains(response, "Mouse")

    def test_product_detail_view(self):
        response = self.client.get(reverse("product-detail", args=[self.product.id]))
        self.assertEqual(response.status_code, 200)
        self.assertContains(response, "Mouse")

c) Form Tests

Testing forms ensures validation and processing work as expected.

from django.test import TestCase
from myapp.forms import ProductForm

class ProductFormTest(TestCase):
    def test_valid_form(self):
        form = ProductForm(data={"name": "Monitor", "price": 200})
        self.assertTrue(form.is_valid())

    def test_invalid_form(self):
        form = ProductForm(data={"name": "", "price": -10})
        self.assertFalse(form.is_valid())

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5. Using Assertions

Django’s TestCase includes many useful assertions:

• assertEqual(a, b): Check if a == b.
• assertNotEqual(a, b): Check if a != b.
• assertTrue(x): Check if x is True.
• assertFalse(x): Check if x is False.
• assertIsNone(x): Check if x is None.
• assertContains(response, text): Check if text is in response content.
• assertRedirects(response, url): Check if a view redirects correctly.

Example:

def test_product_price(self):
    self.assertEqual(self.product.price, 50)
    self.assertNotEqual(self.product.price, 100)

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6. Using setUpTestData

For performance improvements, use setUpTestData() instead of setUp(). It runs only once per test class instead of before every test method.

class ProductTestCase(TestCase):
    @classmethod
    def setUpTestData(cls):
        cls.product = Product.objects.create(name="Tablet", price=300)

    def test_product_name(self):
        self.assertEqual(self.product.name, "Tablet")

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7. Skipping Tests

Sometimes, tests need to be skipped. Use @unittest.skip decorators:

from django.test import TestCase
import unittest

class MyTests(TestCase):
    @unittest.skip("Skipping this test temporarily")
    def test_todo_feature(self):
        self.assertEqual(1, 1)

    @unittest.expectedFailure
    def test_failing_case(self):
        self.assertEqual(1, 2)  # This will be marked as expected failure

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8. Measuring Test Coverage

To ensure all code paths are tested, use coverage.py:

pip install coverage
coverage run manage.py test
coverage report -m

For an HTML report:

coverage html
open htmlcov/index.html