Explain Django's testing framework and best practices.

Django testing framework:\n\n**Test Classes:**\n• TestCase - Full Django test case with database\n• TransactionTestCase - Test database transactions\n• SimpleTestCase - No database access\n• LiveServerTestCase - Runs live server\n\n**Test Methods:**\n• setUp() - Run before each test\n• tearDown() - Run after each test\n• setUpClass() - Run once before all tests\n\n**Assertions:**\n• assertEqual(), assertTrue(), assertFalse()\n• assertContains(), assertRedirects()\n• assertRaises(), assertTemplateUsed()\n\n**Best Practices:**\n• Use factories for test data\n• Mock external services\n• Test edge cases\n• Keep tests isolated\n• Use descriptive test names