Django 1.1 Testing and Debugging

Karen M. Tracey

• Publisher: Packt Publishing
• Year: 2010
• eBook ISBN: 9781847197566
• Edition: 1
• Topic: Computer Science
• Subtopic: Application Development
• Index: Computer Science

In Detail

Bugs are a time consuming burden during software development.  Django's built-in test framework and debugging support help lessen this burden. This book will teach you quick and efficient techniques for using Django and Python tools to eradicate bugs and ensure your Django application works correctly.This book will walk you step by step through development of a complete sample Django application. You will learn how best to test and debug models, views, URL configuration, templates, and template tags. This book will help you integrate with and make use of the rich external environment of test and debugging tools for Python and Django applications.The book starts with a basic overview of testing. It will highlight areas to look out for while testing. You will learn about different kinds of tests available, and the pros and cons of each, and also details of test extensions provided by Django that simplify the task of testing Django applications. You will see an illustration of how external tools that provide even more sophisticated testing features can be integrated into Django's framework.On the debugging front, the book illustrates how to interpret the extensive debugging information provided by Django's debug error pages, and how to utilize logging and other external tools to learn what code is doing.

A step-by-step guide to running tests using Django's test support and making best use of Django and Python debugging tools

Approach

This book teaches by example. It walks in detail through development of a sample application, illustrating each step via complete working code and either screenshots or console snippets. The cumbersome and time consuming task of debugging will be a cake walk with this book.

Who this book is for

If you are a Django application developer who wants to create robust applications quickly that work well and are easy to maintain in the long term, this book is for you. This book is the right pick if you want to be smartly tutored to make best use of Django's rich testing and debugging support and make testing an effortless task.Basic knowledge of Python, Django, and the overall structure of a database-driven web application is assumed. However, the code samples are fully explained so that even beginners who are new to the area can learn a great deal from this book.

Django 1.1 Testing and Debugging

Karen M. Tracey

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Table of Contents

Django 1.1 Testing and Debugging

Credits

About the Author

About the Reviewer

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Errata

Piracy

Questions

1. Django Testing Overview

Getting started: Creating a new application

Understanding the sample unit test

Understanding the sample doctest

Running the sample tests

Breaking things on purpose

Test errors versus test failures

Command line options for running tests

Verbosity

Settings

Pythonpath

Traceback

Noinput

Version

Summary

2. Does This Code Work? Doctests in Depth

The Survey application models

Testing the Survey model

Testing Survey model creation

Is that test useful?

Developing a custom Survey save method

Deciding what to test

Some pros and cons of doctests so far

Additional doctest caveats

Beware of environmental dependence

Beware of database dependence

Beware of test interdependence

Beware of Unicode

Summary

3. Testing 1, 2, 3: Basic Unit Testing

Unit tests for the Survey save override method

Pros of the unit test version

Cons of the unit test version

Revisiting the doctest caveats

Environmental dependence

Database dependence

Test interdependence

Unicode

Providing data for unit tests

Providing data in test fixtures

Example test that needs test data

Using the admin application to create test data

Writing the function itself

Writing a test that uses the test data

Extracting the test data from the database

Getting the test data loaded during the test run

Creating data during test set up

Summary

4. Getting Fancier: Django Unit Test Extensions

Organizing tests

Creating the survey application home page

Defining the survey application URLs

Developing views to serve pages

Creating templates for pages

Testing the survey home page

Creating the survey detail pages

Refining the survey detail view

Templates for the survey detail pages

Basic testing of the survey detail pages

Customizing the admin add and change survey pages

Developing a custom survey form

Configuring admin to use the custom form

Testing the admin customization

Additional test support

Supporting additional HTTP methods

Maintaining persistent state

E-mail services

Providing test-specific URL configuration

Response context and template information

Testing transactional behavior

Summary

5. Filling in the Blanks: Integrating Django and Other Test Tools

Problems of integration

Specifying an alternative test runner

Creating a new management command

How much of the code are we testing?

Using coverage standalone

Integrating coverage into a Django project

The twill web browsing and testing tool

Using the twill command line program

Using twill in a TestCase

Summary

6. Django Debugging Overview

Django debug settings

The DEBUG and TEMPLATE_DEBUG settings

The TEMPLATE_STRING_IF_INVALID setting

Debug error pages

Database query history

Debug support in the development server

Handling problems in production

Creating general error pages

Reporting production error information

Internal server error notifications

Page not found notifications

Summary

7. When the Wheels Fall Off: Understanding a Django Debug Page

Starting the Survey voting implementation

Creating test data for voting

Defining a question form for voting

Debug page #1: TypeError at /

Elements of the debug page

Basic error information

Traceback

Request information

GET

POST

FILES

COOKIES

META

Settings

Understanding and fixing the TypeError

Handling multiple Survey questions

Creating the data for multiple questions

Coding support for multiple questions

Debug page #2: TemplateSyntaxError at /1/

Understanding and fixing the TemplateSyntaxError

Recording Survey responses

Coding support for recording Survey responses

Debug page #3: NoReverseMatch at /1/

Understanding and fixing the NoReverseMatch exception

Debug page #4: TemplateDoesNotExist at /thanks/1/

Understanding and fixing TemplateDoesNotExist

Handling invalid Survey submissions

Coding custom error message and placement

Debug page #5: Another TemplateSyntaxError

Fixing the second TemplateSyntaxError

Summary

8. When Problems Hide: Getting More Information

Tracking SQL queries for a request

Settings for accessing query history in templates

SQL queries for the home page

Packaging the template query display for reuse

Testing the repackaged template code

SQL queries for the active Survey form display page

SQL queries for posting survey answers

The Django Debug Toolbar

Installing the Django Debug Toolbar

Debug toolbar appearance

The SQL panel

The Time panel

The Settings panel

The HTTP Headers panel

The Request Vars panel

The Templates panel

The Signals panel

The Logging panel

Redirect handling by the debug toolbar

Tracking internal code state

Resist the urge to sprinkle prints

Simple logging configuring for development

Deciding what to log

Decorators to log function entry and exit

Applying the decorators to the Survey code

Logging in the debug toolbar

Summary

9. When You Don't Even Know What to Log: Using Debuggers

Implementing the Survey results display

Results display using pygooglechart

Getting started with the debugger

The list command

The where command

The args command

The whatis command

The print and pp commands

Debugging the pygooglechart results display

The step and next commands

The continue command

The jump command

The break command

The clear command

Fixing the pygooglechart results display

The up and down commands

The return command

Results display using matplotlib

Improving the matplotlib approach

Setting up static file serving

Dynamically generating image files

Dealing with race conditions

Using the debugger to force race situations

Notes on using graphical debuggers

Summary

10. When All Else Fails: Getting Outside Help

Tracking down a problem in Django

Revisiting the Chapter 7 voting form

Is the right code actually running?

Is the code correct as per the documentation?

Searching for a matching problem report

Another way to search for a matching problem report

Determining the release that contains a fix

What if a fix hasn't been released yet?

What if a fix hasn't been committed yet?

What if a ticket has been closed without a fix?

Tracking down unreported problems

Where to ask questions

Tips on asking questions that will get good answers

Opening a new ticket to report a problem

Summary

11. When it's Time to Go Live: Moving to Production

Developing an Apache/mod_wsgi configuration

Creating the WSGI script for the marketr project

Creating an Apache VirtualHost for the marketr project

Activating the new Apache configuration

Debugging the new Apache configuration

Configuring Apache to serve static files

Testing multithreaded behavior

Generating load with siege

Load testing the results recording code

Fixing the results recording code

Additional load testing notes

Using Apache/mod_wsgi during development

Summary

Index

Django 1.1 Testing and Debugging

Copyright © 2010 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author nor Packt Publishing,...

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• Django 1.1 Testing and Debugging