Book Image

Django 1.1 Testing and Debugging

Book Image

Django 1.1 Testing and Debugging

Overview of this book

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.
Table of Contents (17 chapters)
Django 1.1 Testing and Debugging
Credits
About the Author
About the Reviewer
Preface
Index

Database query history


When DEBUG is True, Django maintains a history of all SQL commands sent to the database. This history is kept in a list, named queries, located in the django.db.connection module. The easiest way to see what is kept in this list is to examine it from a shell session:

>>> from django.db import connection 
>>> connection.queries 
[] 
>>> from survey.models import Survey 
>>> Survey.objects.count() 
2 
>>> connection.queries 
[{'time': '0.002', 'sql': u'SELECT COUNT(*) FROM "survey_survey"'}] 
>>> 

Here we see that queries is initially empty at the beginning of the shell session. We then retrieve a count of the number of Survey objects in the database, which comes back as 2. When we again display the contents of queries, we see that there is now one query in the queries list. Each element in the list is a dictionary containing two keys: time and sql. The value of time is how long, in seconds, the query took to execute...