[Test-Driven Development with Python 01] • Test-Driven Development With Python · 1st Edition by Percival, Harry J.W. -- Read -- Imperial Library of Trantor

Index

Test-Driven Development with Python Dedication Preface

Why I Wrote a Book About Test-Driven Development Aims of This Book Outline Conventions Used in This Book Using Code Examples Safari® Books Online Contacting O’Reilly

Prerequisites and Assumptions

Python 3 and Programming How HTML Works JavaScript Required Software Installations

Git’s Default Editor, and Other Basic Git Config Required Python Modules

Acknowledgments I. The Basics of TDD and Django

1. Getting Django Set Up Using a Functional Test

Obey the Testing Goat! Do Nothing Until You Have a Test Getting Django Up and Running Starting a Git Repository

2. Extending Our Functional Test Using the unittest Module

Using a Functional Test to Scope Out a Minimum Viable App The Python Standard Library’s unittest Module Implicit waits Commit

3. Testing a Simple Home Page with Unit Tests

Our First Django App, and Our First Unit Test Unit Tests, and How They Differ from Functional Tests Unit Testing in Django Django’s MVC, URLs, and View Functions At Last! We Actually Write Some Application Code! urls.py Unit Testing a View

The Unit-Test/Code Cycle

4. What Are We Doing with All These Tests?

Programming Is like Pulling a Bucket of Water up from a Well Using Selenium to Test User Interactions The “Don’t Test Constants” Rule, and Templates to the Rescue

Refactoring to Use a Template

On Refactoring A Little More of Our Front Page Recap: The TDD Process

5. Saving User Input

Wiring Up Our Form to Send a POST Request Processing a POST Request on the Server Passing Python Variables to Be Rendered in the Template Three Strikes and Refactor The Django ORM and Our First Model

Our First Database Migration The Test Gets Surprisingly Far A New Field Means a New Migration

Saving the POST to the Database Redirect After a POST

Better Unit Testing Practice: Each Test Should Test One Thing

Rendering Items in the Template Creating Our Production Database with migrate

6. Getting to the Minimum Viable Site

Ensuring Test Isolation in Functional Tests

Running Just the Unit Tests

Small Design When Necessary

YAGNI! REST

Implementing the New Design Using TDD Iterating Towards the New Design Testing Views, Templates, and URLs Together with the Django Test Client

A New Test Class A New URL A New View Function

Green? Refactor

A Separate Template for Viewing Lists

Another URL and View for Adding List Items

A Test Class for New List Creation A URL and View for New List Creation Removing Now-Redundant Code and Tests Pointing Our Forms at the New URL

Adjusting Our Models

A Foreign Key Relationship Adjusting the Rest of the World to Our New Models

Each List Should Have Its Own URL

Capturing Parameters from URLs Adjusting new_list to the New World

One More View to Handle Adding Items to an Existing List

Beware of Greedy Regular Expressions! The Last New URL The Last New View But How to Use That URL in the Form?

A Final Refactor Using URL includes

II. Web Development Sine Qua Nons

7. Prettification: Layout and Styling, and What to Test About It

What to Functionally Test About Layout and Style Prettification: Using a CSS Framework Django Template Inheritance Integrating Bootstrap

Rows and Columns

Static Files in Django

Switching to StaticLiveServerCase

Using Bootstrap Components to Improve the Look of the Site

Jumbotron! Large Inputs Table Styling

Using Our Own CSS What We Glossed Over: collectstatic and Other Static Directories A Few Things That Didn’t Make It

8. Testing Deployment Using a Staging Site

TDD and the Danger Areas of Deployment As Always, Start with a Test Getting a Domain Name Manually Provisioning a Server to Host Our Site

Choosing Where to Host Our Site Spinning Up a Server User Accounts, SSH, and Privileges Installing Nginx Configuring Domains for Staging and Live Using the FT to Confirm the Domain Works and Nginx Is Running

Deploying Our Code Manually

Adjusting the Database Location Creating a Virtualenv Simple Nginx Configuration Creating the Database with migrate

Getting to a Production-Ready Deployment

Switching to Gunicorn Getting Nginx to Serve Static Files Switching to Using Unix Sockets Switching DEBUG to False and Setting ALLOWED_HOSTS Using Upstart to Make Sure Gunicorn Starts on Boot Saving Our Changes: Adding Gunicorn to Our requirements.txt

Automating

“Saving Your Progress”

9. Automating Deployment with Fabric

Breakdown of a Fabric Script for Our Deployment Trying It Out

Deploying to Live Nginx and Gunicorn Config Using sed

Git Tag the Release Further Reading

10. Input Validation and Test Organisation

Validation FT: Preventing Blank Items

Skipping a Test Splitting Functional Tests out into Many Files Running a Single Test File Fleshing Out the FT

Using Model-Layer Validation

Refactoring Unit Tests into Several Files Unit Testing Model Validation and the self.assertRaises Context Manager A Django Quirk: Model Save Doesn’t Run Validation

Surfacing Model Validation Errors in the View

Checking Invalid Input Isn’t Saved to the Database

Django Pattern: Processing POST Requests in the Same View as Renders the Form

Refactor: Transferring the new_item Functionality into view_list Enforcing Model Validation in view_list

Refactor: Removing Hardcoded URLs

The {% url %} Template Tag Using get_absolute_url for Redirects

11. A Simple Form

Moving Validation Logic into a Form

Exploring the Forms API with a Unit Test Switching to a Django ModelForm Testing and Customising Form Validation

Using the Form in Our Views

Using the Form in a View with a GET Request A Big Find and Replace

Using the Form in a View That Takes POST Requests

Adapting the Unit Tests for the new_list View Using the Form in the View Using the Form to Display Errors in the Template

Using the Form in the Other View

A Helper Method for Several Short Tests

Using the Form’s Own Save Method

12. More Advanced Forms

Another FT for Duplicate Items

Preventing Duplicates at the Model Layer A Little Digression on Queryset Ordering and String Representations Rewriting the Old Model Test Some Integrity Errors Do Show Up on Save

Experimenting with Duplicate Item Validation at the Views Layer A More Complex Form to Handle Uniqueness Validation Using the Existing List Item Form in the List View

13. Dipping Our Toes, Very Tentatively, into JavaScript

Starting with an FT Setting Up a Basic JavaScript Test Runner Using jQuery and the Fixtures Div Building a JavaScript Unit Test for Our Desired Functionality Javascript Testing in the TDD Cycle Columbo Says: Onload Boilerplate and Namespacing A Few Things That Didn’t Make It

14. Deploying Our New Code

Staging Deploy Live Deploy What to Do If You See a Database Error Wrap-Up: git tag the New Release

III. More Advanced Topics

15. User Authentication, Integrating Third-Party Plugins, and Mocking with JavaScript

Mozilla Persona (BrowserID) Exploratory Coding, aka “Spiking”

Starting a Branch for the Spike Frontend and JavaScript Code The Browser-ID Protocol The Server Side: Custom Authentication

De-spiking

A Common Selenium Technique: Explicit Waits Reverting Our Spiked Code

JavaScript Unit Tests Involving External Components: Our First Mocks!

Housekeeping: A Site-Wide Static Files Folder Mocking: Who, Why, What? Namespacing A Simple Mock to Unit Tests Our initialize Function More Advanced Mocking

Using a sinon.js mock to check we call the API correctly

Checking Call Arguments QUnit setup and teardown, Testing Ajax

Logout

More Nested Callbacks! Testing Asynchronous Code

16. Server-Side Authentication and Mocking in Python

A Look at Our Spiked Login View Mocking in Python

Testing Our View by Mocking Out authenticate Checking the View Actually Logs the User In

De-spiking Our Custom Authentication Backend: Mocking Out an Internet Request

1 if = 1 More Test Patching at the Class Level Beware of Mocks in Boolean Comparisons Creating a User if Necessary The get_user Method

A Minimal Custom User Model

A Slight Disappointment Tests as Documentation Users Are Authenticated

The Moment of Truth: Will the FT Pass? Finishing Off Our FT, Testing Logout

17. Test Fixtures, Logging, and Server-Side Debugging

Skipping the Login Process by Pre-creating a Session

Checking It Works

The Proof Is in the Pudding: Using Staging to Catch Final Bugs

Setting Up Logging Fixing the Persona Bug

Managing the Test Database on Staging

A Django Management Command to Create Sessions Getting the FT to Run the Management Command on the Server An Additional Hop via subprocess

Baking In Our Logging Code

Using Hierarchical Logging Config

Wrap-Up

18. Finishing “My Lists”: Outside-In TDD

The Alternative: “Inside Out” Why Prefer “Outside-In”? The FT for “My Lists” The Outside Layer: Presentation and Templates Moving Down One Layer to View Functions (the Controller) Another Pass, Outside-In

A Quick Restructure of the Template Inheritance Hierarchy Designing Our API Using the Template Moving Down to the Next Layer: What the View Passes to the Template

The Next “Requirement” from the Views Layer: New Lists Should Record Owner

A Decision Point: Whether to Proceed to the Next Layer with a Failing Test

Moving Down to the Model Layer

Final Step: Feeding Through the .name API from the Template

19. Test Isolation, and “Listening to Your Tests”

Revisiting Our Decision Point: The Views Layer Depends on Unwritten Models Code A First Attempt at Using Mocks for Isolation

Using Mock side_effects to Check the Sequence of Events

Listen to Your Tests: Ugly Tests Signal a Need to Refactor Rewriting Our Tests for the View to Be Fully Isolated

Keep the Old Integrated Test Suite Around as a Sanity Check A New Test Suite with Full Isolation Thinking in Terms of Collaborators

Moving Down to the Forms Layer

Keep Listening to Your Tests: Removing ORM Code from Our Application

Finally, Moving Down to the Models Layer

Back to Views

The Moment of Truth (and the Risks of Mocking) Thinking of Interactions Between Layers as “Contracts”

Identifying Implicit Contracts Fixing the Oversight

One More Test Tidy Up: What to Keep from Our Integrated Test Suite

Removing Redundant Code at the Forms Layer Removing the Old Implementation of the View Removing Redundant Code at the Forms Layer

Conclusions: When to Write Isolated Versus Integrated Tests

Let Complexity Be Your Guide Should You Do Both? Onwards!

20. Continuous Integration (CI)

Installing Jenkins

Configuring Jenkins Security Adding Required Plugins

Telling Jenkins where to find Python 3 and Xvfb

Setting Up Our Project First Build! Setting Up a Virtual Display so the FTs Can Run Headless Taking Screenshots A Common Selenium Problem: Race Conditions Running Our QUnit JavaScript Tests in Jenkins with PhantomJS

Installing node Adding the Build Steps to Jenkins

More Things to Do with a CI Server

21. The Token Social Bit, the Page Pattern, and an Exercise for the Reader

An FT with Multiple Users, and addCleanup Implementing the Selenium Interact/Wait Pattern The Page Pattern Extend the FT to a Second User, and the “My Lists” Page An Exercise for the Reader

22. Fast Tests, Slow Tests, and Hot Lava

Thesis: Unit Tests Are Superfast and Good Besides That

Faster Tests Mean Faster Development The Holy Flow State Slow Tests Don’t Get Run as Often, Which Causes Bad Code We’re Fine Now, but Integrated Tests Get Slower Over Time Don’t Take It from Me And Unit Tests Drive Good Design

The Problems with “Pure” Unit Tests

Isolated Tests Can Be Harder to Read and Write Isolated Tests Don’t Automatically Test Integration Unit Tests Seldom Catch Unexpected Bugs Mocky Tests Can Become Closely Tied to Implementation But All These Problems Can Be Overcome

Synthesis: What Do We Want from Our Tests, Anyway?

Correctness Clean, Maintainable Code Productive Workflow Evaluate Your Tests Against the Benefits You Want from Them

Architectural Solutions

Ports and Adapters/Hexagonal/Clean Architecture Functional Core, Imperative Shell

Conclusion

Obey the Testing Goat!

Testing Is Hard

Keep Your CI Builds Green Take Pride in Your Tests, as You Do in Your Code

Remember to Tip the Bar Staff Don’t Be a Stranger!

A. PythonAnywhere

Running Firefox Selenium Sessions with Xvfb Setting Up Django as a PythonAnywhere Web App Cleaning Up /tmp Screenshots The Deployment Chapter

B. Django Class-Based Views

Class-Based Generic Views The Home Page as a FormView Using form_valid to Customise a CreateView A More Complex View to Handle Both Viewing and Adding to a List

The Tests Guide Us, for a While Until We’re Left with Trial and Error Back on Track Is That Your Final Answer?

Compare Old and New Best Practices for Unit Testing CBGVs?

Take-Home: Having Multiple, Isolated View Tests with Single Assertions Helps

C. Provisioning with Ansible

Installing System Packages and Nginx Configuring Gunicorn, and Using Handlers to Restart Services What to Do Next

Move Deployment out of Fabric and into Ansible Use Vagrant to Spin Up a Local VM

D. Testing Database Migrations

An Attempted Deploy to Staging Running a Test Migration Locally

Entering Problematic Data Copying Test Data from the Live Site Confirming the Error

Inserting a Data Migration

Re-creating the Old Migration

Testing the New Migrations Together Conclusions

E. What to Do Next

Notifications—Both on the Site and by Email Switch to Postgres Run Your Tests Against Different Browsers 404 and 500 Tests The Django Admin Site Investigate a BDD Tool Write Some Security Tests Test for Graceful Degradation Caching and Performance Testing JavaScript MVC Frameworks Async and Websockets Switch to Using py.test Client-Side Encryption Your Suggestion Here

F. Cheat Sheet

Initial Project Setup The Basic TDD Workflow Moving Beyond dev-only Testing General Testing Best Practices Selenium/Functional Testing Best Practices Outside-In, Test Isolation Versus Integrated Tests, and Mocking

G. Bibliography

Index Colophon Copyright

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