Test-Driven Development with Python : Obey the Testing Goat: Using Django, Selenium, and JavaScript

Getting Django set up using a functional test -- Extending our functional test using the unittest module -- Testing a simple home page with unit tests -- What are we doing with all these tests? (And, refactoring) -- Saving user input : testing the database -- Improving functional tests : ensuring isolation and removing Voodoo sleeps -- Working incrementally -- Prettification : layout and styling, and what to test about it -- Testing deployment using a staging site -- Getting to a production-ready deployment -- Automating deployment with fabric --Splitting our tests into multiple files, and a generic wait helper -- Validation at the database layer -- A simple form -- More advanced forms -- Dipping our toes, very tentatively, into JavaScript -- Deploying our new code -- User authentication, spiking, and de-spiking -- Using mocks to test external dependencies or reduce duplication -- Test fixtures and a decorator for explicit waits -- Server-side debugging -- Finishing "my lists" : outside-in TDD -- Test isolation, and "listening to your tests" -- Continuous integration (CI) -- The token social bit, the page pattern, and an exercise for the reader -- Fast tests, slow tests, and hot lava -- Obey the testing goat! -- Appendix A: PythonAnywhere -- Appendix B: Django class-based views -- Appendix C: Provisioning with ansible -- Appendix D: Testing database migrations -- Appendix E: Behaviour-driven development (BDD) -- Appendix F: Building a REST API : JSON, Ajax, and mocking with JavaScript -- Appendix G : Django-rest-framework -- Appendix H : Cheat sheet -- Appendix I : What to do ndext -- Appendix J : Source code examples. Copyright Table of Contents Preface Why I Wrote a Book About Test-Driven Development Aims of This Book Outline Conventions Used in This Book Submitting Errata Using Code Examples O’Reilly Safari Contacting O’Reilly Prerequisites and Assumptions Python 3 and Programming How HTML Works Django JavaScript Required Software Installations Git’s Default Editor, and Other Basic Git Config Installing Firefox and Geckodriver Setting Up Your Virtualenv Activating and Deactivating the Virtualenv Installing Django and Selenium Some Error Messages You’re Likely to See When You Inevitably Fail to Activate Your Virtualenv Companion Video Acknowledgments Additional Thanks for the Second Edition Part I. The Basics of TDD and Django Chapter 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 Chapter 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 Commit Chapter 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 Chapter 4. What Are We Doing with All These Tests? (And, Refactoring) 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 The Django Test Client On Refactoring A Little More of Our Front Page Recap: The TDD Process Chapter 5. Saving User Input: Testing the Database 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 Recap Chapter 6. Improving Functional Tests: Ensuring Isolation and Removing Voodoo Sleeps Ensuring Test Isolation in Functional Tests Running Just the Unit Tests Aside: Upgrading Selenium and Geckodriver On Implicit and Explicit Waits, and Voodoo time.sleeps Chapter 7. Working Incrementally Small Design When Necessary Not Big Design Up Front YAGNI! REST (ish) Implementing the New Design Incrementally Using TDD Ensuring We Have a Regression Test Iterating Towards the New Design Taking a First, Self-Contained Step: One New URL A New URL A New View Function Green? Refactor Another Small Step: A Separate Template for Viewing Lists A Third Small Step: A URL 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 A Regression! Pointing Our Forms at the New URL Biting the Bullet: 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 The Functional Tests Detect Another Regression One More View to Handle Adding Items to an Existing List Beware of Greedy Regular Expressions! The Last New URL The Last New View Testing the Response Context Objects Directly A Final Refactor Using URL includes Part II. Web Development Sine Qua Nons Chapter 8. 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 StaticLiveServerTestCase 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 Chapter 9. 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 Installing Python 3.6 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 Manually, and Using requirements.txt Simple Nginx Configuration Creating the Database with migrate Success! Our Hack Deployment Works Chapter 10. 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 Systemd to Make Sure Gunicorn Starts on Boot Saving Our Changes: Adding Gunicorn to Our requirements.txt Thinking About Automating Saving Templates for Our Provisioning Config Files Saving Our Progress Chapter 11. Automating Deployment with Fabric Breakdown of a Fabric Script for Our Deployment Creating the Directory Structure Pulling Down Our Source Code with Git Updating settings.py Updating the Virtualenv Migrating the Database If Necessary Trying It Out Deploying to Live Nginx and Gunicorn Config Using sed Git Tag the Release Further Reading Chapter 12. Splitting Our Tests into Multiple Files, and a Generic Wait Helper Start on a Validation FT: Preventing Blank Items Skipping a Test Splitting Functional Tests Out into Many Files Running a Single Test File A New Functional Test Tool: A Generic Explicit Wait Helper Finishing Off the FT Refactoring Unit Tests into Several Files Chapter 13. Validation at the Database Layer Model-Layer Validation The self.assertRaises Context Manager A Django Quirk: Model Save Doesn’t Run Validation Surfacing Model Validation Errors in the View Checking That 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 Chapter 14. 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 An Unexpected Benefit: Free Client-Side Validation from HTML5 A Pat on the Back But Have We Wasted a Lot of Time? Using the Form’s Own Save Method Chapter 15. 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 Wrapping Up: What We’ve Learned About Testing Django Chapter 16. 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 Fixtures, Execution Order, and Global State: Key Challenges of JS Testing console.log for Debug Printing Using an Initialize Function for More Control Over Execution Time Columbo Says: Onload Boilerplate and Namespacing JavaScript Testing in the TDD Cycle A Few Things That Didn’t Make It Chapter 17. Deploying Our New Code Staging Deploy Live Deploy What to Do If You See a Database Error Wrap-Up: git tag the New Release Part III. More Advanced Topics in Testing Chapter 18. User Authentication, Spiking, and De-Spiking Passwordless Auth Exploratory Coding, aka “Spiking” Starting a Branch for the Spike Frontend Log in UI Sending Emails from Django Using Environment Variables to Avoid Secrets in Source Code Storing Tokens in the Database Custom Authentication Models Finishing the Custom Django Auth De-spiking Reverting Our Spiked Code A Minimal Custom User Model Tests as Documentation A Token Model to Link Emails with a Unique ID Chapter 19. Using Mocks to Test External Dependencies or Reduce Duplication Before We Start: Getting the Basic Plumbing In Mocking Manually, aka Monkeypatching The Python Mock Library Using unittest.patch Getting the FT a Little Further Along Testing the Django Messages Framework Adding Messages to Our HTML Starting on the Login URL Checking That We Send the User a Link with a Token De-spiking Our Custom Authentication Backend 1 if = 1 More Test The get_user Method Using Our Auth Backend in the Login View An Alternative Reason to Use Mocks: Reducing Duplication Using mock.return_value Patching at the Class Level The Moment of Truth: Will the FT Pass? It Works in Theory! Does It Work in Practice? Finishing Off Our FT, Testing Logout Chapter 20. Test Fixtures and a Decorator for Explicit Waits Skipping the Login Process by Pre-creating a Session Checking That It Works Our Final Explicit Wait Helper: A Wait Decorator Chapter 21. Server-Side Debugging The Proof Is in the Pudding: Using Staging to Catch Final Bugs Setting Up Logging Setting Secret Environment Variables on the Server Adapting Our FT to Be Able to Test Real Emails via POP3 Managing the Test Database on Staging A Django Management Command to Create Sessions Getting the FT to Run the Management Command on the Server Using Fabric Directly from Python Recap: Creating Sessions Locally Versus Staging Baking In Our Logging Code Wrap-Up Chapter 22. 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 Chapter 23. 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! Chapter 24. Continuous Integration (CI) Installing Jenkins Configuring Jenkins Initial Unlock Suggested Plugins for Now Configuring the Admin User Adding Plugins Telling Jenkins Where to Find Python 3 and Xvfb Finishing Off with HTTPS Setting Up Our Project First Build! Setting Up a Virtual Display So the FTs Can Run Headless Taking Screenshots If in Doubt, Try Bumping the Timeout! 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 Chapter 25. The Token Social Bit, the Page Pattern, and an Exercise for the Reader An FT with Multiple Users, and addCleanup The Page Pattern Extend the FT to a Second User, and the “My Lists” Page An Exercise for the Reader Chapter 26. 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 Further Reading 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! Appendix A. PythonAnywhere Running Firefox Selenium Sessions with Xvfb Setting Up Django as a PythonAnywhere Web App Cleaning Up /tmp Screenshots The Deployment Chapter Appendix 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 Appendix 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 Appendix 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 Appendix E. Behaviour-Driven Development (BDD) What Is BDD? Basic Housekeeping Writing an FT as a “Feature” Using Gherkin Syntax As-a /I want to/So that Given/When/Then Not Always a Perfect Fit! Coding the Step Functions Generating Placeholder Steps First Step Definition setUp and tearDown Equivalents in environment.py Another Run Capturing Parameters in Steps Comparing the Inline-Style FT BDD Encourages Structured Test Code The Page Pattern as an Alternative BDD Might Be Less Expressive than Inline Comments Will Nonprogrammers Write Tests? Some Tentative Conclusions Appendix F. Building a REST API: JSON, Ajax, and Mocking with JavaScript Our Approach for This Appendix Choosing Our Test Approach Basic Piping Actually Responding with Something Adding POST Testing the Client-Side Ajax with Sinon.js Sinon and Testing the Asynchronous Part of Ajax Wiring It All Up in the Template to See If It Really Works Implementing Ajax POST, Including the CSRF Token Mocking in JavaScript Finishing the Refactor: Getting the Tests to Match the Code Data Validation: An Exercise for the Reader? Appendix G. Django-Rest-Framework Installation Serializers (Well, ModelSerializers, Really) Viewsets (Well, ModelViewsets, Really) and Routers A Different URL for POST Item Adapting the Client Side What Django-Rest-Framework Gives You Configuration Instead of Code Free Functionality Appendix H. 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 Appendix I. 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 Write Some Security Tests Test for Graceful Degradation Caching and Performance Testing JavaScript MVC Frameworks Async and Websockets Switch to Using py.test Check Out coverage.py Client-Side Encryption Your Suggestion Here Appendix J. Source Code Examples Full List of Links for Each Chapter Using Git to Check Your Progress Downloading a ZIP File for a Chapter Don’t Let it Become a Crutch! Bibliography Index About the Author Colophon By Taking You Through The Development Of A Real Web Application From Beginning To End, The Second Edition Of This Hands-on Guide Demonstrates The Practical Advantages Of Test-driven Development (tdd) With Python. You'll Learn How To Write And Run Tests Before Building Each Part Of Your App, And Then Develop The Minimum Amount Of Code Required To Pass Those Tests. The Result? Clean Code That Works. In The Process, You'll Learn The Basics Of Django, Selenium, Git, Jquery, And Mock, Along With Current Web Development Techniques. If You're Ready To Take Your Python Skills To The Next Level, This Book--updated For Python 3.6--clearly Demonstrates How Tdd Encourages Simple Designs And Inspires Confidence. Dive Into The Tdd Workflow, Including The Unit Test/code Cycle And Refactoring Use Unit Tests For Classes And Functions, And Functional Tests For User Interactions Within The Browser Learn When And How To Use Mock Objects, And The Pros And Cons Of Isolated Vs. Integrated Tests Test And Automate Your Deployments With A Staging Server Apply Tests To The Third-party Plugins You Integrate Into Your Site Run Tests Automatically By Using A Continuous Integration Environment Use Tdd To Build A Rest Api With A Front-end Ajax Interface By taking you through the development of a real web application from beginning to end, the updated second edition of this hands-on guide demonstrates the practical advantages of test-driven development (TDD) with Python. You’ll learn how to write and run tests before building each part of your app, and then develop the minimum amount of code required to pass those tests. The result? Clean code that works. Author Harry J.W. Percival uses a concrete example—the development of a web site, from scratch—to teach TDD methodology and how it applies to web programming, from the basics of database integration and Javascript to more advanced topics such as mocking, Ajax, and REST APIs. It's ideal for relative newcomers and self-taught web developers looking to take their skills to the next level with a more structured approach. Printing History August 2017: Second Edition 2017-08-02: First Release 2018-03-02: Second Release