6. Maintaining Your Test Suite | Test Driven Python Development

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Test Driven Python Development

By : Siddharta Govindaraj

4.4 (5)

Test Driven Python Development

4.4 (5)

By: Siddharta Govindaraj

Overview of this book

This book starts with a look at the test-driven development process, and how it is different from the traditional way of writing code. All the concepts are presented in the context of a real application that is developed in a step-by-step manner over the course of the book. While exploring the common types of smelly code, we will go back into our example project and clean up the smells that we find. Additionally, we will use mocking to implement the parts of our example project that depend on other systems. Towards the end of the book, we'll take a look at the most common patterns and anti-patterns associated with test-driven development, including integration of test results into the development process.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Free Chapter

1. Getting Started with Test-Driven Development

1. Getting Started with Test-Driven Development

Prerequisites

Understanding test-driven development

Using TDD to build a stock alert application

Reorganizing the test code

Summary

2. Red-Green-Refactor – The TDD Cycle

2. Red-Green-Refactor – The TDD Cycle

Tests are executable requirements

Arrange-Act-Assert

Documenting our tests

Testing for exceptions

Exploring assert methods

Specific asserts versus generic asserts

Setup and teardown

Brittle tests

Refactoring the design

Refactoring tests

Exploring the Rule classes

Exercise

Summary

3. Code Smells and Refactoring

3. Code Smells and Refactoring

A dual crossover moving average

Implementing the dual crossover moving average

Identifying code smells

Refactoring

The importance of tests

Exercise

Wrapping up

Summary

4. Using Mock Objects to Test Interactions

4. Using Mock Objects to Test Interactions

Hand writing a simple mock

Using the Python mocking framework

Tying it all together

Summary

5. Working with Legacy Code

5. Working with Legacy Code

What is legacy code?

Understanding the code

Techniques to break dependencies

The cycle continues

Time to refactor

Summary

6. Maintaining Your Test Suite

6. Maintaining Your Test Suite

Goals of test maintenance

Organizing tests

Making tests readable

Writing tests closer to the domain

Summary

7. Executable Documentation with doctest

7. Executable Documentation with doctest

Our first doctest

Test failures

Testing for exceptions

Package-level doctests

Maintaining doctests

Limitations of doctest

How do doctests fit into the TDD process?

Summary

8. Extending unittest with nose2

8. Extending unittest with nose2

Getting started with nose2

Writing tests for nose2

nose2 plugins

Summary

9. Unit Testing Patterns

9. Unit Testing Patterns

Pattern – fast tests

Pattern – running a subset of tests

Pattern – using attributes

Pattern – expected failures

Pattern – data-driven tests

Pattern – integration and system tests

Pattern – spies

Summary

10. Tools to Improve Test-Driven Development

10. Tools to Improve Test-Driven Development

TDD tools

Integrating with build tools

Integrating with packaging tools

Distutils

Integrating with continuous integration tools

Other tools

IDE integration

Summary

A. Answers to Exercises

A. Answers to Exercises

Red-Green-Refactor – The TDD Cycle

Code Smells and Refactoring

B. Working with Older Python Versions

B. Working with Older Python Versions

Writing code that is compatible across versions

Running tests from the command line

Running the examples in this book

Index

Index

Organizing tests

The first step in easing test maintenance is to have a systematic way of organizing tests. When we are implementing a new feature, we need to be able to quickly and easily locate the existing test code for a given method or class. There are three steps to making this easy. We have to decide:

Where the files are stored on the filesystem
What the files are called
The names of the test classes

Filesystem layout

The main consideration in deciding where to place our test code is the ease with which we can locate the tests for a specific class or module. Apart from this, there are two other considerations to keep in mind:

How will this module be packaged and distributed?
How will this code be put into production?

For the first consideration, we have to keep in mind that we will want to distribute unit tests along with the main code. For code that goes into production, we might not always want tests to be deployed, so we would be looking at a way to separate the code and tests.

Given all...

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