Book Image

Test-Driven Python Development

By : Siddharta Govindaraj
Book Image

Test-Driven Python Development

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.
Table of Contents (20 chapters)
Test-Driven Python Development
Credits
About the Author
Acknowledgments
About the Reviewers
www.PacktPub.com
Preface
Index

Arrange-Act-Assert


Let us start with the first requirement. Here is the test:

    def test_stock_update(self):
        """An update should set the price on the stock object
        We will be using the `datetime` module for the timestamp
        """
        goog = Stock("GOOG")
        goog.update(datetime(2014, 2, 12), price=10)
        self.assertEqual(10, goog.price)

Here we call the update method (which doesn't exist yet) with the timestamp and price and then check that the price has been set correctly. We use the assertEqual method provided in the unittest.TestCase class to assert the value.

Since we are using the datetime module to set the timestamp, we will have to add the line from datetime import datetime to the top of the file before it will run.

This test follows the pattern of Arrange-Act-Assert.

  1. Arrange: Set up the context for the test. In this case, we create a Stock object. In other tests, it may involve creating multiple objects or hooking a few things together that will be required...