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Test Driven Python Development

You're reading from   Test Driven Python Development Develop high-quality and maintainable Python applications using the principles of test-driven development

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Product type Paperback
Published in Apr 2015
Publisher Packt
ISBN-13 9781783987924
Length 264 pages
Edition 1st Edition
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Author (1):
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Siddharta Govindaraj Siddharta Govindaraj
Author Profile Icon Siddharta Govindaraj
Siddharta Govindaraj
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Toc

Table of Contents (14) Chapters Close

Preface 1. Getting Started with Test-Driven Development FREE CHAPTER 2. Red-Green-Refactor – The TDD Cycle 3. Code Smells and Refactoring 4. Using Mock Objects to Test Interactions 5. Working with Legacy Code 6. Maintaining Your Test Suite 7. Executable Documentation with doctest 8. Extending unittest with nose2 9. Unit Testing Patterns 10. Tools to Improve Test-Driven Development A. Answers to Exercises B. Working with Older Python Versions 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...
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