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
About the Author
About the Reviewers

Hand writing a simple mock

To start with, let us look at the code for the Event class so that we can understand what the tests need to do. The following code is in the file in the source directory:

class Event:
    """A generic class that provides signal/slot functionality"""

    def __init__(self):
        self.listeners = []

    def connect(self, listener):

    def fire(self, *args, **kwargs):
        for listener in self.listeners:
            listener(*args, **kwargs)

The way this code works is fairly simple. Classes that want to get notified of the event should call the connect method and pass a function. This will register the function for the event. Then, when the event is fired using the fire method, all the registered functions will be notified of the event. The following is a walk-through of how this class is used:

>>> def handle_event(num):
...   print("I got number {0}".format(num))
>>> event = Event()