Programmers who incorporate unit testing into their development process inevitably hit what we call the testing wall; this is the point where your code becomes too hard to test in isolation. You've hit the testing wall if you've ever thought:

• "If my code only did simple stuff, unit testing would be easy."
• "I often write tests, but when the test is too hard to write, I skip it."
• "I know my code is hard to test, but I don't know how to change it to make it easier to write unit tests."
• "Forget this! I'm applying for a job at the coffee shop."

In Part 1 of this series, you wrote code and tests for the initial implementation of a Twitter client. The code worked; the tests passed. However, you took a brute force approach when writing the unit tests: Most of the tests depended on the availability of the Twitter service. This resulted in slow tests, and slow tests mean productivity loss. In addition, the testing ignored error paths because the component design didn't lend itself to easily testing what happens when calls to the Twitter service fail.

In Part 2 of this series, you'll refactor the Twitter client code and its tests to create a more robust and easily testable API. You'll do this by applying strategies for decoupling external dependencies from business logic so that those dependencies can be swapped with test-friendly stand-ins (known as mocks) during test execution. In addition, you'll see how components that are easier to test are often easier to use in the context of an application.

Requirements

In order to make the most of this article, you need the following software and files:

ColdFusion 8

• Try
• Buy

MXUnit

• Download

Sample files:

• testdriven_coldfusion_pt2.zip (ZIP, 10K)

Prerequisite knowledge

Working knowledge of ColdFusion Components, some experience writing unit tests for ColdFusion, and knowledge of the concepts covered in Part 1 of this series.

This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported License

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