PragPub 2011-06: Issue #24 by The Pragmatic Bookshelf

Author:The Pragmatic Bookshelf
Language: eng
Format: epub, mobi
Tags: PragPub—Monthly Magazine
Publisher: The Pragmatic Bookshelf, LLC
Published: 2011-06-01T04:00:00+00:00

Caching, an Example of Caring about Implementation Details

Object oriented programming is all about encapsulation and information hiding. Conventional wisdom suggests that you shouldn’t care about the details. I wholeheartedly agree with this as a general rule of thumb. But experience has shown that sometimes you do care.

Consider the caching library example from the opening paragraphs of this article. I knew how I wanted the cache to work, but I needed a way to verify that it was working properly. Without mocks, this would have been difficult.

Here’s the RSpec example for the case we’ve been talking about:

class ScoreboardPresenter < CachingPresenter

presents :scoreboard

end

describe CachingPresenter do

describe "delegating method calls to the object being presented" do

it "caches implicitly delegated methods" do

scoreboard = mock("scoreboard")

presenter = ScoreboardPresenter.new :scoreboard => scoreboard

scoreboard.should_receive(:results).at_most(1).times

presenter.results

presenter.results

end

end

end

This example is short, concise, and clear. Heck, it’s readable! There was no need to involve file systems, databases, or any other external resource. A mock was all we needed.

More often than not you won’t care about the implementation details; you’ll care about the behavior. In situations where caring about an implementation detail helps drive and verify the behavior, mocks can be a great tool. This caching illustration is an example of that.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.