What I learned today

I did not exactly learn this today, but I am sharing it as I have found it extremely useful when unit testing code that depends on environment or system property settings. While I am using Java as an example, the general concepts apply any where. Problem : You have a piece of code you are unit testing that uses settings from env variables or system properties passed to the VM (System.getProperty), but you don't want the tests to be affected by the 'real' environment or system properties in the VM. So, your unit tests should not get different results or fail when the real environment changes. Solution : There are several. But the most straightforward is to use a mocking library to mock out the environment or fake it out, whatever your prefer. You can create a fake using a library like EasyMock, PowerMock etc. This I won't discuss in this post, since there are numerous articles for that. Or you can write a simple class that acts as a proxy, using the proxy pattern