Unit testing handling of degraded network stack, file corruption, and other imperfections

Question

I\'m primarily a C++ coder, and thus far, have managed without really writing tests for all of my code. I\'ve decided this is a Bad Idea(tm), after adding new features that subt

Answer 1

what sort of tests would you write to constantly check those sites live?

UnitTests target small sections of code you write. UnitTests do not confirm that things are ok in the world. You should instead define application behavior for those imperfect scenarios. Then you can UnitTest your application in those imperfect scenarios.

for instance a crawler

A crawler is a large body of code you might write. It has some different parts, one part might fetch a webpage. Another part might analyze html. Even these parts may be too large to write a unit test against.

How do you test an application will do its job in the face of a degraded network stack? The developer tests it personally by purposely setting up a gateway that drops packets to simulate a bad network when he first writes it.

If a test uses the network, it's not a UnitTest.

A UnitTest (which must target your code) cannot call the network. You didn't write the network. The UnitTest should involve a mock network with simulated (but consistent each time) packet loss.

Unit tests seem to test the code only in perfect conditions

UnitTests test your code in defined conditions. If you're only capable of defining perfect conditions, your statement is true. If you're capable of defining imperfect conditions, your statement is false.