I decided I had to write my own Document Object Model implementation because the models available to me just won’t meet my requirements.  That involves writing a lot of code, though, and ensuring that Element nodes, Text nodes, etc. all implement Node properties like firstChild, childNodes, etc., and methods like appendChild() correctly.

To lend a hand, I wrote a little InterfaceChecker library for ensuring that tests on a base class are run on derived classes.  (I know, JavaScript uses prototypes instead of proper classes; I’m using the concept’s meaning here.)  In principle, I need to only do three things:

• Write tests for the Node interface’s methods and properties
• Designate Element as inheriting from Node, and
• Provide some functions to build “typical” instances of Element,

My InterfaceChecker will run the Node tests against the “typical” instances of Element, for example.  It’s not DOM-specific, either:  I can do the same to arbitrary JavaScript constructors, like a theoretical Shape and Circle pairing.

This code is for debugging purposes only; in my opinion, it’s a little extreme to include these tests in a production environment.

Please, let me know what you think!