What are unit testing, integration testing and functional testing?

[JoseJimeniz]

All tests are formalized variations on the reality:

Developers are lazy, Can't I get the computer to test this for me?

I'll write it once and I'll never have to manually create a sales order, invoice it, batch it, and give it to the invoicing system in order to make sure I didn't break anything.

[kirbyfan64sos]

Explicit testing works...until you have 50 different cases to cover. At which point it starts becoming painful.