Testing your application

There are many kinds of tests, so many, in fact, that companies often have a dedicated department, called quality assurance (QA), made up of individuals whose job is to test the software the company developers produce.

To start making an initial classification, we can divide tests into two broad categories: white-box and black-box tests.

White-box tests are those that exercise the internals of the code; they inspect it down to a fine level of detail. On the other hand, black-box tests are those that consider the software under test as if within a box, the internals of which are ignored. Even the technology, or the language used inside the box, is not important for black-box tests. What they do is plug some input into one end of the box and verify the output at the other end—that's it.

There is also an in-between category, called gray-box testing, which involves testing a system in the same way we do with the black-box approach, but having some knowledge...