What are the pros and cons of automated Unit Tests vs automated Integration tests?

Question

Recently we have been adding automated tests to our existing java applications.

What we have

The majority of these tests are integration tes

Answer 1

Joel Spolsky has written very interesting article about unit-testing (it was dialog between Joel and some other guy).

The main idea was that unit tests is very good thing but only if you use them in "limited" quantity. Joel doesn't recommend to achive state when 100% of your code is under testcases.

The problem with unit tests is that when you want to change architecture of your application you'll have to change all corresponding unit tests. And it'll take very much time (maybe even more time than the refactoring itself). And after all that work only few tests will fail.

So, write tests only for code that really can make some troubles.

How I use unit tests: I don't like TDD so I first write code then I test it (using console or browser) just to be sure that this code do nessecary work. And only after that I add "tricky" tests - 50% of them fail after first testing.

It works and it doesn't take much time.