Integration and unit tests in large Grails project | Stack Overflow

Integration and unit tests in large Grails project - Stack Overflow

It is usually more complicated to write unit tests due to having to deal with mock objects than integration tests in a large Grails project. This article even suggests we can even do away with unit tests altogether and write only integration tests which I tend to agree.
The only disadvantage I see is the speed of execution for integration test as compared to same unit test.
What are your thoughts about this from your actual experience working on a large scale Grails project?
If we write a unit test that tests exactly same method and also write integration test that also tests exactly same method, is this normal way of writing tests?
What you ended up with in terms of ratio of unit tests to integrations tests in actual large Grails project?
Have you successfully completed a large Grails project without writing any tests?