John Lakos differs from you. In his book "Large Scale C++ Software Development" he advocates starting at the lowest level of your own code, that is, subroutines that only make system calls or call libraries that are provided by the system.
Then you unit test the second level - subroutines that only call that first level, or that call the system or libraries.
main() sits at the top level.
Not every program is straightforward to levelize. His point is that one should do so.
Also the unit tests for any one level should focus on what is new on that specific level, with the assumption that all the lower levels are flawless. In general they won't really be but when that's the case you write a unit test for the lower level.
This keeps the LOC on the tests about the same as the LOC in the deliverable.
It is unfortunate that his book focusses on C++; really he should have written a separate book on testing that was language-agnostic. There is very little of that section that's really specific to C++.
In addition to unit tests I do integration tests. If there's a file format involved I create lots of input files that contain various edge cases.
Then you unit test the second level - subroutines that only call that first level, or that call the system or libraries.
main() sits at the top level.
Not every program is straightforward to levelize. His point is that one should do so.
Also the unit tests for any one level should focus on what is new on that specific level, with the assumption that all the lower levels are flawless. In general they won't really be but when that's the case you write a unit test for the lower level.
This keeps the LOC on the tests about the same as the LOC in the deliverable.
It is unfortunate that his book focusses on C++; really he should have written a separate book on testing that was language-agnostic. There is very little of that section that's really specific to C++.
In addition to unit tests I do integration tests. If there's a file format involved I create lots of input files that contain various edge cases.