Integration tests are meant to exercise your external dependencies, ie. Make sure that the external API you depend on still replies that 2+2=4 as it did before.

Integration tests are meant to exercise your external dependencies, ie. Make sure that the external API you depend on still replies that 2+2=4 as it did before. Unit tests prove that your own code is behaving consistently, and integration tests prove that your external dependencies are still behaving the same too ... The point is to assure that nothing unexpected changed, it's not a direct measurement of the quality of the design.