Unity Test Tools package will produce an exit code of 2 (partial fail) or 3 (all fail) if there are integration test failures. Currently, the plugin treats 2 and 3 as errors and I am hoping they can be setup to mark the build as unstable or to have it as an option.

The documentation regarding the exit codes of 0, 2, and 3 are available on the 19th page of UnitTestTools>Docs>UnitTestTools-en.pdf.