> There are tools like greenkeeper which use your project's unit test to try out packages before upgrading, adding extra level of assurance.
Some communities have also started doing the reverse, where as a library you can get all your users's tests to run to check that you have not broken something they were using.
I know that that happens for the Rust compiler, possibly some libraries as well. I don't know that it's systematic but I do know that they regularly leverage Cargo to find out major dependencies/users and run those against pending changes.
Some communities have also started doing the reverse, where as a library you can get all your users's tests to run to check that you have not broken something they were using.