That's a good point. It would be nice if NPM/Microsoft committed to running backwards compatibility tests on packages that had them (for packages that were sig

That's a good point. It would be nice if NPM/Microsoft committed to running backwards compatibility tests on packages that had them (for packages that were significant enough and tests that were efficient enough). This would require a convention that packages indicate in their metadata where the backwards compatibility tests are, and for each package's code to be run against the tests in the previous version of the package (or all previous versions with the same major version number?). A slightly different approach would be for packages to write tests for the specific functionality of their dependencies that they rely on, and NPM could collect that distributed test suite and warn the test writer if a newly published version of one of their dependencies wasn't backwards compatible. NPM could even store such packages in a staging area (for a probationary period) where the dependency solving algorithm of npm wouldn't look by default.