Google's internal code management system won't let you check in code that fails pre-checkin tests. This is generally a 'best practice' sort of approach. The challenge is however if you modify a library, and in the process of modifying it you change a side effect, and other code's unit tests fail because they depended on the side effect, you have some choices:
1) You can go fix their code so that they don't have the dependency and then check-in (this can be laborious because they have to approve your changes to their code)
2) You can re-introduce the side effect so that their code continues to work.
3) You can try to get them to change their code (very hard since they probably have bunch of other things going on that don't depend on you)
4) You can create a new library (or routine in the library) that has the semantics you want and deprecate the older version.
While this was extremely painful for folks who were working lower down in the system it was not as big an issue for folks on the upper levels. And in a perverse way it motivated good interface design.
Google's internal code management system won't let you check in code that fails pre-checkin tests. This is generally a 'best practice' sort of approach. The challenge is however if you modify a library, and in the process of modifying it you change a side effect, and other code's unit tests fail because they depended on the side effect, you have some choices:
1) You can go fix their code so that they don't have the dependency and then check-in (this can be laborious because they have to approve your changes to their code)
2) You can re-introduce the side effect so that their code continues to work.
3) You can try to get them to change their code (very hard since they probably have bunch of other things going on that don't depend on you)
4) You can create a new library (or routine in the library) that has the semantics you want and deprecate the older version.
While this was extremely painful for folks who were working lower down in the system it was not as big an issue for folks on the upper levels. And in a perverse way it motivated good interface design.