Comment by mort96

So, I very much agree with mike_hearn, their description of how glibc is backwards compatible in theory due to symbol versioning matches my understanding of how glibc works, and their lack of care to test if glibc stays backwards compatible in practice seems evident. They certainly don't seem to do automated UI tests against a suite of representative precompiled binaries to ensure compatibility.

However, I don't understand where unit testing comes in. Testing that whole applications keep working with new glibc versions sounds a lot like integration testing. What's the "unit" that's being tested when ensuring that the software on top of glibc doesn't break?