The next wanker who copy-pastes instead of properly reusing existing code will be tarred and feathered.

Coworker pushed some changes and gave me good reason to rant.
Here's my story:
I start implementing a new feature, senior reviews it and suggest some changes, which are actually good ideas. I continue developing and implement the suggested changes.
The next day, senior keeps working on outdated source and makes similar changes like i did on the day before. Just pushes it anyway and breaks fucking everything.
The api now contains redundant information.
My classes still exist, but aren't used anymore. Let's keep some redundant code in the project, because deleting it is so much work.
All the unit tests broke, but he just commented them out, so everything is green again. We have now 0 tests which actually do something in the project, but at least the build is green...