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- The reliability/correctness of the code is more important than some new cool untested or not mature features.
- The cost of maintenance is more important than the cost of prototyping. For example, it is not desired to use some new libraries to reduce the coding effort a bit.
- Each new library/dependency introduces a cost of learning for any developer within the project.
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- Mainstream library even with limited features, known-issues is better than a new library that covers only a subset of requirements even if supposed to be better approach. For example, JUnit library is the obvious choice.
- Do not leave commented out code in the code base. If you are not certain if the code is correct then ask for review.