NIH is amazing as long as you are realistic about what you are taking ownership of.
For example, the cost of maintaining a bespoke web frontend "framework" that is specific to your problem domain is probably justifiable in many cases.
The same cannot be said for databases, game engines, web servers, cryptographic primitives, etc. If you have a problem so hard that no existing RDBMS or engine can support, you should seriously question the practicality of solving your problem at all. There's probably some theoretical constraint or view of the problem space you haven't discovered yet. Reorganizing the problem is a lot cheaper than reinventing the entire SQLite test suite from zero.
For example, the cost of maintaining a bespoke web frontend "framework" that is specific to your problem domain is probably justifiable in many cases.
The same cannot be said for databases, game engines, web servers, cryptographic primitives, etc. If you have a problem so hard that no existing RDBMS or engine can support, you should seriously question the practicality of solving your problem at all. There's probably some theoretical constraint or view of the problem space you haven't discovered yet. Reorganizing the problem is a lot cheaper than reinventing the entire SQLite test suite from zero.