The existing test cases were created based on understanding the code. Creating good tests that cover every case you care about without understanding the code is not possible.

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epolanski 40 minutes ago | parent [-]

Either the current test suite covers the apis and expected behavior or it does not.

	▲	Rapzid 8 minutes ago \| parent [-]
		These big ports we are hearing about are of projects with hundreds (prob thousands) of unit tests. Not only are the models typically trained with the original code bases in their dataset, but the test suites themselves have project architecture encoded in them..