Tests that use random input data are much more difficult to write correctly. Your test needs to know the expected result not just for one case, but for every possible case. That will vastly increase the number of bugs in your test code, leading to a seemingly endless stream of false-positives.
The worst part is that the feedback is late. The test will randomly fail long after it was written. There's a lot of needless overhead in relearning the context of the failing code just so you can fix a test that is not general enough for the data it was provided.
There are ways to effectively use randomly-generated test data, but it's harder than you'd think to do it right.
The worst part is that the feedback is late. The test will randomly fail long after it was written. There's a lot of needless overhead in relearning the context of the failing code just so you can fix a test that is not general enough for the data it was provided.
There are ways to effectively use randomly-generated test data, but it's harder than you'd think to do it right.