Code should be unambiguous where possible
If a random NullPointer is thrown in a test, I'm starting to investigate if the program is at fault, or if the writer of the test did just miss the fact of a variable possible being null. If someone writes "shouldNotBeNull" the intent is clear. This variable can and should never be null.
This of course assumes people don't just copy & paste a pattern blindly, but use the check where it makes sense and an if-null otherwise.
edit: fix typo
