It's several test cases concatenated together. Each test case is fine.

Also getting this error while trying to submit in Java:
2,6,8,10,3,2,6,8,200,700,1,84,10,4,17,6,8,10,6,12,24,36,2,1,7,17,19,211,7,1,1,1,1,1,44,7,7,7,7,7,7,7,7,expected: 44 but was:1

Agreed, what language were you attempting this on?

Nice one. I would change a few bits to make it more readable (and fix one problem: you can return a pair of primes where the second one is out of the specified range i.e. your test does not pass this test: assertEquals("null", Arrays.toString(GapInPrimes.gap(2, 2, 3)));) but the overall result is really neat.

there seems to be a strange test. I'm getting the error "expected:<-44> but was:<1>" for this iput: "2 ,6 ,8 ,10 ,3 ,2 ,6 ,8 ,200 ,700 ,1 ,84 ,10 ,4 ,17 ,6 ,8 ,10 ,6 ,12 ,24 ,36 ,2 ,1 ,7 ,17 ,19 ,211 ,7 ,1 ,1 ,1 ,1 ,1 ,44 ,7 ,7 ,7 ,7 ,7 ,7 ,7 ,7 ,3 ,3 ,3 ,3 ,3 ,3 ,3 ,3 ,3 ,3 ,3 ,3 ,3 ,3 ,35 ,5 ,5 ,5 ,5 ,5 ,5 ,5 ,5 ,5 ,5 ,7 ,7 ,7 ,7 ,1000 ,2 ,-6 ,8 ,-10 ,-3 ,2 ,6 ,8 ,2 ,-66 ,34 ,-35 ,66 ,700 ,1002 ,-84 ,10 ,4 ,-2147483647 ,-18 ,6 ,-8 ,-10 ,6 ,12 ,-24 ,36 ,-20 ,1 ,7 ,17 ,19 ,211 ,7 ,1 ,1 ,-1 ,1 ,1 ,-44 ,7 ,7 ,7 ,7 ,7 ,7 ,7 ,7"

This input does not comply with the exercise description...