why does sorting error occur?
Or should this kata be solved without using sorting?

    @Test
    public void testClosestLess() {
        int[][] points = {{1,2}};
        int[][] results = ClosestPoints.getTopN(points,3);
        assertEquals(results.length, 1);
    }

The expected:<3> but was:<1> error message is not informative at all.

How should cases where the amount of points wanted is more than the given? Just giving empty coords ({0,0}) doesn't work and this is not indicated in the description.

has now 300 random tests. ;p

Has now one random test case.

Has no random test cases

FYI - Initial description first param name is missing