'Check if CustomKernel works when the input array/list
sums to zero.'

def test_custom_2D_kernel_zerosum(self):

    array = [[0, (-1), 0], [(-1), 4, (-1)], [0, (-1), 0]]
    custom = CustomKernel(array)
    custom.normalize()
    assert (custom.truncation == 0.0)
    assert (custom._kernel_sum == 0.0)
