I've found this with the Java solutions as well. A test for Long.MAX_VALUE fails for many of the solutions and the description doesn't specify an upper limit for prod.

    @Test
    public void testMaxLong() {
        long[] r = new long[] {2971215073L, 4807526976L, 0};
        assertArrayEquals(r, ProdFib.productFib(Long.MAX_VALUE /* 9223372036854775807 */));
    }