@Test public void testGetRangeSum() { int n = 500; long[] A = randomArray(n); FenwickTree fw = fenwickTree(A); for (int i = 0; i < A.length; i++) { for (int j = i; j < A.length; j++) { long sum = rangeSum(A, i, j); assertEquals(sum, fw.getRangeSum(i + 1, j + 1)); } } }