@Test
public void testExtract() {

    DataBlock A = new DataBlock(100);
    DataBlock B = A.extract(0, -1, 3);
    B.set(1);
    DataBlock C = B.extract(4, -1, 7);
    C.set(-1);
    DataBlock AM = new DataBlock(100).reverse();
    DataBlock BM = AM.extract(0, -1, 3);
    BM.set(1);
    DataBlock CM = BM.extract(4, -1, 7);
    CM.set(-1);
    assertTrue(ReadDataBlock.equals(A, AM, 0));
}