@Test
public void getConnectivity() {

    String acpString = "C0C1C2C3 0:1(1),1:2(2),2:3(3)";
    IAtomContainer ac = AtomContainerPrinter.fromString(acpString, builder);
    AtomRefinable refinable = new AtomRefinable(ac);
    assertEquals(1, refinable.getConnectivity(0, 1));
    assertEquals(2, refinable.getConnectivity(1, 2));
    assertEquals(3, refinable.getConnectivity(2, 3));
}