@Test
public void neighboursInBlockForSingleBonds() {

    String acpString = "C0C1C2C3 0:1(1),0:3(1),1:2(1),2:3(1)";
    IAtomContainer ac = AtomContainerPrinter.fromString(acpString, builder);
    AtomRefinable refinable = new AtomRefinable(ac);
    
    Invariant invariant = refinable.neighboursInBlock(set(0, 2), 1);
    assertTrue(invariant instanceof IntegerInvariant);
    assertEquals(new IntegerInvariant(2), invariant);
}