@Test
public void methyleneCyclopropeneTest() {

    IAtomContainer mol = builder.newInstance(IAtomContainer.class);
    AbstractSignatureTest.addCarbons(mol, 4);
    AbstractSignatureTest.addHydrogens(mol, 1, 2);
    AbstractSignatureTest.addHydrogens(mol, 2, 1);
    AbstractSignatureTest.addHydrogens(mol, 3, 1);
    mol.addBond(0, 1, IBond.Order.DOUBLE);
    mol.addBond(0, 2, IBond.Order.SINGLE);
    mol.addBond(0, 3, IBond.Order.SINGLE);
    mol.addBond(2, 3, IBond.Order.DOUBLE);
    MoleculeSignature molSig = new MoleculeSignature(mol);
    String sigFor2Height1 = molSig.signatureStringForVertex(2, 1);
    String sigFor3Height1 = molSig.signatureStringForVertex(3, 1);
    Assert.assertTrue("Height 1 signatures for atoms 2 and 3" + " should be the same",
            sigFor2Height1.equals(sigFor3Height1));
    String sigFor2Height2 = molSig.signatureStringForVertex(2, 1);
    String sigFor3Height2 = molSig.signatureStringForVertex(3, 1);
    Assert.assertTrue("Height 2 signatures for atoms 2 and 3" + " should be the same",
            sigFor2Height2.equals(sigFor3Height2));
}