@Test
public void strictIsotopes() throws CDKException {

    SmilesParser smipar = new SmilesParser(SilentChemObjectBuilder.getInstance());
    IAtomContainer mol = smipar.parseSmiles("[12CH3]C");
    assertThat(new SmilesGenerator(SmiFlavor.AtomicMassStrict).create(mol), is("[12CH3]C"));
}