### Question:
VFlibMCSHandler extends AbstractMCSAlgorithm implements IMCSBase { @Override public Map<Integer, Integer> getFirstMapping() { return Collections.unmodifiableMap(firstMCS); } VFlibMCSHandler(); @Override void searchMCS(boolean bondTypeMatch); @Override void set(MolHandler reactant, MolHandler product); @Override void set(IQueryAtomContainer source, IAtomContainer target); @Override List<Map<IAtom, IAtom>> getAllAtomMapping(); @Override List<Map<Integer, Integer>> getAllMapping(); @Override Map<IAtom, IAtom> getFirstAtomMapping(); @Override Map<Integer, Integer> getFirstMapping(); boolean isBondMatchFlag(); void setBondMatchFlag(boolean shouldMatchBonds);  }### Answer:
@Test public void testGetFirstMapping() throws InvalidSmilesException { SmilesParser sp = new SmilesParser(DefaultChemObjectBuilder.getInstance()); IAtomContainer target = sp.parseSmiles("C\\C=C/Nc1cccc(c1)N(O)\\C=C\\C\\C=C\\C=C/C"); IAtomContainer queryac = sp.parseSmiles("Nc1ccccc1"); VFlibMCSHandler smsd1 = new VFlibMCSHandler(); MolHandler mol1 = new MolHandler(queryac, true, true); MolHandler mol2 = new MolHandler(target, true, true); smsd1.set(mol1, mol2); smsd1.searchMCS(true); assertNotNull(smsd1.getFirstMapping()); assertEquals(7, smsd1.getFirstMapping().size()); }