@Test
public void testGet2DCenterOfMass_IAtomContainer() {

    Atom atom1 = new Atom("C");
    atom1.setPoint2d(new Point2d(1, 1));
    atom1.setExactMass(12.0);
    Atom atom2 = new Atom("C");
    atom2.setPoint2d(new Point2d(1, 0));
    atom2.setExactMass(12.0);
    IAtomContainer ac = DefaultChemObjectBuilder.getInstance().newInstance(IAtomContainer.class);
    ac.addAtom(atom1);
    ac.addAtom(atom2);
    Point2d p = GeometryTools.get2DCentreOfMass(ac);
    Assert.assertNotNull(p);
    Assert.assertEquals(p.x, 1.0, .1);
    Assert.assertEquals(p.y, 0.5, .1);
}