@Test public void adjacent() {

    Graph g = new Graph(5);
    g.addAtom(mock(Atom.class));
    g.addAtom(mock(Atom.class));
    g.addAtom(mock(Atom.class));
    g.addEdge(new Edge(0, 1, Bond.IMPLICIT));
    g.addEdge(new Edge(1, 2, Bond.IMPLICIT));
    assertTrue(g.adjacent(0, 1));
    assertTrue(g.adjacent(1, 2));
    assertFalse(g.adjacent(0, 2));
}