@Test public void testOrder() {

    Graph g = new Graph(5);
    assertThat(g.order(), is(0));
    g.addAtom(mock(Atom.class));
    assertThat(g.order(), is(1));
    g.addAtom(mock(Atom.class));
    assertThat(g.order(), is(2));
    g.addAtom(mock(Atom.class));
    assertThat(g.order(), is(3));
    g.addAtom(mock(Atom.class));
    assertThat(g.order(), is(4));
    g.addAtom(mock(Atom.class));
    assertThat(g.order(), is(5));
}