sc = new Scenario();
sc.fixtures.add(vf);
ExecutionTrace ex = new ExecutionTrace();
sc.fixtures.add(ex);
sc.insertBetween(null, vf2);
assertEquals(0, sc.fixtures.indexOf(vf));
assertEquals(1, sc.fixtures.indexOf(vf2));
assertEquals(2, sc.fixtures.indexOf(ex));
assertEquals(3, sc.fixtures.size());
sc.insertBetween(ex, vf3);
assertEquals(4, sc.fixtures.size());
assertEquals(0, sc.fixtures.indexOf(vf));
assertEquals(1, sc.fixtures.indexOf(vf2));
assertEquals(2, sc.fixtures.indexOf(ex));
assertEquals(3, sc.fixtures.indexOf(vf3));
ExecutionTrace ex2 = new ExecutionTrace();
sc.fixtures.add(ex2);
sc.insertBetween(ex, vf4);
assertEquals(6, sc.fixtures.size());
assertEquals(0, sc.fixtures.indexOf(vf));
assertEquals(1, sc.fixtures.indexOf(vf2));