public void containerAddNullChildReturnsNull()
    {
      Container container = new Container("chest");
      var item = container.AddChild(null);

      Assert.That(item, Is.Null);
    }
    public void containerHasChildrenReturnsTrueIfChildren()
    {
      Container container = new Container("chest");
      var entity = new Thing("cup");
      var item = container.AddChild(entity);

      Assert.That(container.HasChildren(), Is.True);
    }
    public void containerAddChildReturnsChild()
    {
      Container container = new Container("chest");
      var entity = new Thing("cup");
      var item = container.AddChild(entity);

      Assert.That(item.SameIdentityAs(entity), Is.True);
    }
    public void containerGetChildrenReturnsChildren()
    {
      Container container = new Container("chest");
      var entity = new Thing("cup");
      var item = container.AddChild(entity);

      var children = container.GetChildren();
      Assert.That(children.First().SameIdentityAs(item), Is.True);
    }