Unit testing objects with nested properties

I would like to know what is the best approach in order to unit test objects with nested properties.

This is the structure I'm using. ContainerType is a sort of wrapper object. It contains two String properties and an HolderList property. HolderList is an object that contains a list of Holders and so on. The model is like this one because I'm using JAXB in order to generate an XML output.

public class Container
{
    private String code;
    private String description;
    private HolderList holderList;

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public HolderList getHolderList() {
        return holderList;
    }

    public void setHolderList(HolderList holderList) {
        this.holderList = holderList;
    }

    public static class HolderList
    {
        private List<Holder> holders;

        public List<Holder> getHolders() {
            return holders;
        }

        public void setHolders(List<Holder> holders) {
            this.holders = holders;
        }
    }
    public static class Holder
    {
        private String code;
        private GroupList groupList;

        public String getCode() {
            return code;
        }

        public void setCode(String code) {
            this.code = code;
        }

        public GroupList getGroupList() {
            return groupList;
        }

        public void setGroupList(GroupList groupList) {
            this.groupList = groupList;
        }
    }
    public static class GroupList
    {
        private List<Group> groups;

        public List<Group> getGroups() {
            return groups;
        }

        public void setGroups(List<Group> groups) {
            this.groups = groups;
        }
    }
    public static class Group
    {
        private String code;
        private TitleList titleList;

        public TitleList getTitleList() {
            return titleList;
        }

        public void setTitleList(TitleList titleList) {
            this.titleList = titleList;
        }

        public String getCode() {
            return code;
        }

        public void setCode(String code) {
            this.code = code;
        }
    }
    public static class TitleList
    {
        private List<Title> titles;

        public List<Title> getTitles() {
            return titles;
        }

        public void setTitles(List<Title> titles) {
            this.titles = titles;
        }
    }
    public static class Title
    {
        private String code;
        private String description;

        public String getCode() {
            return code;
        }

        public void setCode(String code) {
            this.code = code;
        }

        public String getDescription() {
            return description;
        }

        public void setDescription(String description) {
            this.description = description;
        }
    }
}

My approach would be like this, but I think unit tests will become unreadable. In addition this pattern is not developer friendly.

Container container = operation.getContainer(request);
assertNotNull(container);
assertEquals("0", container.getOutcomeCode());
assertEquals(1, container.getHolderList().getHolders().size());
assertEquals("123456", container.getHolderList().getHolders().get(0).getCode());
assertEquals(2, container.getHolderList().getHolders().get(0).getGroupList().getGroups().size());
assertEquals("123456", container.getHolderList().getHolders().get(0).getGroupList().getGroups().get(0).getCode());
assertEquals(1, container.getHolderList().getHolders().get(0).getGroupList().getGroups().get(0).getTitleList().getTitles().size());
assertEquals("123456", container.getHolderList().getHolders().get(0).getGroupList().getGroups().get(1).getCode());
assertEquals(7, container.getHolderList().getHolders().get(0).getGroupList().getGroups().get(1).getTitleList().getTitles().size());
// additional asserts here

Do you suggest any other approach?

Update

Within operation.getContainer I'm creating a ContainerType with all nested its nested properties. The marshalling with JAXB is done after this step. So, I would like to test this method in order to verify the method returns the expected object. Does this test make sense?