creating a tree-like structure in GORM

I am trying to correctly define a tree structure in GORM and having trouble.

i have one domain object:

class Navigation {
    Navigation parent
    List children;
    String name;

    static belongsTo = [parent: Navigation]
    static hasMany = [children: Navigation]

    static constraints = {
        parent(nullable: true);
    }
}

and the test:

void testTree() {
    Navigation root = new Navigation(name:"root");
    Navigation top1 = new Navigation(name:"home");
    Navigation top2 = new Navigation(name:"services");

    root.addToChildren(top1).addToChildren(top2).save(flush: true);

    Navigation s1 = new Navigation(name:"plumbing")
    Navigation s2 = new Navigation(name:"baking")

    top2.addToChildren(s1).ad开发者_StackOverflow中文版dToChildren(s2).save(flush: true);

    Navigation t = Navigation.findByName("root")
    assert t.children.size() == 2
}

if i run this test, i get this error:

org.codehaus.groovy.runtime.InvokerInvocationException: groovy.lang.MissingMethodException: No signature of method: grails.Navigation.addToChildren() is applicable for argument types: (grails.Navigation) values: [grails.Navigation : null]

and if i place the contents of that test into boostrap, i dont get that error, and the application starts up, except the navigation table is empty

what can i do to fix this?

You need to mock the Navigation domain so that you can use the GORM methods in your unit test.

Add this to the top of your test case:

mockDomain(Navigation)