_("Make sure lazy2 function calling/assignment works"); Cu.import("resource://services-sync/util.js"); function run_test() { let count = 0; let Foo = function() { return ++count; } _("Make a thing instance of Foo but make sure it isn't initialized yet"); let obj = {}; Utils.lazy2(obj, "thing", Foo); do_check_eq(count, 0); _("Access the property to make it evaluates"); do_check_eq(typeof obj.thing, "number"); do_check_eq(count, 1); do_check_eq(obj.thing, 1); _("Additional accesses don't evaluate again (nothing should change"); do_check_eq(typeof obj.thing, "number"); do_check_eq(count, 1); do_check_eq(obj.thing, 1); _("More lazy properties will constrct more"); do_check_eq(typeof obj.other, "undefined"); Utils.lazy2(obj, "other", Foo); do_check_eq(typeof obj.other, "number"); do_check_eq(count, 2); do_check_eq(obj.other, 2); _("Sanity check that the original property didn't change"); do_check_eq(typeof obj.thing, "number"); do_check_eq(count, 2); do_check_eq(obj.thing, 1); }