You should see something like this:
<...U-Boot banner...>
- Running 21 driver model tests
+ Running 22 driver model tests
Test: dm_test_autobind
Test: dm_test_autoprobe
Test: dm_test_bus_children
Device 'c-test@0': seq 0 is in use by 'a-test'
Device 'c-test@1': seq 1 is in use by 'd-test'
Test: dm_test_bus_children_funcs
+ Test: dm_test_bus_children_iterators
Test: dm_test_bus_parent_data
Test: dm_test_bus_parent_ops
Test: dm_test_children