-It should do something sensible, but no particular behavior is
-required. None of the test cases call @func{thread_set_priority} from a
-thread while it is receiving a priority donation.
+It sets the thread's base priority. The thread's effective priority
+becomes the higher of the newly set priority or the highest donated
+priority. When the donations are released, the thread's priority
+becomes the one set through the function call. This behavior is checked
+by the @code{priority-donate-lower} test.