Test: Refine annotaion and testcase for poll.

1. Add more detail info to make the purpose and process
of the test cases more clear which include test goal,
test step, input, judging criteria, constraints, etc.,
and these can be seen in our Zephyr documentations.
2. Add some negative test code.

Signed-off-by: YouhuaX Zhu <youhuax.zhu@intel.com>

tests/kernel/poll/src/test_poll.c

@@ -253,13 +253,48 @@ void check_results(struct k_poll_event *events, uint32_t event_type,
 /**
  * @brief Test polling with wait
  *
+ * @ingroup kernel_poll_tests
+ *
  * @details
+ * Test Objective:
  * - Test the poll operation which enables waiting concurrently
  * for one/two/all conditions to be fulfilled.
  * - set a single timeout argument indicating
  * the maximum amount of time a thread shall wait.
  *
- * @ingroup kernel_poll_tests
+ * Testing techniques:
+ * - function and block box testing.
+ * - Interface testing.
+ * - Dynamic analysis and testing.
+ *
+ * Prerequisite Conditions:
+ * - CONFIG_TEST_USERSPACE
+ * - CONFIG_DYNAMIC_OBJECTS
+ * - CONFIG_POLL
+ *
+ * Input Specifications:
+ * - N/A
+ *
+ * Test Procedure:
+ * -# Use FIFO/semaphore/signal object to define poll event.
+ * -# Initialize the FIFO/semaphore/signal object.
+ * -# Create a thread to put FIFO,
+ * give semaphore and raise signal.
+ * -# Check the result when signal is raised,
+ * semaphore is givn and fifo is filled.
+ * -# Check the result when no event is satisfied.
+ * -# Check the result when only semaphore is given.
+ * -# Check the result when only FIFO is filled.
+ * -# Check the result when only signal is raised.
+ *
+ * Expected Test Result:
+ * - FIFO/semaphore/signal events available/waitable in poll.
+ *
+ * Pass/Fail Criteria:
+ * - Successful if check points in test procedure are all passed, otherwise failure.
+ *
+ * Assumptions and Constraints:
+ * - N/A
  *
  * @see k_poll_signal_init(), k_poll()
  */
@@ -284,6 +319,9 @@ void test_poll_wait(void)
 			main_low_prio - 1, K_USER | K_INHERIT_PERMS,
 			K_NO_WAIT);
 
+	rc = k_poll(wait_events, ARRAY_SIZE(wait_events), K_NO_WAIT);
+	zassert_equal(rc, -EAGAIN, "should return EAGAIN with K_NO_WAIT");
+
 	rc = k_poll(wait_events, ARRAY_SIZE(wait_events), K_SECONDS(1));
 
 	k_thread_priority_set(k_current_get(), old_prio);