autotest: add test for EK3_OGN_HGT_MASK bug

Tools/autotest/arducopter.py

@@ -11377,6 +11377,43 @@ class AutoTestCopter(vehicle_test_suite.TestSuite):
         self.disarm_vehicle(force=True)
         self.reboot_sitl()
 
+    def EK3_OGN_HGT_MASK_climbing(self):
+        '''check combination of height bits doesn't cause climb'''
+        self.context_push()
+        self.set_parameters({
+            'EK3_OGN_HGT_MASK': 5,
+        })
+        self.reboot_sitl()
+
+        expected_alt = 10
+
+        self.change_mode('GUIDED')
+        self.wait_ready_to_arm()
+        current_alt = self.get_altitude()
+
+        expected_alt_abs = current_alt + expected_alt
+
+        self.takeoff(expected_alt, mode='GUIDED')
+        self.delay_sim_time(5)
+
+        def check_altitude(mav, m):
+            m_type = m.get_type()
+            epsilon = 10  # in metres
+            if m_type == 'GPS_RAW_INT':
+                got_gps_alt = m.alt * 0.001
+                if abs(expected_alt_abs - got_gps_alt) > epsilon:
+                    raise NotAchievedException(f"Bad GPS altitude (got={got_gps_alt} want={expected_alt_abs})")
+            elif m_type == 'GLOBAL_POSITION_INT':
+                if abs(expected_alt - m.relative_alt * 0.001) > epsilon:
+                    raise NotAchievedException("Bad canonical altitude")
+
+        self.install_message_hook_context(check_altitude)
+
+        self.delay_sim_time(1500)
+
+        self.context_pop()
+        self.reboot_sitl(force=True)
+
     def tests2b(self):  # this block currently around 9.5mins here
         '''return list of all tests'''
         ret = ([
@@ -11461,6 +11498,7 @@ class AutoTestCopter(vehicle_test_suite.TestSuite):
             self.GuidedModeThrust,
             self.CompassMot,
             self.AutoRTL,
+            self.EK3_OGN_HGT_MASK_climbing,
             self.EK3_OGN_HGT_MASK,
             self.FarOrigin,
             self.GuidedForceArm,