Tools: autotest: copter: add max alt fence avoidance test

Tools/autotest/arducopter.py

@@ -1604,6 +1604,58 @@ class AutoTestCopter(vehicle_test_suite.TestSuite):
 
         self.zero_throttle()
 
+    # MaxAltFence - fly up and make sure fence action does not trigger
+    # Also check that the vehicle will not try and descend too fast when trying to backup from a max alt fence due to avoidance
+    def MaxAltFenceAvoid(self):
+        '''Test Max Alt Fence Avoidance'''
+        self.takeoff(10, mode="LOITER")
+        """Hold loiter position."""
+
+        # enable fence, only max altitude, defualt is 100m
+        # No action, rely on avoidance to prevent the breach
+        self.set_parameters({
+            "FENCE_ENABLE": 1,
+            "FENCE_TYPE": 1,
+            "FENCE_ACTION": 0,
+        })
+
+        # Try and fly past the fence
+        self.set_rc(3, 1920)
+
+        # Avoid should prevent the vehicle flying past the fence, so the altitude wait should timeouts
+        try:
+            self.wait_altitude(140, 150, timeout=90, relative=True)
+            raise NotAchievedException("Avoid should prevent reaching altitude")
+        except AutoTestTimeoutException:
+            pass
+        except Exception as e:
+            raise e
+
+        # Check descent is not too fast, allow 10% above the configured backup speed
+        max_descent_rate = -self.get_parameter("AVOID_BACKUP_SPD") * 1.1
+
+        def get_climb_rate(mav, m):
+            m_type = m.get_type()
+            if m_type != 'VFR_HUD':
+                return
+            if m.climb < max_descent_rate:
+                raise NotAchievedException("Decending too fast want %f got %f" % (max_descent_rate, m.climb))
+
+        self.context_push()
+        self.install_message_hook_context(get_climb_rate)
+
+        # Reduce fence alt, this will result in a fence breach, but there is no action.
+        # Avoid should then backup the vehicle to be under the new fence alt.
+        self.set_parameters({
+            "FENCE_ALT_MAX": 50,
+        })
+        self.wait_altitude(40, 50, timeout=90, relative=True)
+
+        self.context_pop()
+
+        self.set_rc(3, 1500)
+        self.do_RTL()
+
     # fly_alt_min_fence_test - fly down until you hit the fence floor
     def MinAltFence(self):
         '''Test Min Alt Fence'''
@@ -10318,6 +10370,7 @@ class AutoTestCopter(vehicle_test_suite.TestSuite):
              self.HorizontalFence,
              self.HorizontalAvoidFence,
              self.MaxAltFence,
+             self.MaxAltFenceAvoid,
              self.MinAltFence,
              self.FenceFloorEnabledLanding,
              self.AutoTuneSwitch,