autotest: add autotest for invalid battery backend checks

Tools/autotest/rover.py

@@ -6845,6 +6845,37 @@ def met(self, m):
             if len(requirements) == 0 and low_sats_seen and seen_bad_loc:
                 break
 
+    def BatteryInvalid(self):
+        '''check Battery prearms report useful data to user'''
+        self.start_subtest("Changing battery types makes no difference")
+        self.set_parameter("BATT_MONITOR", 0)
+        self.assert_prearm_failure("Battery 1 unhealthy", other_prearm_failures_fatal=False)
+        self.set_parameter("BATT_MONITOR", 4)
+        self.wait_ready_to_arm()
+
+        self.start_subtest("No battery monitor should be armable")
+        self.set_parameter("BATT_MONITOR", 0)
+        self.reboot_sitl()
+        self.wait_ready_to_arm()
+
+        self.set_parameter("BATT_MONITOR", 4)
+        self.assert_prearm_failure("Battery 1 unhealthy", other_prearm_failures_fatal=False)
+        self.reboot_sitl()
+        self.wait_ready_to_arm()
+
+        self.start_subtest("Invalid backend should have a clear error")
+        self.set_parameter("BATT_MONITOR", 98)
+        self.reboot_sitl()
+        self.assert_prearm_failure("Battery 1 unhealthy", other_prearm_failures_fatal=False)
+
+        self.start_subtest("Switching from an invalid backend to a valid backend should require a reboot")
+        self.set_parameter("BATT_MONITOR", 4)
+        self.assert_prearm_failure("Battery 1 unhealthy", other_prearm_failures_fatal=False)
+
+        self.start_subtest("Switching to None should NOT require a reboot")
+        self.set_parameter("BATT_MONITOR", 0)
+        self.wait_ready_to_arm()
+
     def tests(self):
         '''return list of all tests'''
         ret = super(AutoTestRover, self).tests()
@@ -6941,6 +6972,7 @@ def tests(self):
             self.RCDuplicateOptionsExist,
             self.ClearMission,
             self.JammingSimulation,
+            self.BatteryInvalid,
         ])
         return ret