autotest: add test for mot_pwm validation

Tools/autotest/arducopter.py

@@ -4280,6 +4280,28 @@ class AutoTestCopter(AutoTest):
             self.customise_SITL_commandline(command_line_args)
             self.fly_rangefinder_drivers_fly([x[0] for x in do_drivers])
 
+    def test_parameter_validation(self):
+        self.progress("invalid; min must be less than max:")
+        self.set_parameter("MOT_PWM_MIN", 100)
+        self.set_parameter("MOT_PWM_MAX", 50)
+        self.drain_mav()
+        self.assert_prearm_failure("Check MOT_PWM_MIN/MAX")
+        self.progress("invalid; min must be less than max (equal case):")
+        self.set_parameter("MOT_PWM_MIN", 100)
+        self.set_parameter("MOT_PWM_MAX", 100)
+        self.drain_mav()
+        self.assert_prearm_failure("Check MOT_PWM_MIN/MAX")
+        self.progress("invalid; both must be non-zero or both zero (min=0)")
+        self.set_parameter("MOT_PWM_MIN", 0)
+        self.set_parameter("MOT_PWM_MAX", 100)
+        self.drain_mav()
+        self.assert_prearm_failure("Check MOT_PWM_MIN/MAX")
+        self.progress("invalid; both must be non-zero or both zero (max=0)")
+        self.set_parameter("MOT_PWM_MIN", 100)
+        self.set_parameter("MOT_PWM_MAX", 0)
+        self.drain_mav()
+        self.assert_prearm_failure("Check MOT_PWM_MIN/MAX")
+
     def tests(self):
         '''return list of all tests'''
         ret = super(AutoTestCopter, self).tests()
@@ -4506,6 +4528,10 @@ class AutoTestCopter(AutoTest):
              "Fly motor vibration test",
              self.fly_motor_vibration),
 
+            ("ParameterValidation",
+             "Test parameters are checked for validity",
+             self.test_parameter_validation),
+
             ("LogDownLoad",
              "Log download",
              lambda: self.log_download(