test: pid: zone

Add unit-tests for the PID zone module.
Add zone_mock.

Tested: Ran on quanta-q71l board and it behaved as expected.

Change-Id: I51185b2d2daacea6ffb687e8f38c4fe2b2a1bed3
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/sensors/manager.hpp b/sensors/manager.hpp
index d37787a..ebf4962 100644
--- a/sensors/manager.hpp
+++ b/sensors/manager.hpp
@@ -46,9 +46,9 @@
             std::unique_ptr<Sensor> sensor);
 
         // TODO(venture): Should implement read/write by name.
-        const std::unique_ptr<Sensor>& getSensor(const std::string& name) const
+        Sensor* getSensor(const std::string& name) const
         {
-            return _sensorMap.at(name);
+            return _sensorMap.at(name).get();
         }
 
         sdbusplus::bus::bus& getPassiveBus(void)