added support for onChange report

Report is now notified when metric changes and updates reading values.

Tested:
  - Added new unit tests
  - OnChange report updates Readings when metric values changes

Change-Id: I3be9ef7aa0486cb15bac627aa1de5cc632613b3b
Signed-off-by: Krzysztof Grobelny <krzysztof.grobelny@intel.com>
diff --git a/tests/src/test_sensor.cpp b/tests/src/test_sensor.cpp
index c073ee7..8738bde 100644
--- a/tests/src/test_sensor.cpp
+++ b/tests/src/test_sensor.cpp
@@ -147,12 +147,9 @@
     ASSERT_TRUE(DbusEnvironment::waitForFuture("notify"));
 }
 
-TEST_F(TestSensorNotification, notifiesListenerWithValueWhenNoChangeOccurs)
+TEST_F(TestSensorNotification, doesntNotifyListenerWhenNoChangeOccurs)
 {
-    InSequence seq;
-
-    EXPECT_CALL(*listenerMock, sensorUpdated(Ref(*sut), Ge(timestamp), 42.7));
-    EXPECT_CALL(*listenerMock, sensorUpdated(Ref(*sut), Ge(timestamp)))
+    EXPECT_CALL(*listenerMock, sensorUpdated(Ref(*sut), Ge(timestamp), 42.7))
         .WillOnce(InvokeWithoutArgs(DbusEnvironment::setPromise("notify")));
 
     sensorObject->setValue(42.7);