Added model state test for framer (#152)

tests/FrameCameraTests.cpp

@@ -37,6 +37,14 @@ TEST_P(FramerParameterizedTest, JacobianTest) {
 
 // NOTE: The imagePt format is (Lines,Samples)
 
+TEST_F(FrameSensorModel, State) {
+   std::string modelState = sensorModel->getModelState();
+   EXPECT_NO_THROW(
+         sensorModel->replaceModelState(modelState)
+   );
+   EXPECT_EQ(sensorModel->getModelState(), modelState);
+}
+
 // centered and slightly off-center:
 TEST_F(FrameSensorModel, Center) {
    csm::ImageCoord imagePt(7.5, 7.5);