Add unit tests for pkg/model code

**Issue/Feature Description:**
 Add unit tests and achieve coverage >70%

 **Why this issue to fixed / feature is needed(give scenarios or use cases):**
 To imporove code quality and covergae

 **How to reproduce, in case of a bug:**

 **Other Notes /  Environment Information: (Please give the env information, log link or any useful information for this issue)**

