Fix unit testing failing issue

[janithlahirukariyawasam]

Purpose

The purpose of this PR is to fix #91

Goals

Goal is to fix unit testing failing issue.

Approach

Screenshots

Checklist

• [x] This PR doesn't commit any keys, passwords, tokens, usernames, or other secrets.
• [x] I have read and understood the development best practices guidelines ( http://bit.ly/sef-best-practices )
• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation

Related PRs

## Test environment ## Learning

[janithlahirukariyawasam]

@anjula-sack fixed the unit test failing issue.

1. Removed all existing test cases.
2. Wrote unit tests for the service layer instead of routes.
3. Used mocked repositories instead of real database.