Add testcases for mock service

Problem: There are no testcases provided for the mock service. The testcases are suppose to be property based.

Propose solution: Create testcases that are property based.

Additional context: Hypothesis is provided as a framework to use, https://hypothesis.readthedocs.io/en/latest/

Start by locating the mock service and the repository's existing test layout; no specific files or entry points are named in the issue. Read the Hypothesis documentation and inspect the service behavior, then add property-based test cases whose coverage demonstrates the mock service behaves correctly.

Written by the indexing model from the issue text.