Create test script for smart_calculator

[jmeyu]

Description

Created test script for smart calculator to ensure all functions work well.

Fixes #(issue_no)

• [ ] Issue_no: <insert your issue no here>
• [x] Not applicable

Type of change

Choosing one or more options from the following as per the nature of your Pull request.

• [ ] New project insert
• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Documentation Update

Project

• calculator_test

• Created test script for smart calculator to ensure all functions work well.

Checklist:

Please tick all the boxes that are fulfilled by your Pull Request.

• [x] I have named my files and folder, according to this project's guidelines.
• [x] My code follows the style guidelines of this project.
• [x] I have commented on my code, particularly in hard-to-understand areas.
• [x] I have created a helpful and easy to understand README.md, according to the given README_TEMPLATE.
• [x] My changes do not produce any warnings.