Refactor test code

[havi-kim]

Related Issue

Which issue does this pull request resolve?
#390 Test suite improvements

Description of changes

I respect your codebase. However, I believe maintaining the test code might become challenging in the future. Therefore, I would like to propose some improvements to enhance maintainability.

The main points of the changes are as follows:

Improve Maintainability

• Separate reusable functions
• Separate Test Data
• Enhance readability by applying the AAA pattern

Separate Unit Tests and Integration Tests

• Unit tests should focus on minimal functionality according to the Single Responsibility Principle
• Integration tests should continue to be based on the existing Deployer setup
• Add unit tests for internal functions using inheritance

Additionally, I plan to keep all existing tests while adding some missing tests. I have refactored a few tests as examples. If you find these changes acceptable, I would like to proceed with improving the rest of the tests.

[havi-kim]

I am closing this pull request as I believe the proposed changes may not be necessary at this time. Thanks.