Tests: test implementation for package builders

[rohansen856]

Description

As discussed in PR #2 , we need to implement unit tests for the builder modules (JavaBinaryBuilder, GoBinaryBuilder, ScriptBuilder) to ensure code quality and catch regressions early.

ref:

• PR feat: added template for java binary builder #2 discussion: feat: added template for java binary builder #2 (comment)
• Related comment: feat: added template for java binary builder #2 (comment)

Proposal:
Implement a comprehensive test suite that:

• Uses pytest as the testing framework
• Mocks all external dependencies (Docker, subprocess calls, GitHub CLI)
• Doesn't require s390x architecture to run tests
• Runs in CI/CD pipeline automatically

cc @rposts @pleia2

[rohansen856]

@rposts If the approach looks okay i will do further investigation and write tests (and gh action) for this. Thanks.