Added tests for BackoffPolicy

[KengoWada]

Proposed changes

Added tests for BackoffPolicy

Related issue(s)

Fixes #6

Checklist

Please ensure that the following checks have been performed:

• I have read and followed the project's contributing guidelines.
• My code follows the project's coding style.
• I have added or updated relevant documentation.
• I have added or updated tests (if applicable).
• All new and existing tests pass.
• My changes do not introduce any new warnings or errors.

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 41.95%. Comparing base (c76e555) to head (bc1d787).

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop       #7      +/-   ##
===========================================
+ Coverage    39.16%   41.95%   +2.79%     
===========================================
  Files            4        4              
  Lines          143      143              
===========================================
+ Hits            56       60       +4     
+ Misses          86       83       -3     
+ Partials         1        0       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.