fix: improve test_nvd_api

[Saksham-Sirohi]

Overview

This PR introduces comprehensive unit tests for critical functions in nvd_api.py, ensuring better test coverage without adding stress to the NVD API. All tests are mocked and avoid real API calls, adhering to the project's guidelines on minimizing external resource usage.

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Changes

1. New Unit Tests:

   • Added tests for convert_date_to_nvd_date_api2, get_reject_count_api2, nvd_count_metadata, validate_nvd_api, and load_nvd_request.
   • Mocked API responses using AsyncMock and FakeResponse to simulate various scenarios (e.g., invalid API keys, rejected CVEs).

2. Preserved Existing Tests:

   • All original integration tests (e.g., test_nvd_incremental_update) remain unchanged and are conditionally skipped unless EXTERNAL_SYSTEM=1 is set.

3. No Breaking Changes:

   • The new tests are additive and do not modify or override existing functionality.

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Why This Matters

• Improved Coverage: Core functions like date formatting, API key validation, and CVE rejection handling are now thoroughly tested.
• Zero Real API Calls: All tests use mocked data, avoiding unnecessary load on the NVD API.
• Safer Refactoring: Future changes to these functions can be validated without relying on external services.

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Testing

• New Tests:

  • test_convert_date_to_nvd_date_api2: Validates date formatting for NVD API compliance.
  • test_get_reject_count_api2: Ensures rejected CVEs are correctly counted.
  • test_nvd_count_metadata: Verifies metadata parsing from mocked API responses.
  • test_validate_nvd_api: Tests API key removal on invalid responses.
  • test_load_nvd_request: Checks pagination logic and total result calculation.

• Existing Tests:

  • All original integration tests pass as expected.

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Steps to test

EXTERNAL_SYSTEM=1 pytest -v test/test_nvd_api.py

Related Issues Fixes #4877

[Saksham-Sirohi]

hi @terriko can you please take a look at the changes i have made and whether this aligns with what we had in mind towards coverage of nvd API