test(plugins): add result normalization contract tests for all bundled parsers (#231)

[vikas-6]

📝 Description

This PR implements a centralized integration contract test suite validating that every single one of the 60 custom bundled parsers complies strictly with the required parser interface and normalization constraints (resolves #231).

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🚀 Key Features & Changes

1. Centralized Contract Verification Suite (testing/backend/integration/test_parser_output_contract.py)

• Dynamic Parser Discovery & Loading: Scans the plugins/ directory, dynamically imports parser.py modules, and verifies the required parse(output: str) entrypoint exists and is callable.
• Empty Shape Resilience: Asserts that empty strings or empty structures passed to the normalization logic are handled gracefully without raising unhandled server crashes.

2. Strict Input & Structure Guardrails (Negative Tests)

• Malformed Shape Fallbacks: Ensures that incomplete or malformed finding records default safely (falling back to the capitalized plugin category, default titles, empty string remediations, and empty metadata dictionaries).
• Valid Severity Mappings: Asserts that standard parser severities (critical, high, medium, moderate, warning, low, info, informational, error) are accurately translated.
• Unsafe/Unknown Severity Sanitization: Verifies that unknown or malicious severities (e.g. critical-critical, severe, malicious, None, integers, or blank strings) are safely defaulted to info to protect database inserts.
• Shape Type Filtering: Verifies that any malformed elements in the findings list that are not represented as dictionaries (e.g. strings, integers, or lists) are strictly filtered out and rejected.

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🧪 Verification & Formatting Hygiene

• Formatting Hygiene: The new test file has been cleaned of all trailing whitespaces. Verified locally with git diff --check, resulting in a perfectly clean pass.
• Test Session Success: All 60 custom parsers dynamically loaded and passed the strict contract validations successfully:

  $ pytest testing/backend -k test_parser_contract_compliance
  testing/backend/integration/test_parser_output_contract.py ............................................................ [100%]
  ================ 60 passed in 0.15s =================

• Test Baseline: Confirmed that all 336 existing unit and integration tests continue to pass with absolute success.

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📋 Checklist

• Dynamic discovery of all 60 bundled custom parsers implemented.
• Required parse callable entrypoint verified across all parsers.
• Normalization layer resilience to empty/null shapes validated.
• Severity mappings and malformed fallbacks verified.
• Explicit negative tests for unknown severities and malformed shapes implemented.
• Staged, committed, and pushed clean code without unrelated lockfile/doc churn.

[vikas-6]

Hi @utksh1!

I have resolved this issue by implementing a centralized integration contract test suite that dynamically loads and verifies all 60 bundled custom parsers against the backend normalization constraints.

Here is the PR: #292 (or your PR number once created!)

Please review and merge it. Thank you!