Fix issue 369 in AiDotNet

[ooples]

Implements 128 test methods across 4 compressor classes to achieve 80%+ code coverage for the RAG context compression module.

Test Coverage:

• LLMContextCompressor: 35 tests covering constructor validation, basic functionality, compression quality, edge cases, and integration scenarios
• DocumentSummarizer: 33 tests for summarization logic, query-aware compression, and boundary conditions
• SelectiveContextCompressor: 32 tests for sentence selection, relevance filtering, and threshold behavior
• AutoCompressor: 28 tests for rule-based compression, scoring algorithms, and performance

Base Test Infrastructure:

• ContextCompressorTestBase: Shared utilities including sample document creation, compression verification, metadata/score preservation checks, and helper methods for Unicode, special characters, and large documents

Test Categories:

• Constructor validation (parameter bounds, null checks)
• Basic functionality (valid inputs, null/empty handling)
• Compression quality (output length, relevance preservation, metadata/score handling)
• Edge cases (empty documents, single sentences, 100KB+ documents, Unicode, special characters)
• Integration scenarios (multiple compressors, different parameters, consistency)

Resolves #369

User Story / Context

• Reference: [US-XXX] (if applicable)
• Base branch: merge-dev2-to-master

Summary

• What changed and why (scoped strictly to the user story / PR intent)

Verification

• [ ] Builds succeed (scoped to changed projects)
• [ ] Unit tests pass locally
• [ ] Code coverage >= 90% for touched code
• [ ] Codecov upload succeeded (if token configured)
• [ ] TFM verification (net46, net6.0, net8.0) passes (if packaging)
• [ ] No unresolved Copilot comments on HEAD

Copilot Review Loop (Outcome-Based)

Record counts before/after your last push:

• Comments on HEAD BEFORE: [N]
• Comments on HEAD AFTER (60s): [M]
• Final HEAD SHA: [sha]

Files Modified

• [ ] List files changed (must align with scope)

Notes

• Any follow-ups, caveats, or migration details

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📥 Commits

Reviewing files that changed from the base of the PR and between cfbfef224322c26ddd4759ddc8861c97dead3962 and b006aab34f24ccd0d7099692e47e0e075d7c3ef6.

📒 Files selected for processing (1)

• commitlint.config.js (1 hunks)

Summary by CodeRabbit

Release Notes

• Bug Fixes

  • Improved ellipsis handling in document summarization to ensure consistent formatting when truncating long content to fit length constraints.

• Tests

  • Added comprehensive test coverage for context compression features, including multiple compression strategies, edge cases, Unicode handling, and metadata preservation.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

Walkthrough

Adds extensive unit tests and shared test utilities for RAG context compression and updates DocumentSummarizer truncation to reserve space for an ellipsis when truncating summaries (ellipsis-aware truncation behavior).

Changes

Cohort / File(s)	Summary
Test Base Utilities tests/AiDotNet.Tests/UnitTests/RetrievalAugmentedGeneration/ContextCompression/ContextCompressorTestBase.cs	New abstract test base providing shared helpers: numeric ops, sample document creators (CreateSampleDocuments, CreateDocumentWithLength, CreateLargeDocument, CreateUnicodeDocument, CreateSpecialCharDocument), and assertion/metric helpers (AssertCompressed, CalculateCompressionRatio, AssertMetadataPreserved, AssertRelevanceScoresPreserved).
AutoCompressor Tests tests/AiDotNet.Tests/UnitTests/RetrievalAugmentedGeneration/ContextCompression/AutoCompressorTests.cs	New comprehensive unit tests for AutoCompressor<T> covering constructor validation, compression behavior (null/empty inputs, edge cases), size/relevance preservation, metadata and ID retention, numeric-type variability, and performance/repeatability scenarios.
DocumentSummarizer Implementation src/RetrievalAugmentedGeneration/ContextCompression/DocumentSummarizer.cs	Adjusted truncation logic to be ellipsis-aware: reserves space for an ellipsis when truncating to _maxSummaryLength, truncates the first/important sentence with ellipsis when needed, and handles very-small max lengths without breaking lengths. No public signature changes.
DocumentSummarizer Tests tests/AiDotNet.Tests/UnitTests/RetrievalAugmentedGeneration/ContextCompression/DocumentSummarizerTests.cs	New test suite for DocumentSummarizer<double> exercising constructor validation, summarization behavior (length limits, query prioritization), edge cases (Unicode, special chars, large docs), SummarizeText/Summarize methods, metadata/relevance/ID preservation, and deterministic behavior.
LLMContextCompressor Tests tests/AiDotNet.Tests/UnitTests/RetrievalAugmentedGeneration/ContextCompression/LLMContextCompressorTests.cs	New tests for LLMContextCompressor<T> validating constructor params, Compress/CompressText behavior, compression ratios, metadata/relevance preservation, edge cases (small/large/Unicode), multi-document handling, and repeatability.
SelectiveContextCompressor Tests tests/AiDotNet.Tests/UnitTests/RetrievalAugmentedGeneration/ContextCompression/SelectiveContextCompressorTests.cs	New tests for SelectiveContextCompressor covering constructor parameter validation (maxSentences, relevanceThreshold), sentence selection/ordering, relevance filtering, metadata/relevance/ID preservation, edge cases, numeric-type support, and deterministic results across invocations.

Sequence Diagram(s)

(omitted — changes are test additions and a localized truncation behavior update; no new multi-component sequential flow to diagram)

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~45 minutes

• Pay special attention to:
  • src/RetrievalAugmentedGeneration/ContextCompression/DocumentSummarizer.cs — verify ellipsis-aware truncation edge cases and length calculations.
  • tests/.../ContextCompressorTestBase.cs — ensure helper methods correctly model document shapes and numeric ops.
  • tests/.../AutoCompressorTests.cs and others — confirm consistency of assertions across test suites, coverage for numeric-type variations, and deterministic expectations.

Poem

🐇 In fur and tests I hop and write,

Sentences trimmed with ellipsis light,
Compressors checked from end to start,
Metadata safe, relevance a part,
Repeats the same — a rabbit's delight! 🎀

Pre-merge checks and finishing touches

❌ Failed checks (2 warnings, 1 inconclusive)

Check name	Status	Explanation	Resolution
Out of Scope Changes check	⚠️ Warning	One minor out-of-scope change detected: src/RetrievalAugmentedGeneration/ContextCompression/DocumentSummarizer.cs includes logic changes (ellipsis-aware truncation) beyond the test coverage objective.	Separate the DocumentSummarizer.cs implementation change into a distinct PR, or clarify if the ellipsis feature is part of issue #369's scope.
Docstring Coverage	⚠️ Warning	Docstring coverage is 7.19% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.
Title check	❓ Inconclusive	Title 'Fix issue 369 in AiDotNet' is vague and generic, referring to 'issue 369' without explaining the actual change (implementing comprehensive tests for RAG context compression).	Use a more descriptive title that conveys the main purpose, such as 'Add comprehensive test coverage for RAG context compression module' or 'Implement 128 tests for context compression classes'.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description clearly outlines 128 test methods across 4 compressor classes, test infrastructure, coverage targets, and references issue #369, providing relevant context about the changeset.
Linked Issues check	✅ Passed	All objectives from issue #369 are met: comprehensive test suites (128 tests across 4 classes) covering constructors, functionality, edge cases, and quality metrics target 80%+ coverage for the RAG context compression module.

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