docs(parser): annotate every test with its CASE.* in TEST_CASES.md

[keivenchang]

hey guys, I'm just doing a trivial (NO CODE CHANGE) doc reorg so the docs read more clearly and the tests are categorized so we have an idea of coverage. all 389 tests still pass.

paired with DIS-1842's contract test scaffold (#8728) — that PR adds runnable cross-parser tests, this one makes existing per-parser tests greppable.

[coderabbitai]

Walkthrough

A documentation file was extended with new test case categories (CASE.20–CASE.24) defining parser-internal detection scenarios and edge cases. Across multiple parser modules, unit test functions received inline case-identifying comments (e.g., // CASE.X) appended to their #[test] attributes for tracking test coverage taxonomy alignment. No production logic or test behavior was modified.

Changes

Cohort / File(s)	Summary
Test Case Documentation lib/parsers/TESTING.md	Extended taxonomy with new categories CASE.20–CASE.24 clarifying test coverage expectations for parser-internal helpers, identifier/regex handling, whitespace robustness, section-token variants, and empty tool-call sections.
Reasoning Parsers Test Annotations lib/parsers/src/reasoning/base_parser.rs, gpt_oss_parser.rs, granite_parser.rs, minimax_append_think_parser.rs, mod.rs	Updated multiple #[test] and #[rstest] attributes with inline // CASE.* comment labels. No test logic or assertions altered.
Tool Calling — JSON Parsers Test Annotations lib/parsers/src/tool_calling/json/base_json_parser.rs, deepseek_v3_parser.rs, deepseek_v3_1_parser.rs, mod.rs	Appended case-identifying comments to #[test] attributes across multiple detect and parse test functions. No behavioral changes.
Tool Calling — XML Parsers Test Annotations lib/parsers/src/tool_calling/xml/glm47_parser.rs, kimi_k2_parser.rs, parser.rs	Added inline // CASE.* labels to #[test] and #[rstest] functions. No parsing logic or control flow affected.
Tool Calling — Other Parsers Test Annotations lib/parsers/src/tool_calling/dsml/parser.rs, harmony/harmony_parser.rs, pythonic/pythonic_parser.rs	Updated test attributes with case taxonomy comments. No test implementations or assertions modified.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (1 warning, 1 inconclusive)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 6.15% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.
Description check	❓ Inconclusive	PR description is minimal but conveys intent: documentation-only reorganization annotating 232 tests with case labels and adding 5 new TESTING.md entries. Core purpose (test taxonomy cross-indexing) and scope (no code changes, 389 tests pass) are clear.	Add structured sections matching template: Overview, Details (specific file changes), Where to start (recommended review entry point), and Related Issues reference. Currently lacks organization against template structure.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Related issues and internal tracking (DIS-1842, PR #8724) are mentioned in the description; the PR is correctly positioned as a companion to the contract test scaffold work and applies independently to all parser tests.
Out of Scope Changes check	✅ Passed	All changes are scoped to test annotations and TEST_CASES.md documentation within lib/parsers/; no production code, test logic, or assertions were modified; integration tests under lib/llm/tests/ are correctly deferred.
Title check	✅ Passed	The PR title accurately summarizes the main change: adding CASE.* annotations to every test in the parser suite and updating TESTING.md. It is concise, specific, and directly reflects the changeset.

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[keivenchang]

Superseded by #8729 — head branch renamed to add the DIS-1842 prefix per branch-naming convention; GitHub auto-closed this PR despite the rename API saying it should migrate. All work continues there.

[ayushag-nv]

@keivenchang Just one comment, do we need the TEST_CASES.md file in the repo. I won't prefer that. May be you can add it as a skill in .claude or something if you want to use it as testing skill ?

[MatejKosec]

Thanks for doing this!

[keivenchang]

@keivenchang Just one comment, do we need the TEST_CASES.md file in the repo. I won't prefer that. May be you can add it as a skill in .claude or something if you want to use it as testing skill ?

Will address this in the next PR, we'll have skill (how to do something) and the md file (what corner cases we have) reference each other. Coming up!