test: log-buffer, RWLock concurrency, SSE chunk splitting — 13 new tests

[anandgupta42]

What does this PR do?

Adds 13 new tests across 3 modules that had zero or minimal test coverage, targeting real user-facing risk areas identified during automated test discovery.

1. bufferLog / getRecentDbtLogs / clearDbtLogs — packages/dbt-tools/src/log-buffer.ts (6 new tests)

This ring buffer captures dbt log output to prevent TUI corruption (referenced in #249). Zero tests existed. New coverage includes:

• Insertion order preservation
• Oldest-entry eviction when the 100-message cap is exceeded
• Buffer clearing resets state completely
• getRecentDbtLogs() returns a defensive copy (not a mutable reference to internal state)
• Correct behavior at boundary (200 messages → exactly 100 retained, correct window)
• Empty buffer returns empty array

2. Lock.read / Lock.write — packages/opencode/src/util/lock.ts (2 new tests, 3 total)

The RWLock powers session concurrency. Only 1 test existed (basic writer exclusivity). New coverage includes:

• Concurrent readers: multiple readers acquire simultaneously without blocking
• Writer starvation prevention: a queued writer blocks subsequent readers, ensuring writers are not starved by a steady stream of read requests (tests the process() priority logic)

3. parseSSE — packages/opencode/src/control-plane/sse.ts (5 new tests, 7 total)

The SSE parser powers real-time workspace sync via the control plane. Only 2 basic tests existed. New coverage includes:

• Event data split across chunk boundaries (buffer accumulation correctness)
• \n\n delimiter split across two chunks (the most dangerous boundary case)
• Empty events (consecutive \n\n with no data lines) are correctly ignored
• Abort signal stops processing mid-stream (uses pull()-based stream for reliable abort timing)
• Bare \r line endings are normalized correctly (existing tests only covered \r\n)

Type of change

• New feature (non-breaking change which adds functionality)

Issue for this PR

N/A — proactive test coverage via automated test discovery

How did you verify your code works?

bun test packages/dbt-tools/test/log-buffer.test.ts          # 6 pass
bun test packages/opencode/test/util/lock.test.ts            # 3 pass (1 existing + 2 new)
bun test packages/opencode/test/control-plane/sse.test.ts    # 7 pass (2 existing + 5 new)

All tests validated by a critic agent before commit (rejected 2 proposed tests as redundant/flawed, revised 2 others for correctness).

Checklist

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

https://claude.ai/code/session_01153R7Dh9BMKiarndEUraBk

Summary by CodeRabbit

• Tests
  • Enhanced test coverage for log buffer operations, including overflow handling and buffer isolation.
  • Extended test coverage for SSE parsing to handle chunked payloads, split delimiters, and stream interruption scenarios.
  • Added test coverage for concurrent read locking and writer-priority behavior in lock mechanisms to prevent starvation.

[claude]

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[coderabbitai]

📝 Walkthrough

Walkthrough

This pull request adds comprehensive test suites across three modules: a new test suite for the DBT log buffer module testing core buffer behaviors and overflow handling; five new test cases for SSE parsing covering edge cases including split tokens, event delimiters across chunks, abort signals, and carriage-return line endings; and two new test cases for Lock concurrency testing concurrent reads and writer-priority behavior.

Changes

Cohort / File(s)	Summary
DBT Log Buffer Tests packages/dbt-tools/test/log-buffer.test.ts	New test suite verifying buffer operations: message ordering, 100-entry overflow capacity with oldest entry eviction, clearing functionality, immutable copy return values, and empty buffer handling.
SSE Parser Edge Cases packages/opencode/test/control-plane/sse.test.ts	Five new test cases covering: split tokens across chunk boundaries, event delimiters split across chunks, empty event ignoring, abort signal handling mid-stream, and carriage-return line ending parsing.
Lock Concurrency packages/opencode/test/util/lock.test.ts	Two new test cases verifying concurrent read lock acquisition without blocking and writer-priority behavior with reader starvation prevention.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Possibly related PRs

• #411: Adds SSE test adjustments for parseSSE behavior alongside similar test coverage for edge cases

Suggested labels

contributor

Poem

🐰 Test cases hop and play,
Buffering logs the rabbit way,
Locks and streams align just right,
Coverage shines both day and night!
Thump thump—all green, hooray! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically summarizes the main change: adding 13 new tests across three modules with a concise, concrete focus on the tested areas.
Description check	✅ Passed	The pull request description comprehensively covers all template sections: it details what changed and why (specific modules and test rationale), provides test verification output (how it was tested), and includes checklist confirmations.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch test/hourly-20260327-2019

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[coderabbitai]

🧹 Nitpick comments (1)

packages/dbt-tools/test/log-buffer.test.ts (1)

43-50: Consider caching getRecentDbtLogs() result to avoid repeated calls.

The function is called three times for assertions. While not a bug, storing the result in a variable improves readability and consistency with the earlier test at lines 20-23.

♻️ Suggested refactor

   test("buffer stays at exactly 100 after repeated overflow", () => {
     for (let i = 0; i < 200; i++) {
       bufferLog(`msg-${i}`)
     }
-    expect(getRecentDbtLogs()).toHaveLength(100)
-    expect(getRecentDbtLogs()[0]).toBe("msg-100")
-    expect(getRecentDbtLogs()[99]).toBe("msg-199")
+    const logs = getRecentDbtLogs()
+    expect(logs).toHaveLength(100)
+    expect(logs[0]).toBe("msg-100")
+    expect(logs[99]).toBe("msg-199")
   })

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@packages/dbt-tools/test/log-buffer.test.ts` around lines 43 - 50, The test
repeatedly calls getRecentDbtLogs() three times; cache its result in a local
variable (e.g., const logs = getRecentDbtLogs()) after filling the buffer with
bufferLog(...) and use that variable for the three assertions (length and index
checks) to improve readability and avoid redundant calls to getRecentDbtLogs().

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@packages/dbt-tools/test/log-buffer.test.ts`:
- Around line 43-50: The test repeatedly calls getRecentDbtLogs() three times;
cache its result in a local variable (e.g., const logs = getRecentDbtLogs())
after filling the buffer with bufferLog(...) and use that variable for the three
assertions (length and index checks) to improve readability and avoid redundant
calls to getRecentDbtLogs().

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: fe4b9d11-57a1-4c0a-b0c3-8c6c52669d00

📥 Commits

Reviewing files that changed from the base of the PR and between 86a02c4 and fa6288b.

📒 Files selected for processing (3)

• packages/dbt-tools/test/log-buffer.test.ts
• packages/opencode/test/control-plane/sse.test.ts
• packages/opencode/test/util/lock.test.ts

[anandgupta42]

Consolidated into #545