test(staleness): pin exact-timeout and just-stale LTS boundary tests

[thedavidmeister]

Closes #55

Problem

testFtsoV2LTSGetFeedStale exercised only a single stale point (warp +3601 over a 3600 timeout). The off-by-one boundary of the block.timestamp > timestamp + timeout predicate was unverified: a regression flipping > to >= (or an off-by-one in the timeout arithmetic) would not be caught.

timeout == 0 (every block is stale once the feed is updated) was also unexercised.

Fix

Adds four boundary tests to LibFtsoV2LTSTest:

Test	condition	expected
testFtsoV2LTSGetFeedExactTimeoutNotStale	block.timestamp == feedTimestamp + timeout	succeeds (strict > so equal is not stale)
testFtsoV2LTSGetFeedJustStale	block.timestamp == feedTimestamp + timeout + 1	reverts StalePrice
testFtsoV2LTSGetFeedTimeoutZeroStale	timeout == 0, block.timestamp = feedTimestamp + 1	reverts StalePrice
testFtsoV2LTSGetFeedTimeoutZeroExactNotStale	timeout == 0, block.timestamp == feedTimestamp	succeeds

All four tests use vm.warp(absolute) anchored to the hardcoded feed timestamp 1729795768 (the ETH_USD feed value at BLOCK_NUMBER = 31843105, already used in the existing stale test). All 7 LibFtsoV2LTSTest tests pass.

Summary by CodeRabbit

• Tests
  • Added coverage for feed freshness edge cases, including exact timeout boundaries and zero-timeout behavior.
  • Improved validation that stale feed values correctly revert while fresh values remain usable.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: ad25e9db-29d3-45f3-bc33-6e75e0d1b164

📥 Commits

Reviewing files that changed from the base of the PR and between cb20d03 and 622443d.

📒 Files selected for processing (1)

• test/src/lib/lts/LibFtsoV2LTS.t.sol

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Walkthrough

Four new test functions are added to LibFtsoV2LTSTest covering boundary behavior of the FTSO V2 LTS staleness predicate (block.timestamp > feedTimestamp + timeout): exact boundary (not stale), one second past boundary (stale), timeout==0 with later timestamp (stale), and timeout==0 at exact feed timestamp (not stale).

Changes

FTSO V2 LTS staleness boundary tests

Layer / File(s)	Summary
Staleness boundary and timeout==0 tests test/src/lib/lts/LibFtsoV2LTS.t.sol	Adds four tests using vm.warp and vm.expectRevert to verify both sides of the block.timestamp > feedTimestamp + timeout boundary and both sides of the timeout==0 edge case.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title is concise and accurately highlights the staleness boundary test additions.
Linked Issues check	✅ Passed	The PR covers the requested exact-timeout, one-second-over, fresh feed, and zero-timeout boundary cases pinned to the target fork.
Out of Scope Changes check	✅ Passed	The changes stay focused on the linked staleness-boundary tests in the specified LTS test file.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch 2026-06-30-issue-55-staleness-boundary

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