test: cover the Scylla connection-setup helpers (DRIVER-1000)

[nikagra]

Two Scylla-only helpers run while a connection is being brought up, and the 4.x coverage report shows both barely exercised: LwtInfo has no test at all (72% of lines), and RejectionSafeEventExecutor has exactly one, covering only the rejection path (50%).

LwtInfo is the riskier of the two. It parses the LWT bit mask out of the server's SUPPORTED options and echoes it back in STARTUP; get that wrong and the driver silently misclassifies LWT statements, which changes routing.

• LwtInfoTest: every path that returns null (option absent, null list, list without exactly one entry, null value, wrong prefix, unparsable number), and the STARTUP round trip.
• The case worth having: the server sends the mask as an unsigned int32. 2147483648, the value Scylla actually sends, must fold to Integer.MIN_VALUE, and isLwt is exercised with that sign-bit mask, where a signed comparison would break. What goes back in STARTUP is then the signed form — 4294967295 is echoed as -1 — which nothing asserted before.
• RejectionSafeEventExecutorTest: the non-rejecting path, both inEventLoop overloads, and the lifecycle/shutdown delegation surface.

Both classes reach 100% line and branch coverage: 16 missed lines and 5 missed branches closed against baseline run 34559159215.

Verified with mvn clean test -pl core (3985 unit tests green, up from 3968), and by mutation: isLwt rewritten as (flags & mask) > 0, and the STARTUP value written with Integer.toUnsignedString, each passes the old tests and fails the new ones. No integration lane was run; these are pure unit tests with no server dependency.

One of several independent PRs for DRIVER-1000, all off scylla-4.x, not a stack. Siblings: #1082, #1084, #1086.

Refs: https://scylladb.atlassian.net/browse/DRIVER-1000

[coderabbitai]

Important

Draft PR not reviewed

Draft PRs are not automatically reviewed by default.

• Trigger a manual review

To automatically review draft PRs, update your CodeRabbit configuration:

reviews:
  auto_review:
    drafts: true

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}