fix(ccip/integration-tests): mine each tx in commitSqNrs to avoid nonce race

[Fletch153]

Smoking gun

ccip_reader_test.go:515:
    Error Trace: .../integration-tests/smoke/ccip/ccip_reader_test.go:515
    Error:       Received unexpected error:
                 replacement transaction underpriced
    Test:        TestCCIPReader_ExecutedMessages_MultiChainDisjoint

CI: #22016 run 24424913522 job 71356857697. Reproduces on base branch (not introduced by #22016).

Root cause

commitSqNrs (ccip_reader_test.go:1204) loops EmitExecutionStateChanged with no Commit() between iterations:

for _, sqnr := range seqNums {
    _, err := s.contract.EmitExecutionStateChanged(s.auth, ...)
    ...
}

Generated binding in chainlink-ccip/.../ccip_reader_tester/ccip_reader_tester.go:357 is a straight-through contract.Transact(opts, "emitExecutionStateChanged", ...) — it sends a tx to the simulated mempool and does not mine. Only s.sb.Commit() mines.

s.auth is constructed by setupSimulatedBackendAndAuth with Nonce==nil, so BoundContract.transact calls PendingNonceAt(opts.From) for each tx. On ethclient/simulated the pending-pool nonce update is asynchronous with SendTransaction returning, so two back-to-back sends can read the same pending nonce. The second tx then lands at an already-occupied mempool nonce with the same suggested gas price → go-ethereum returns ErrReplaceUnderpriced ("replacement transaction underpriced").

Why only _MultiChainDisjoint

Only that test passes multi-element seqNums:

Caller (line)	seqNums	Loops?
429, 433, 437, 441, 471, 475	1 element	no
514	[15, 17, 70]	yes
518	[15, 16]	yes

Single-element callers never hit the race.

Fix

Mirror emitCommitReports (line 1635), which already commits inside its loop. Add s.sb.Commit() at the end of each iteration of commitSqNrs so the next iteration's PendingNonceAt sees the bumped state nonce. Single-element callers are unaffected — the extra commit is an empty block after the existing outer Commit(); lp.Replay(ctx, 1) reads from block 1 regardless.

Verification

go test -count=10 -run TestCCIPReader_ExecutedMessages_MultiChainDisjoint ./integration-tests/smoke/ccip/ — 10/10 green.
Full TestCCIPReader_ExecutedMessages* — green.

Scope

Single file, +1 line. No production code touched.

[github-actions]

✅ No conflicts with other open PRs targeting develop

[trunk-io]

     

Failed Test	Failure Summary	Logs
Test_CCIPProgrammableTokenTransfer_EVM2Sui_BurnMintTokenPool	The test failed due to an unspecified error during execution, with no clear indication of the specific issue from the provided logs.	Logs ↗︎

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[cl-sonarqube-production]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarQube

[Fletch153]

Superseded by #22031 (fresh branch off latest develop, identical diff).