test(cli): route MaxInstances duplicate checks to a stub transport

[cristim]

Closes #2148

Summary

The MaxInstances tests in cmd/multi_service_max_instances_test.go mocked only the recommendation fetch. The duplicate check (checkDuplicates → createServiceClient → GetExistingCommitments) still sent real DescribeReservedDBInstances / DescribeReservedCacheNodes requests to AWS.

This change is test-only. No production code changes.

• maxInstancesAWSStub is injected through aws.Config.HTTPClient. It serves empty Query-protocol fixtures keyed by host and Action, and fails the test on any other request.
• newMaxInstancesAWSConfig sets static fake credentials and no retries, so signing needs no environment and nothing reaches IMDS or STS.
• requireDuplicateChecks asserts exactly one duplicate-check request per (service, region) pair: 2 services × 3 regions.
• A fixture the SDK cannot parse is only logged as a warning on a dry run. To catch that, the tests capture AppLogger through the existing captureAppLog helper and assert that "Could not check for existing RIs" never appears.
• The existing ordering and capping assertions are unchanged.

Out of scope: TestRunToolFromCSV_WithMaxInstances and TestFilterAndAdjustRecommendations_MaxInstancesApplied still reach AWS. #2162 tracks those.

Evidence

Local runs on macOS with GOTOOLCHAIN=go1.26.9; fixture-based.

• Before the change: with HTTPS_PROXY pointed at a CONNECT-logging listener, TestMaxInstancesKeepsHighestSavingsNotFirstFetched made 12 CONNECTs to rds and elasticache in us-east-1, us-west-2 and eu-west-1. The test passed anyway, after about 10s.
• After the change: the TestMaxInstances* tests pass with HTTPS_PROXY=127.0.0.1:1. An independent reviewer confirmed that -run TestMaxInstances makes zero CONNECTs.
• Mutation probes:
  • Deleting the rds eu-west-1 fixture fails with "unexpected AWS request POST rds.eu-west-1.amazonaws.com DescribeReservedDBInstances".
  • Malformed RDS or ElastiCache fixture XML fails all four fetch tests. Before the log assertion was added, those tests passed.
• Checks:
  • make build, go vet ./... and go test -race ./cmd/... pass.
  • -race -count=2 -shuffle=on -run TestMaxInstances passes.
  • golangci-lint v2.10.1 (the CI pin) reports 0 issues.
  • scripts/test-git-secrets-allowlist.sh: 44/44.
• Review: an independent non-author reviewer (sonnet, high) did two passes.
  • Pass 1 found one medium issue: a broken fixture could pass silently. It is fixed.
  • Pass 1 also flagged that the CSV-path leak is out of scope; test(cmd): existing tests reach real AWS endpoints #2162 tracks it.
  • Pass 2 found no actionable findings at 39198c1.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Tests
  • Expanded coverage of multi-service, multi-region instance limits, savings-based selection, minimum counts, and unset limits.
  • Verified AWS request handling for each service-region combination using offline test responses.

[coderabbitai]

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 39198c1 and 65d9fee.

📒 Files selected for processing: 1

• cmd/multi_service_max_instances_test.go

🚧 Files skipped from review as they are similar to previous changes: 1

• cmd/multi_service_max_instances_test.go

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📝 Walkthrough

The MaxInstances tests use a stubbed AWS transport for duplicate checks. They verify that each service-region pair generates one request and that no duplicate-check parse warning occurs.

Changes: Duplicate-check test isolation

Layer / File(s)	Summary
Stub and verify duplicate-check requests cmd/multi_service_max_instances_test.go	A test transport serves recognized RDS and ElastiCache fixtures, records requests, and rejects unrecognized requests. Four MaxInstances tests use the stubbed AWS config and assert one duplicate-check request per service-region pair.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Other · Severity of issue fixed: Low

Merge Risk: ⚪ Minimal · up to 65d9f

The MaxInstances tests appear ready to merge after normal checks; no actionable risk remains in the supplied evidence.

Pre-merge checks: 5

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: routing MaxInstances duplicate-check requests through a stub transport in CLI tests.
Linked Issues check		The changes satisfy the coding requirements in [#2148]. cmd/multi_service_max_instances_test.go injects an aws.Config.HTTPClient transport, serves controlled RDS and ElastiCache Query fixtures, an…
Out of Scope Changes check		The reviewed change is limited to cmd/multi_service_max_instances_test.go. The stub, fixtures, request-count checks, log checks, and retained assertions directly support [#2148]. No unrelated produc…
Docstring Coverage		Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 1 files.

Full details: Linked Issues check

Explanation

The changes satisfy the coding requirements in [#2148]. cmd/multi_service_max_instances_test.go injects an aws.Config.HTTPClient transport, serves controlled RDS and ElastiCache Query fixtures, and reports unexpected requests as test failures. Anonymous credentials and aws.NopRetryer remove credential and retry dependencies. The tests assert one parsed duplicate-check request for each of 2 services and 3 regions, while retaining ordering, capping, and minimum-count assertions. The supplied verification reports closed-proxy isolation and race-test success. The reviewed change is test-only, so production behavior remains unchanged.

Full details: Out of Scope Changes check

Explanation

The reviewed change is limited to cmd/multi_service_max_instances_test.go. The stub, fixtures, request-count checks, log checks, and retained assertions directly support [#2148]. No unrelated production or feature changes are shown. The CSV-path and filter-and-adjust tests are explicitly excluded and tracked separately; their existing AWS access is not a change introduced by this pull request.

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[coderabbitai]

Actionable comments posted: 2

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• 🪄 Fix comments: Fix CodeRabbit comments on this PR

🤖 Prompt to fix review comments

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Inline comments:
Review comments at @cmd/multi_service_max_instances_test.go:
- Around line 97-104: Update the request-count assertions in the test’s
`s.received` loop to require exactly one request for each key in
`maxInstancesAWSFixtures`, while retaining the check that rejects unexpected
keys. Keep the existing total-count and warning assertions.
- Around line 82-84: Replace the hardcoded credentials provider in the test’s
AWS configuration with aws.AnonymousCredentials{} so stubbed requests are
unsigned and no credentials are embedded in the source.

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• cmd/multi_service_max_instances_test.go

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[cristim]

Automated review of 39198c1: no blocking findings and CI is green. Ready to merge.
Test-only change. The stub transport, fixtures and request-count and log assertions are sound. captureAppLog exists and the asserted warning string matches production code. CI is green. No blocking issues.

• (optional) cmd/multi_service_max_instances_test.go:57: RoundTrip ignores errors from io.ReadAll and url.ParseQuery. A parse failure would yield an empty Action and an 'unexpected request' error, so it still fails loudly, but the real cause would be hidden.

Posted by a read-only review sweep. It stays silent on this commit and re-reviews only after a new push.

[cristim]

Independent review verdict: CLEAN at 65d9fee

Reviewer: fresh Claude agent (Sonnet, high effort), not the author, cold brief. Pass 1 covered the full diff at 39198c1; pass 2 covered the delta to 65d9fee. Coordinator: claude-cc-reviewer.

Blocking findings: none.

Pass 1 (39198c1), what was attacked:

• Every AWS client in the MaxInstances duplicate-check tests comes from the stub aws.Config (including NewAccountAliasCache), and an unfixtured request calls t.Errorf. There is no LoadDefaultConfig, and no global transport or env change.
• The old assertions are untouched, and the change only adds checks.
• go test -race -count=1 ./cmd/... passes, and -count=20 -run MaxInstances gave 120 passed.
• Fail-before: origin/main's tests under HTTPS_PROXY=http://127.0.0.1:9 really hit the network ("Could not check for existing RIs ... connection refused") and still passed. The new tests pass in ~0s.
• Mutation probes: a malformed fixture, a missing fixture and a count+1 were each killed.
• Non-blocking nit: the stub ignores ReadAll/ParseQuery errors, but a bad body still fails loudly as an unexpected request.

Pass 2 (delta 39198c1..65d9fee), the CodeRabbit actionables:

• aws.AnonymousCredentials{} is used, and a probe confirmed no Authorization header is sent.
• requireDuplicateChecks asserts exactly one request per key. A double-count mutation is killed.
• -count=3 -run MaxInstances passes, and go vet is clean.

Gate:

• CI is green at 65d9fee, and mergeability is CLEAN.
• Labels are mirrored from test(cli): isolate ancillary AWS calls in MaxInstances mock tests #2148.
• CodeRabbit re-reviewed 65d9fee with 0 actionables, and both earlier threads were answered with the fix commit. (claude-cc-reviewer)