test(vertexai): keep RPC replay independent of external network - #1548

Linked issue

Related to #1507. Validation of its runner fix, #1547, exposed this separate VertexAI replay-harness problem

Description of change

Problem: setupReplay used Replayer.DialOptions(), including grpc.WithBlock(). Constructing the session client attempted to connect to the real Vertex AI endpoint before recorded RPCs could replay. The original regression only detected blocking construction: removing WithBlock let an external dial attempt pass the test

Solution: Replay mode supplies Replayer.Connection() through option.WithGRPCConn. Recording mode keeps its original dial options and authentication behavior. The regression now observes asynchronous dial attempts, drives the client connection, and waits for connection state changes instead of sleeping. It fails if the injected dialer is called, including when initialization itself returns immediately. The client is closed on cleanup. No dependencies, recordings or production files are changed

Behavior change

Nothing changes for applications using the current release. VertexAI replay tests initialize and replay without access to an external endpoint. This revision addresses the test weakness raised in the review at #1548 (comment)

Testing Plan

Current tip: 5c83e4e. Merged current upstream main 44d41c9c1c48ee16d953e143a288b32972d84493; the contribution remains one test file

A local Go workspace contains the root and plugin/agentanalytics modules. With Go 1.27.1, go build -mod=readonly work passes, and go test -race -mod=readonly -count=1 -shuffle=on -timeout=120s work passes across 97 packages with tests. go mod tidy -diff is empty in both modules

With the project's Go 1.26.6 and CI-pinned golangci-lint v2.3.1, both modules report 0 issues. go test -race -mod=readonly -count=1 -shuffle=on ./session/vertexai/ also passes on Go 1.26.6. The machine's Go 1.27 export format was incompatible with the pinned analyzer, so lint was run with the project's declared toolchain. golangci-lint fmt --diff and git diff --check are clean

With the replay helper change reverted and the test kept: TestSetupReplay_InitializesWithoutExternalNetwork fails with the original blocking dial path. It also fails when replay keeps its interceptors but drops WithBlock and omits WithGRPCConn, the non-blocking regression identified in review

Blocking regression:
--- FAIL: TestSetupReplay_InitializesWithoutExternalNetwork (1.00s)
    replay client must initialize without a network connection: could not establish connection to the aiplatform server: context deadline exceeded

Non-blocking regression:
--- FAIL: TestSetupReplay_InitializesWithoutExternalNetwork (0.00s)
    replay client attempted a network connection

Restored implementation, Go 1.26.6:
ok  google.golang.org/adk/v2/session/vertexai  2.406s

The old regression was independently run against the same non-blocking mutant and passed, confirming that the added assertion addresses the reviewed gap. Both mutations were removed before final validation. An independent whole-diff review found no blocking issue

Integration limits

Existing RPC recordings exercise the service flows with UPDATE_REPLAYS unset. No live cloud E2E or re-recording was performed. As noted by the reviewer, the existing emptyService(..., offline=true) cases can still start background external connections; that separate behavior is unchanged and outside this PR's scope. Python parity is not applicable to this Go-specific replay harness, which changes no production API behavior

Checklist

• I have read CONTRIBUTING.md
• I have performed a self-review and an independent whole-diff review
• The regression rejects both blocking and non-blocking external-dial variants
• New and existing local tests pass across both modules
• Build, formatting, module tidy and CI-pinned lint pass
• Current-tip hosted CI and maintainer re-review are complete
• Live cloud end-to-end verification has been performed