refactor: share in-memory gRPC bufconn helpers across fake-RPC tests

[apstndb]

Summary

Shared in-memory gRPC transport helpers for fake Spanner and DatabaseAdmin servers. Each test keeps its own fake-server behavior; heartbeatRPCServer is not turned into a universal fake. Real TCP/TLS fixtures in tls_transport_test.go and spanner_metrics_test.go are unchanged.

Lifecycle review of the U1 prototype:

• Dialer keeps listener.Dial() rather than DialContext. No migrated test covers cancelled-dial behavior, and RecreateClient / USE / DETACH still dial the shared listener after t.Context() is cancelled during cleanup.
• Serve errors are reported inside t.Cleanup after Stop returns, so a Serve goroutine cannot log after cleanup completes.
• No fixed sleeps.

#1018 was still open and unmerged at publication, so this branch is based on current origin/main without that execute_sql_test.go change. Merge main additively if #1018 lands first.

Base / HEAD

• Base: cbc1663366464409aba93f0d82cff9f4e9daa87b (origin/main)
• HEAD: d716daca8d53d61e3e809c5d5135f32965e6ef19

Numstat

Kind	Files	+	−	Net
Production	0	0	0	0
Test callers	16	33	590	−557
Fixture helper (internal/mycli/bufconn_test.go)	1	171	0	+171
Combined test/fixture	17	204	590	−386

Per-file:

171  0  internal/mycli/bufconn_test.go
  1 35  internal/mycli/ddl_in_transaction_rpc_test.go
  4 25  internal/mycli/directed_read_matrix_test.go
  7 32  internal/mycli/directed_read_wire_test.go
  1 42  internal/mycli/execute_ddl_rpc_test.go
  1 36  internal/mycli/execute_ddl_sequence_kind_rpc_test.go
  1 31  internal/mycli/execute_partitioned_test.go
  1 41  internal/mycli/execute_sql_test.go
  3 62  internal/mycli/fuzzy_finder_candidates_test.go
  3 26  internal/mycli/heartbeat_owner_test.go
  1 43  internal/mycli/query_cache_test.go
  3 37  internal/mycli/show_operation_test.go
  1 41  internal/mycli/statements_query_profile_test.go
  3 21  internal/mycli/statements_run_partition_test.go
  1 43  internal/mycli/stream_width_test.go
  1 42  internal/mycli/string_quote_stream_test.go
  1 33  internal/mycli/sync_proto_bundle_test.go

Eliminated RPC setup is the repeated bufconn.Listen / Serve / grpc.NewClient / client-construction blocks. Retained real integration: TCP listeners in tls_transport_test.go, spanner_metrics_test.go, and the partition TCP fixture in statements_run_partition_test.go.

Scenario mapping

No named Test* functions were added or removed. Every previously named case survives under the same name. Collapsed transport setup maps as follows:

Removed local transport setup	Surviving named cases / remaining constructor
newQueryCacheRPCSession bufconn bootstrap	TestQueryCachePublication* via newBufconnQuerySession
newEmptySQLRPCSession bufconn bootstrap	TestExecuteSQLBufferedAndStreamingEmptyResults via newBufconnQuerySession
stream-width / string-quote / query-profile session bootstrap	TestTablePreviewProcessorStreamingPreservesValue, TestExecuteSQLStreamingTablePreservesValue, TestCLIStringQuoteModeStreaming*, TestShowQueryProfile* via newBufconnQuerySession
newDDLAdminSession / newScriptedDDLSession / attachDDLAdmin	TestExecuteDdlStatementsRPC, TestSequenceKindRepairRPC, TestDDLInTransaction* via newBufconnAdminSession / newBufconnAdminClient
sync_proto_bundle admin attach	TestSyncProtoBundle* via newBufconnAdminClient
newShowOperationTestSession (Operations only; bare systemVariables)	TestShowOperation* via dialBufconn
newFuzzyAdminSession / newFuzzySchemaSession (p/i/db identity kept)	TestFetchAdminCandidates, TestFetchSchemaObjectCandidates, other TestFuzzy* / TestFetch* / TestResolveCandidates*
startDirectedReadWire / startDirectedReadDial / run-partition dial options	TestDirectedRead*, TestRunPartition*, TestPartitionExportsCompleteEnvelope via newBufconnSpannerClient / bufconnClientOptions
startPartitionFanIn	TestRunPartitioned*, TestStreamPartitioned*, TestBufferPartitioned* via newBufconnSpannerClient
newHeartbeatHarness listener/server (custom clientOpts kept)	TestHeartbeat* via dialBufconn; heartbeatRPCServer unchanged

Gates

Captured under .worktrees/test-bufconn-helper/.tmp/quality-wave-20260917/ at HEAD d716daca8d53d61e3e809c5d5135f32965e6ef19:

1. Migrated test families (go test -short -count=1 ./internal/mycli with the 109 surviving names): exit 0
2. GOTOOLCHAIN=go1.26.8 make check with golangci-lint 2.13.2: exit 0
3. GOTOOLCHAIN=go1.26.8 make check-race: exit 0

Environment: GOTOOLCHAIN=go1.26.8, Homebrew golangci-lint 2.13.2, DOCKER_HOST=unix:///Users/apstndb/.colima/default/docker.sock, TESTCONTAINERS_DOCKER_SOCKET_OVERRIDE=/var/run/docker.sock.

  

[github-actions]

Code Metrics Report

📊 View detailed coverage report (available for 7 days)

	main (f86e0d2)	#1021 (becd62d)	+/-
Coverage	87.4%	87.4%	0.0%
Code to Test Ratio	1:2.5	1:2.5	-0.1
Test Execution Time	2m50s	2m40s	-10s

Details

  |                     | main (f86e0d2) | #1021 (becd62d) | +/-  |
  |---------------------|----------------|-----------------|------|
  | Coverage            |          87.4% |           87.4% | 0.0% |
  |   Files             |            132 |             132 |    0 |
  |   Lines             |          13294 |           13294 |    0 |
  |   Covered           |          11629 |           11629 |    0 |
- | Code to Test Ratio  |          1:2.5 |           1:2.5 | -0.1 |
  |   Code              |          28902 |           28902 |    0 |
- |   Test              |          73163 |           72726 | -437 |
+ | Test Execution Time |          2m50s |           2m40s | -10s |

---

Reported by octocov

[apstndb]

Reviewed HEAD d716daca8d53d61e3e809c5d5135f32965e6ef19: no actionable findings in this diff.

Reviewed all migrated fixtures and the shared transport cleanup order, Serve completion, service registration, and per-client options. The existing dial behavior and separate TCP/TLS fixtures are preserved.

Current hosted CI checks pass. This is a source-review conclusion for this HEAD; the PR remains draft pending integration.

[apstndb]

Reviewed updated HEAD cde96d0ba76c36fb379608c7c0865d5e2cc2fa91: no actionable findings.

The tree exactly matches the clean automatic merge of the previously reviewed change with main f86e0d2e8513679d9ce7f0b45bde86565d81f8dc. The remaining PR diff preserves the accepted behavior; no conflict resolution or additional change was introduced. The local make check passed for this integrated tree. Hosted checks for this exact HEAD remain the merge gate.