test(grpc): write-reuse + read-on-write-session probe (one-vs-two-kind decider)

tests/AVEVA.Historian.Client.Tests/HandshakeReuseSpikeTests.cs

@@ -1,6 +1,7 @@
 using System.Diagnostics;
 using AVEVA.Historian.Client.Grpc;
 using AVEVA.Historian.Client.Models;
+using AVEVA.Historian.Client.Wcf;
 using Xunit.Abstractions;
 
 namespace AVEVA.Historian.Client.Tests;
@@ -110,8 +111,70 @@ public sealed class HandshakeReuseSpikeTests
         }
     }
 
+    // (A) WRITE REUSE VALIDITY: one externally-opened 0x401 (write-enabled) session, N writes on it via
+    // RunWriteOnSession — NO Create()/handshake per write. If the server rejects reusing a write session,
+    // write #2 throws -> RED finding. Both succeed -> GREEN (write-reuse is sound). Bounded writes to the
+    // sandbox tag ONLY; latency LOGGED, success ASSERTED.
+    [Fact]
+    public void WriteEnabledSession_RunsTwoWrites_AllSucceed()
+    {
+        if (!TryGetWriteEnv(out string host, out string sandboxTag)) return;
+        HistorianClientOptions options = BuildOptions(host);
+        using HistorianGrpcConnection connection = HistorianGrpcChannelFactory.Create(options);
+        HistorianGrpcHandshake.Session session = OpenWriteSession(options, connection);
+        var writer = new HistorianGrpcHistoricalWriteOrchestrator(options);
+
+        for (int i = 0; i < 2; i++)
+        {
+            var sw = Stopwatch.StartNew();
+            bool ok = writer.RunWriteOnSession(connection, session, sandboxTag,
+                new[] { new HistorianHistoricalValue(DateTime.UtcNow.AddSeconds(-i), 1.0 + i, OpcQuality: 192) },
+                CancellationToken.None);
+            sw.Stop();
+            _output.WriteLine($"reused-write[{i}] = {sw.ElapsedMilliseconds} ms, ok={ok}");
+            Assert.True(ok);
+        }
+    }
+
+    // (B) READ-ON-WRITE-SESSION PROBE: can a 0x401 (write-enabled) session ALSO serve a raw read? Decides
+    // the pool shape — ONE-KIND (a single write-enabled session serves both reads and writes) vs TWO-KIND
+    // (separate read 0x402 / write 0x401 sessions). The kind is LOGGED, never asserted; any failure is
+    // swallowed (a rejection is itself the finding, not a test failure). READ-ONLY here.
+    [Fact]
+    public void WriteEnabledSession_AlsoServesRead_RecordsKind()
+    {
+        if (!TryGetWriteEnv(out string host, out string sandboxTag)) return;
+        HistorianClientOptions options = BuildOptions(host);
+        using HistorianGrpcConnection connection = HistorianGrpcChannelFactory.Create(options);
+        HistorianGrpcHandshake.Session session = OpenWriteSession(options, connection);
+        (DateTime startUtc, DateTime endUtc) = LastSevenDays();
+        try
+        {
+            List<HistorianSample> rows = new HistorianGrpcReadOrchestrator(options)
+                .RunRawQueryOnSession(connection, session.ClientHandle, sandboxTag, startUtc, endUtc, 8, CancellationToken.None);
+            _output.WriteLine($"read-on-0x401 -> OK (rows={rows.Count}) => ONE-KIND pool (write-enabled serves reads)");
+        }
+        catch (Exception ex)
+        {
+            _output.WriteLine($"read-on-0x401 -> FAILED ({ex.GetType().Name}) => TWO-KIND pool (separate read/write)");
+        }
+    }
+
     // --- helpers ---
 
+    private static bool TryGetWriteEnv(out string host, out string sandboxTag)
+    {
+        host = Environment.GetEnvironmentVariable("HISTORIAN_GRPC_HOST") ?? "";
+        sandboxTag = Environment.GetEnvironmentVariable("HISTORIAN_WRITE_SANDBOX_TAG") ?? "";
+        return !string.IsNullOrWhiteSpace(host)
+            && !string.IsNullOrWhiteSpace(sandboxTag)
+            && !string.IsNullOrEmpty(Environment.GetEnvironmentVariable("HISTORIAN_USER"));
+    }
+
+    private static HistorianGrpcHandshake.Session OpenWriteSession(HistorianClientOptions o, HistorianGrpcConnection c)
+        => HistorianGrpcHandshake.OpenSession(c, o, CancellationToken.None,
+            connectionMode: HistorianWcfAuthChainHelper.NativeIntegratedWriteEnabledConnectionMode);
+
     private static bool TryGetEnv(out string host, out string tag)
     {
         host = Environment.GetEnvironmentVariable("HISTORIAN_GRPC_HOST") ?? "";