feat(probe): S7 Test-Connect does a real ISO-on-TCP + S7 setup handshake

Replace bare TCP-connect with a two-phase probe: Phase 1 keeps the existing SocketException / timeout / generic preflight paths unchanged; Phase 2 runs Plc.OpenAsync (COTP CR/CC + S7 setup-communication) so a device that accepts TCP but is not an S7 PLC reads red instead of green. A linked CTS distinguishes caller cancellation ("timed out") from the S7netplus internal read-timeout OCE ("handshake failed: timed out").
2026-06-16 06:38:51 -04:00
parent 9b909002be
commit 9a8336ff6e
2 changed files with 190 additions and 7 deletions
@@ -0,0 +1,142 @@
+using System.Net;
+using System.Net.Sockets;
+using Shouldly;
+using Xunit;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.S7.Tests;
+
+/// <summary>
+///     Unit tests for <see cref="S7DriverProbe"/>. Uses in-process <see cref="TcpListener"/>
+///     instances on 127.0.0.1 to exercise all failure paths without a real PLC.
+///     The happy path (real S7 setup-communication exchange) is covered in live integration
+///     tests against a python-snap7 simulator.
+/// </summary>
+[Trait("Category", "Unit")]
+public sealed class S7DriverProbeTests
+{
+    private static readonly S7DriverProbe Probe = new();
+
+    // -------------------------------------------------------------------------
+    // 1. Invalid JSON
+    // -------------------------------------------------------------------------
+
+    /// <summary>Invalid JSON returns Ok=false with a message containing "invalid".</summary>
+    [Fact]
+    public async Task InvalidJson_Returns_OkFalse_WithInvalidMessage()
+    {
+        var result = await Probe.ProbeAsync(
+            "not-valid-json{{{",
+            TimeSpan.FromSeconds(3),
+            TestContext.Current.CancellationToken);
+
+        result.Ok.ShouldBeFalse();
+        result.Message.ShouldNotBeNull();
+        result.Message!.ToLowerInvariant().ShouldContain("invalid");
+        result.Latency.ShouldBeNull();
+    }
+
+    // -------------------------------------------------------------------------
+    // 2. Config with no host
+    // -------------------------------------------------------------------------
+
+    /// <summary>Config that serialises to null host returns Ok=false with a "no host/port" message.</summary>
+    [Fact]
+    public async Task NoHost_Returns_OkFalse_WithNoHostPortMessage()
+    {
+        // Host defaults to "127.0.0.1" in S7DriverOptions, but an empty string
+        // is what the spec's "no host" path covers. Provide an empty host explicitly.
+        var result = await Probe.ProbeAsync(
+            "{\"host\":\"\",\"port\":102}",
+            TimeSpan.FromSeconds(3),
+            TestContext.Current.CancellationToken);
+
+        result.Ok.ShouldBeFalse();
+        result.Message.ShouldNotBeNull();
+        result.Message!.ShouldContain("no host/port");
+        result.Latency.ShouldBeNull();
+    }
+
+    // -------------------------------------------------------------------------
+    // 3. Unreachable / refused port
+    // -------------------------------------------------------------------------
+
+    /// <summary>A closed port returns Ok=false with a "Connect failed" message.</summary>
+    [Fact]
+    public async Task ClosedPort_Returns_OkFalse_WithConnectFailedMessage()
+    {
+        // Bind a listener, read the OS-assigned port, then stop it so the port
+        // is guaranteed closed (no process listening) when the probe runs.
+        var reserved = new TcpListener(IPAddress.Loopback, 0);
+        reserved.Start();
+        var port = ((IPEndPoint)reserved.LocalEndpoint).Port;
+        reserved.Stop();
+
+        var configJson = $"{{\"host\":\"127.0.0.1\",\"port\":{port}}}";
+        var result = await Probe.ProbeAsync(
+            configJson,
+            TimeSpan.FromSeconds(3),
+            TestContext.Current.CancellationToken);
+
+        result.Ok.ShouldBeFalse();
+        result.Message.ShouldNotBeNull();
+        // SocketException maps to "Connect failed: <SocketErrorCode>" or similar.
+        result.Message!.ShouldContain("Connect failed");
+        result.Latency.ShouldBeNull();
+    }
+
+    // -------------------------------------------------------------------------
+    // 4. TCP accepts then immediately closes (non-S7 server)
+    // -------------------------------------------------------------------------
+
+    /// <summary>
+    ///     A listener that accepts the TCP connection and then immediately closes it without
+    ///     exchanging any bytes simulates a non-S7 server (wrong rack/slot, plain TCP echo,
+    ///     etc.). The probe must return Ok=false with a message containing "handshake failed".
+    ///     A short probe timeout (1 s) ensures the internal S7netplus socket-read timeout
+    ///     fires well within the test wall-clock budget of 10 s.
+    /// </summary>
+    [Fact]
+    public async Task TcpAcceptsThenCloses_Returns_OkFalse_WithHandshakeFailedMessage()
+    {
+        // Use a generous outer CTS so the test itself never races with the probe timeout.
+        using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(10));
+
+        var listener = new TcpListener(IPAddress.Loopback, 0);
+        listener.Start();
+        var port = ((IPEndPoint)listener.LocalEndpoint).Port;
+
+        // Accept one connection from the background and immediately close it —
+        // no S7 bytes exchanged, so OpenAsync must fail.
+        var serverTask = Task.Run(async () =>
+        {
+            try
+            {
+                using var client = await listener.AcceptTcpClientAsync(cts.Token);
+                // Immediately dispose → TCP RST/FIN; the S7 handshake receives nothing.
+            }
+            catch (OperationCanceledException) { /* test timed out */ }
+        }, cts.Token);
+
+        try
+        {
+            var configJson = $"{{\"host\":\"127.0.0.1\",\"port\":{port}}}";
+            // Pass a 1 s probe timeout so S7netplus's internal read-timeout fires quickly,
+            // and the 10 s outer CTS does NOT cancel first — the OCE will be from the
+            // internal handshakeCts, routing to the "handshake failed" branch.
+            var result = await Probe.ProbeAsync(
+                configJson,
+                TimeSpan.FromSeconds(1),
+                cts.Token);
+
+            result.Ok.ShouldBeFalse();
+            result.Message.ShouldNotBeNull();
+            result.Message!.ShouldContain("handshake failed");
+            result.Latency.ShouldBeNull();
+        }
+        finally
+        {
+            listener.Stop();
+            try { await serverTask; } catch { /* ignore */ }
+        }
+    }
+}