Auto: s7-c1 — surface negotiated PDU size via DriverHealth.Diagnostics

Closes #294

tests/ZB.MOM.WW.OtOpcUa.Driver.S7.IntegrationTests/S7_1500/S7_1500DiagnosticsTests.cs

@@ -0,0 +1,42 @@
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.S7.IntegrationTests.S7_1500;
+
+/// <summary>
+///     End-to-end coverage for the S7 driver's diagnostics surface against the python-snap7
+///     S7-1500 simulator. The simulator runs the upstream Snap7 server which negotiates a
+///     fixed 240-byte PDU during the COTP handshake; this suite asserts the driver captures
+///     and surfaces that value through <c>DriverHealth.Diagnostics["S7.NegotiatedPduSize"]</c>
+///     so the Admin UI driver-diagnostics panel can render it.
+/// </summary>
+[Collection(Snap7ServerCollection.Name)]
+[Trait("Category", "Integration")]
+[Trait("Device", "S7_1500")]
+public sealed class S7_1500DiagnosticsTests(Snap7ServerFixture sim)
+{
+    [Fact]
+    public async Task Driver_exposes_negotiated_pdu_size_post_init()
+    {
+        if (sim.SkipReason is not null) Assert.Skip(sim.SkipReason);
+
+        var options = S7_1500Profile.BuildOptions(sim.Host, sim.Port);
+        await using var drv = new S7Driver(options, driverInstanceId: "s7-pdu-diag");
+        await drv.InitializeAsync("{}", TestContext.Current.CancellationToken);
+
+        // Issue a read so BuildDiagnostics() flows into _health.Diagnostics through the
+        // Healthy state-transition (the post-OpenAsync construction also seeds it, but we
+        // exercise the read path too so the assertion is robust against future refactors
+        // that move the seed point).
+        var snapshots = await drv.ReadAsync(
+            [S7_1500Profile.ProbeTag], TestContext.Current.CancellationToken);
+        snapshots[0].StatusCode.ShouldBe(0u, "probe read must succeed before checking diagnostics");
+
+        var diagnostics = drv.GetHealth().DiagnosticsOrEmpty;
+        diagnostics.ContainsKey("S7.NegotiatedPduSize").ShouldBeTrue(
+            "S7 driver must surface negotiated PDU size as S7.NegotiatedPduSize");
+        diagnostics["S7.NegotiatedPduSize"].ShouldBeGreaterThan(0,
+            "Snap7 negotiates a 240-byte PDU on every COTP handshake — anything ≤ 0 means the snapshot was missed");
+    }
+}