Phase 3 PR 36 — AVEVA prerequisites test-support library. New tests/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.TestSupport multi-targeted class library (net10.0 + net48 so both the modern and the MXAccess-COM x86 test projects can consume it) that probes every piece of the AVEVA System Platform + OtOpcUa stack a live-Galaxy test depends on and returns a structured PrerequisiteReport. Closes the gap where live-smoke tests silently returned 'unreachable' without telling operators which specific piece failed.

AvevaPrerequisites.CheckAllAsync walks eight probe categories producing PrerequisiteCheck rows each with Name (e.g. 'service:aaBootstrap', 'sql:ZB', 'com:LMXProxy', 'registry:ArchestrA.Framework'), Category (AvevaCoreService / AvevaSoftService / AvevaInstall / MxAccessCom / GalaxyRepository / AvevaHistorian / OtOpcUaService / Environment), Status (Pass / Warn / Fail / Skip), and operator-facing Detail message. Report aggregates them: IsLivetestReady (no Fails anywhere) and IsAvevaSideReady (AVEVA-side categories pass, our v2 services can be absent while still considering the environment AVEVA-ready) so different test tiers can use the right threshold.
Individual probes: ServiceProbe.Check queries the Windows Service Control Manager via System.ServiceProcess.ServiceController — treats DemandStart+Stopped as Warn (NmxSvc is DemandStart by design; master pulls it up) but AutoStart+Stopped as Fail; not-installed is Fail for hard-required services, Warn for soft ones; non-Windows hosts get Skip; transitional states like StartPending get Warn with a 'try again' hint. RegistryProbe reads HKLM\SOFTWARE\WOW6432Node\ArchestrA\{Framework,Framework\Platform,MSIInstall} — Framework key presence + populated InstallPath/RootPath values mean System Platform installed; PfeConfigOptions in the Platform subkey (format 'PlatformId=N,EngineId=N,...') indicates a Platform has been deployed from the IDE (PlatformId=0 means never deployed — MXAccess will connect but every subscription will be Bad quality); RebootRequired='True' under MSIInstall surfaces as a loud warn since post-patch behavior is undefined. MxAccessComProbe resolves the LMXProxy.LMXProxyServer ProgID → CLSID → HKLM\SOFTWARE\Classes\WOW6432Node\CLSID\{guid}\InprocServer32, verifying the registered file exists on disk (catches the orphan-registry case where a previous uninstall left the ProgID registered but the DLL is gone — distinguishes it from the 'totally not installed' case by message); also emits a Warn when the test process is 64-bit (MXAccess COM activation fails with REGDB_E_CLASSNOTREG 0x80040154 regardless of registration, so seeing this warning tells operators why the activation would fail even on a fully-installed machine). SqlProbe tests Galaxy Repository via Microsoft.Data.SqlClient using the Windows-auth localhost connection string the repo code defaults to — distinguishes 'SQL Server unreachable' (connection fails) from 'ZB database does not exist' (SELECT DB_ID('ZB') returns null) because they have different remediation paths (sc.exe start MSSQLSERVER vs. restore from .cab backup); a secondary CheckDeployedObjectCountAsync query on 'gobject WHERE deployed_version > 0' warns when the count is zero because discovery smoke tests will return empty hierarchies. NamedPipeProbe opens a 2s NamedPipeClientStream against OtOpcUaGalaxyHost's pipe ('OtOpcUaGalaxy' per the installer default) — pipe accepting a connection proves the Host service is listening; disconnects immediately so we don't consume a session slot.
Service lists kept as internal static data so tests can inspect + override: CoreServices (aaBootstrap + aaGR + NmxSvc + MSSQLSERVER — hard fail if missing), SoftServices (aaLogger + aaUserValidator + aaGlobalDataCacheMonitorSvr — warn only; stack runs without them but diagnostics/auth are degraded), HistorianServices (aahClientAccessPoint + aahGateway — opt-in via Options.CheckHistorian, only matters for HistoryRead IPC paths), OtOpcUaServices (our OtOpcUaGalaxyHost hard-required for end-to-end live tests + OtOpcUa warn + GLAuth warn). Narrower entry points CheckRepositoryOnlyAsync and CheckGalaxyHostPipeOnlyAsync for tests that only care about specific subsystems — avoid paying the full probe cost on every GalaxyRepositoryLiveSmokeTests fact.
Multi-targeting mechanics: System.ServiceProcess.ServiceController + Microsoft.Win32.Registry are NuGet packages on net10 but in-box BCL references on net48; csproj conditions Package vs Reference by TargetFramework. Microsoft.Data.SqlClient v6 supports both frameworks so single PackageReference. Net48Polyfills.cs provides IsExternalInit shim (records/init-only setters) and SupportedOSPlatformAttribute stub so the same Probe sources compile on both frameworks without per-callsite preprocessor guards — lets Roslyn's platform-compatibility analyzer stay useful on net10 without breaking net48 builds.
Existing GalaxyRepositoryLiveSmokeTests updated to delegate its skip decision to AvevaPrerequisites.CheckRepositoryOnlyAsync (legacy ZbReachableAsync kept as a compatibility adapter so the in-test 'if (!await ZbReachableAsync()) return;' pattern keeps working while the surrounding fixtures gradually migrate to Assert.Skip-with-reason). Slnx file registers the new project.
Tests — AvevaPrerequisitesLiveTests (8 new Integration cases, Category=LiveGalaxy): the helper correctly reports Framework install (registry pass), aaBootstrap Running (service pass), aaGR Running (service pass), MxAccess COM registered (com pass), ZB database reachable (sql pass), deployed-object count > 0 (warn-upgraded-to-pass because this box has 49 objects deployed), the AVEVA side is ready even when our own services (OtOpcUaGalaxyHost) aren't installed yet (IsAvevaSideReady=true), and the helper emits rows for OtOpcUaGalaxyHost + OtOpcUa + GLAuth even when not installed (regression guard — nobody can accidentally ship a check that omits our own services). Full Galaxy.Host.Tests Category=LiveGalaxy suite: 13 pass (5 prior smoke + 8 new prerequisites). Full solution build clean, 0 errors.
What's NOT in this PR: end-to-end Galaxy stack smoke (Proxy → Host pipe → MXAccess → real Galaxy tag). That's the next PR — this one is the gate the end-to-end smoke will call first to produce actionable skip messages instead of silent returns.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/ZB.MOM.WW.OtOpcUa.Driver.Galaxy.TestSupport/PrerequisiteReport.cs

@@ -0,0 +1,94 @@
+using System.Text;
+
+namespace ZB.MOM.WW.OtOpcUa.Driver.Galaxy.TestSupport;
+
+/// <summary>
+///     Aggregated result of an <see cref="AvevaPrerequisites.CheckAll"/> run. Test fixtures
+///     typically call <see cref="SkipReason"/> to produce the argument for xUnit's
+///     <c>Assert.Skip</c> when any hard dependency failed.
+/// </summary>
+public sealed class PrerequisiteReport
+{
+    public IReadOnlyList<PrerequisiteCheck> Checks { get; }
+
+    public PrerequisiteReport(IEnumerable<PrerequisiteCheck> checks)
+    {
+        Checks = [.. checks];
+    }
+
+    /// <summary>True when every probe is Pass / Warn / Skip — no Fail entries.</summary>
+    public bool IsLivetestReady => !Checks.Any(c => c.Status == PrerequisiteStatus.Fail);
+
+    /// <summary>
+    ///     True when only the AVEVA-side probes pass — ignores failures in the
+    ///     <see cref="PrerequisiteCategory.OtOpcUaService"/> category. Lets a live-test gate
+    ///     say "AVEVA is ready even if the v2 services aren't installed yet" without
+    ///     conflating the two. Useful for tests that exercise Galaxy directly (e.g.
+    ///     <see cref="GalaxyRepositoryLiveSmokeTests"/>) rather than through our stack.
+    /// </summary>
+    public bool IsAvevaSideReady =>
+        !Checks.Any(c => c.Status == PrerequisiteStatus.Fail && c.Category != PrerequisiteCategory.OtOpcUaService);
+
+    /// <summary>
+    ///     Multi-line message for <c>Assert.Skip</c> when a hard dependency isn't met. Returns
+    ///     null when <see cref="IsLivetestReady"/> is true.
+    /// </summary>
+    public string? SkipReason
+    {
+        get
+        {
+            var fails = Checks.Where(c => c.Status == PrerequisiteStatus.Fail).ToList();
+            if (fails.Count == 0) return null;
+
+            var sb = new StringBuilder();
+            sb.AppendLine($"Live-AVEVA prerequisites not met ({fails.Count} failed):");
+            foreach (var f in fails)
+                sb.AppendLine($"  • [{f.Category}] {f.Name} — {f.Detail}");
+            sb.Append("Run `Get-Service aa*` / `sqlcmd -S localhost -d ZB -E -Q \"SELECT 1\"` to triage.");
+            return sb.ToString();
+        }
+    }
+
+    /// <summary>
+    ///     Human-readable summary of warnings — caller decides whether to log or ignore. Useful
+    ///     when a live test does pass but an operator should know their environment is degraded.
+    /// </summary>
+    public string? Warnings
+    {
+        get
+        {
+            var warns = Checks.Where(c => c.Status == PrerequisiteStatus.Warn).ToList();
+            if (warns.Count == 0) return null;
+
+            var sb = new StringBuilder();
+            sb.AppendLine($"AVEVA prerequisites with warnings ({warns.Count}):");
+            foreach (var w in warns)
+                sb.AppendLine($"  • [{w.Category}] {w.Name} — {w.Detail}");
+            return sb.ToString();
+        }
+    }
+
+    /// <summary>
+    ///     Throw <see cref="InvalidOperationException"/> if any <paramref name="categories"/>
+    ///     contain a Fail — useful when a specific test needs, say, Galaxy Repository but doesn't
+    ///     care about Historian. Call before <c>Assert.Skip</c> if you want to be strict.
+    /// </summary>
+    public void RequireCategories(params PrerequisiteCategory[] categories)
+    {
+        var set = categories.ToHashSet();
+        var fails = Checks.Where(c => c.Status == PrerequisiteStatus.Fail && set.Contains(c.Category)).ToList();
+        if (fails.Count == 0) return;
+
+        var detail = string.Join("; ", fails.Select(f => $"{f.Name}: {f.Detail}"));
+        throw new InvalidOperationException($"Required prerequisite categories failed: {detail}");
+    }
+
+    public override string ToString()
+    {
+        var sb = new StringBuilder();
+        sb.AppendLine($"PrerequisiteReport: {Checks.Count} checks");
+        foreach (var c in Checks)
+            sb.AppendLine($"  [{c.Status,-4}] {c.Category}/{c.Name}: {c.Detail}");
+        return sb.ToString();
+    }
+}