lmxopcua/tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests/ContractsIsDependencyLightTests.cs

using Shouldly;
using Xunit;

namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests;

/// <summary>
///     Pins the dependency shape of <c>ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Contracts</c>: it must not
///     reference the OPC UA client SDK.
///     <para>
///         <b>Why this matters beyond tidiness.</b> Deferment-register G-7 wired
///         <see cref="OpcUaClientTagDefinitionFactory.Inspect"/> into the deploy-time TagConfig gate, which
///         made <c>ControlPlane</c> project-reference this Contracts assembly. ControlPlane is loaded by
///         every admin- and driver-role host, so whatever Contracts drags in, they all carry. Contracts
///         used to hold <c>NamespaceMap</c> — <c>ISession</c>/<c>NodeId</c>-typed throughout — and with it a
///         <c>OPCFoundation.NetStandard.Opc.Ua.Client</c> PackageReference; NamespaceMap moved to the
///         sibling <c>.Session</c> leaf so the parse-only half could stay light (the same shape as
///         <c>Calculation.Contracts</c>: Core.Abstractions and nothing else).
///     </para>
///     <para>
///         <b>Direction matters: this is an ABSENCE assertion, and that is what makes it sound here.</b>
///         The assembly manifest is an unreliable witness for PRESENCE — the C# compiler elides a reference
///         nothing in the IL actually uses, so "assembly X is referenced" can be false while the csproj says
///         otherwise (the trap <c>EquipmentTagConfigInspectorCoverageTests</c> documents, which is why that
///         one scans the output directory instead). Absence has no such hole in the direction that matters:
///         the moment someone adds Opc.Ua-typed code to Contracts, the compiler MUST emit the reference and
///         this test goes red. A csproj PackageReference that nothing consumes is elided and slips past —
///         accepted deliberately, because an unused package reference is not the failure being guarded.
///     </para>
///     <para>
///         Falsified 2026-08-09 by temporarily adding an <c>Opc.Ua.NodeId</c>-typed member to Contracts:
///         the assertion failed naming <c>Opc.Ua.Core</c>, and passed again once removed.
///     </para>
/// </summary>
public sealed class ContractsIsDependencyLightTests
{
    /// <summary>The Contracts assembly's manifest must name no OPC UA SDK assembly.</summary>
    [Fact]
    public void The_Contracts_assembly_does_not_reference_the_OPC_UA_SDK()
    {
        var contracts = typeof(OpcUaClientTagDefinitionFactory).Assembly;

        // Positive control: name the assembly under test, so a rename/retarget cannot silently point this
        // at something else that trivially satisfies the assertion below.
        contracts.GetName().Name.ShouldBe("ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Contracts");

        var opcUa = contracts.GetReferencedAssemblies()
            .Select(a => a.Name ?? string.Empty)
            .Where(n => n.StartsWith("Opc.Ua", StringComparison.OrdinalIgnoreCase))
            .OrderBy(n => n, StringComparer.Ordinal)
            .ToArray();

        opcUa.ShouldBeEmpty(
            "OpcUaClient.Contracts must stay free of the OPC UA client SDK — ControlPlane project-references "
            + "it for the G-7 deploy-time TagConfig gate, so every host that loads the control plane would "
            + "carry the stack. Put SDK-typed code in Driver.OpcUaClient.Session instead. Found: "
            + string.Join(", ", opcUa));
    }

    /// <summary>
    ///     The counterpart the assertion above is meaningful against: the SDK-typed half really did land
    ///     somewhere, and that somewhere does reference the SDK. Without this, "no Opc.Ua reference
    ///     anywhere" would read as a pass.
    /// </summary>
    [Fact]
    public void The_Session_assembly_is_where_the_OPC_UA_SDK_reference_lives()
    {
        var session = typeof(NamespaceMap).Assembly;

        session.GetName().Name.ShouldBe("ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Session");
        session.GetReferencedAssemblies()
            .Select(a => a.Name ?? string.Empty)
            .ShouldContain(n => n.StartsWith("Opc.Ua", StringComparison.OrdinalIgnoreCase));
    }
}