test(ldap): sequence connection factory for failover tests

ZB.MOM.WW.Auth/tests/ZB.MOM.WW.Auth.Ldap.Tests/SequenceLdapConnectionFactory.cs

@@ -0,0 +1,51 @@
+using ZB.MOM.WW.Auth.Ldap.Internal;
+
+namespace ZB.MOM.WW.Auth.Ldap.Tests;
+
+/// <summary>
+/// Test double for <see cref="ILdapConnectionFactory"/> that hands out pre-scripted
+/// <see cref="FakeLdapConnection"/> instances in order, one per <see cref="Create"/> call —
+/// exactly matching the failover walk, which opens a fresh connection per endpoint attempt.
+/// Records every created connection for inspection. When the script runs out, returns a
+/// bare unscripted fake (which yields user-not-found) so a miscounted test fails loudly
+/// rather than reusing a stale fake.
+/// </summary>
+internal sealed class SequenceLdapConnectionFactory : ILdapConnectionFactory
+{
+    private readonly Queue<FakeLdapConnection> _script;
+
+    /// <summary>Scripts the connections handed out, in the order the walk will request them.</summary>
+    public SequenceLdapConnectionFactory(params FakeLdapConnection[] fakes)
+        => _script = new Queue<FakeLdapConnection>(fakes);
+
+    /// <summary>Every connection handed out, in creation order (scripted or overflow).</summary>
+    public List<FakeLdapConnection> Created { get; } = new();
+
+    /// <inheritdoc />
+    public ILdapConnection Create()
+    {
+        var fake = _script.Count > 0 ? _script.Dequeue() : new FakeLdapConnection();
+        Created.Add(fake);
+        return fake;
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Smoke test: verifies the sequencing and overflow behaviour the failover tests rely on.
+// ---------------------------------------------------------------------------
+
+public class SequenceLdapConnectionFactorySmokeTests
+{
+    [Fact]
+    public void Create_ReturnsScriptedFakesInOrder_ThenOverflows()
+    {
+        var first = new FakeLdapConnection().ThrowOnConnect();
+        var second = new FakeLdapConnection();
+        var factory = new SequenceLdapConnectionFactory(first, second);
+
+        Assert.Same(first, factory.Create());
+        Assert.Same(second, factory.Create());
+        Assert.NotSame(second, factory.Create()); // overflow: fresh bare fake
+        Assert.Equal(3, factory.Created.Count);
+    }
+}