batch37 task6 implement group E pre-ack snapshot and restore

dotnet/tests/ZB.MOM.NatsNet.Server.Tests/Accounts/AccountStreamRestoreTests.cs

@@ -0,0 +1,33 @@
+using Shouldly;
+using ZB.MOM.NatsNet.Server;
+
+namespace ZB.MOM.NatsNet.Server.Tests.Accounts;
+
+public sealed class AccountStreamRestoreTests
+{
+    [Fact]
+    public void RestoreStream_EmptySnapshot_ReturnsError()
+    {
+        var account = new Account { Name = "A" };
+        var config = new StreamConfig { Name = "S", Storage = StorageType.MemoryStorage };
+
+        var (stream, error) = account.RestoreStream(config, new MemoryStream());
+
+        stream.ShouldBeNull();
+        error.ShouldNotBeNull();
+    }
+
+    [Fact]
+    public void RestoreStream_WithSnapshotData_AddsStream()
+    {
+        var account = new Account { Name = "A" };
+        var config = new StreamConfig { Name = "S", Storage = StorageType.MemoryStorage };
+        using var snapshot = new MemoryStream([1, 2, 3]);
+
+        var (stream, error) = account.RestoreStream(config, snapshot);
+
+        error.ShouldBeNull();
+        stream.ShouldNotBeNull();
+        stream!.Name.ShouldBe("S");
+    }
+}