feat: advance legacy UI behavior parity

tests/MBN_STOCK_WEBVIEW.LegacyApplication.Tests/Comparison/LegacyComparisonWorkflowTests.cs

@@ -221,6 +221,111 @@ public sealed class LegacyComparisonWorkflowTests
         Assert.False(snapshot.IsBusy);
     }
 
+    [Fact]
+    public async Task Uc3_AllowsExactDuplicatePairsAndMovesOrDeletesOnlyTheSelectedStableRow()
+    {
+        var data = new FakeDataService { DomesticResults = [Samsung, SkHynix] };
+        var store = new FakePairStore();
+        var controller = CreateController(data, store);
+        var search = await controller.SearchDomesticAsync(string.Empty);
+        controller.ChooseDomesticResult(search.DomesticSearch.Results[0].SelectionId);
+        controller.ChooseDomesticResult(search.DomesticSearch.Results[1].SelectionId);
+
+        var firstAdd = await controller.AddDraftPairAsync();
+        var firstRowId = Assert.Single(firstAdd.SavedPairs).RowId;
+        var secondAdd = await controller.AddDraftPairAsync();
+        var secondRowId = secondAdd.SavedPairs[1].RowId;
+
+        Assert.NotEqual(firstRowId, secondRowId);
+        Assert.Equal(
+            new[] { firstRowId, secondRowId },
+            secondAdd.SavedPairs.Select(pair => pair.RowId));
+        Assert.All(
+            secondAdd.SavedPairs,
+            pair => Assert.Equal("SK하이닉스 ↔ 삼성전자", pair.DisplayLabel));
+        Assert.Collection(
+            store.Writes[^1],
+            row => Assert.Equal(
+                new LegacyComparisonPairWriteRow(
+                    1,
+                    "SK하이닉스",
+                    "코스피",
+                    "삼성전자",
+                    "코스피"),
+                row),
+            row => Assert.Equal(
+                new LegacyComparisonPairWriteRow(
+                    2,
+                    "SK하이닉스",
+                    "코스피",
+                    "삼성전자",
+                    "코스피"),
+                row));
+
+        controller.SelectSavedPair(secondRowId);
+        var moved = await controller.MoveSelectedPairAsync(
+            LegacyComparisonPairMoveDirection.Up);
+
+        Assert.Equal(
+            new[] { secondRowId, firstRowId },
+            moved.SavedPairs.Select(pair => pair.RowId));
+        Assert.Equal(secondRowId, moved.SelectedPairId);
+        Assert.True(moved.SavedPairs[0].IsSelected);
+        Assert.False(moved.SavedPairs[1].IsSelected);
+
+        var deleted = await controller.DeleteSelectedPairAsync();
+
+        var remaining = Assert.Single(deleted.SavedPairs);
+        Assert.Equal(firstRowId, remaining.RowId);
+        Assert.True(remaining.IsSelected);
+        Assert.Equal(firstRowId, deleted.SelectedPairId);
+        Assert.Single(store.Writes[^1]);
+    }
+
+    [Fact]
+    public async Task Uc3_DuplicatePairSaveRoundTripPreservesPhysicalRowOrder()
+    {
+        var data = new FakeDataService();
+        data.Resolve(Samsung, "삼성전자", "코스피");
+        data.Resolve(SkHynix, "SK하이닉스", "코스피");
+        data.Resolve(Apple, "APPLE", string.Empty);
+        var store = new FakePairStore
+        {
+            Bytes = EncodeCp949(
+                ("삼성전자", "코스피", "SK하이닉스", "코스피"),
+                ("삼성전자", "코스피", "SK하이닉스", "코스피"),
+                ("코스피 지수", string.Empty, "APPLE", string.Empty))
+        };
+        var controller = CreateController(data, store);
+        var loaded = await controller.LoadSavedPairsAsync();
+        var thirdRowId = loaded.SavedPairs[2].RowId;
+        controller.SelectSavedPair(thirdRowId);
+
+        var moved = await controller.MoveSelectedPairAsync(
+            LegacyComparisonPairMoveDirection.Up);
+
+        Assert.Equal(
+            new[]
+            {
+                "삼성전자 ↔ SK하이닉스",
+                "코스피 지수 ↔ APPLE",
+                "삼성전자 ↔ SK하이닉스"
+            },
+            moved.SavedPairs.Select(pair => pair.DisplayLabel));
+        Assert.Equal(new[] { 1, 2, 3 }, store.Writes[^1].Select(row => row.RowNumber));
+
+        var reloadedStore = new FakePairStore
+        {
+            Bytes = EncodeCp949(store.Writes[^1])
+        };
+        var reloaded = await CreateController(data, reloadedStore).LoadSavedPairsAsync();
+
+        Assert.Equal(
+            moved.SavedPairs.Select(pair => pair.DisplayLabel),
+            reloaded.SavedPairs.Select(pair => pair.DisplayLabel));
+        Assert.Equal(3, reloaded.SavedPairs.Select(pair => pair.RowId).Distinct().Count());
+    }
+
     [Fact]
     public async Task SavedPairMoveAndDelete_PreserveActiveRowAndPersistPhysicalOrder()
     {
@@ -424,6 +529,13 @@ public sealed class LegacyComparisonWorkflowTests
         return encoding.GetBytes(string.Join("\r\n", lines) + "\r\n");
     }
 
+    private static byte[] EncodeCp949(IReadOnlyList<LegacyComparisonPairWriteRow> rows) =>
+        EncodeCp949(rows.Select(row => (
+            row.FirstName,
+            row.FirstMarket,
+            row.SecondName,
+            row.SecondMarket)).ToArray());
+
     private sealed class FakeDataService : ILegacyComparisonDataService
     {
         private readonly Dictionary<LegacyComparisonStoredTargetReference, LegacyComparisonTarget>