test: foreach enumerator coverage for mixed group + varData (#156 follow-up)

tests/SbeCodeGenerator.IntegrationTests/GroupForeachWithVarDataTests.cs

@@ -0,0 +1,95 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Xunit;
+using NO = Cross.Schema.Orders.V0.NewOrderData;
+
+namespace SbeCodeGenerator.IntegrationTests
+{
+    /// <summary>
+    /// Issue #156 follow-up: coverage for the mixed scenario — message with
+    /// simple top-level groups AND top-level varData. The foreach API must be
+    /// emitted for the groups (since they're simple), independent of the varData
+    /// that follows them. ReadGroups continues to work for both.
+    /// </summary>
+    public class GroupForeachWithVarDataTests
+    {
+        private static byte[] Encode(NO order, NO.LegsData[] legs, string clientOrderId)
+        {
+            var buffer = new byte[1024];
+            var coid = Encoding.UTF8.GetBytes(clientOrderId);
+            Assert.True(NO.TryEncode(order, buffer, legs, coid, out int written));
+            Array.Resize(ref buffer, written);
+            return buffer;
+        }
+
+        [Fact]
+        public void Foreach_OnSimpleGroup_WhenMessageAlsoHasTopLevelVarData()
+        {
+            var order = new NO { OrderId = 42, Quantity = 100, Side = Cross.Schema.Orders.V0.Side.Buy };
+            var legs = new[]
+            {
+                new NO.LegsData { LegSymbol = 1, LegRatio = 1, LegSide = Cross.Schema.Orders.V0.Side.Buy },
+                new NO.LegsData { LegSymbol = 2, LegRatio = 2, LegSide = Cross.Schema.Orders.V0.Side.Sell },
+                new NO.LegsData { LegSymbol = 3, LegRatio = 3, LegSide = Cross.Schema.Orders.V0.Side.Buy },
+            };
+            var buffer = Encode(order, legs, "CLIENT-ORDER-XYZ");
+
+            Assert.True(NO.TryParse(buffer, out var reader));
+
+            var symbols = new List<uint>();
+            foreach (ref readonly var leg in reader.Legs)
+                symbols.Add(leg.LegSymbol);
+
+            Assert.Equal(new uint[] { 1, 2, 3 }, symbols);
+        }
+
+        [Fact]
+        public void Foreach_DoesNotConsumeVarData_ReadGroupsStillWorks()
+        {
+            // After foreach iterating Legs, the top-level ClientOrderId varData
+            // must still be reachable via ReadGroups (which scans from _blockLength
+            // through its own SpanReader — independent of the foreach state).
+            var order = new NO { OrderId = 7 };
+            var legs = new[] { new NO.LegsData { LegSymbol = 99, LegRatio = 1 } };
+            var buffer = Encode(order, legs, "PERSISTED-COID");
+
+            Assert.True(NO.TryParse(buffer, out var reader));
+
+            int legsViaForeach = 0;
+            foreach (ref readonly var _ in reader.Legs) legsViaForeach++;
+
+            int legsViaReadGroups = 0;
+            string? receivedCoid = null;
+            reader.ReadGroups(
+                (in NO.LegsData _) => legsViaReadGroups++,
+                clientOrderId =>
+                {
+                    receivedCoid = Encoding.UTF8.GetString(clientOrderId.VarData);
+                });
+
+            Assert.Equal(1, legsViaForeach);
+            Assert.Equal(1, legsViaReadGroups);
+            Assert.Equal("PERSISTED-COID", receivedCoid);
+        }
+
+        [Fact]
+        public void Foreach_EmptyGroup_WithVarDataStillReadable()
+        {
+            var order = new NO { OrderId = 1 };
+            var buffer = Encode(order, Array.Empty<NO.LegsData>(), "EMPTY-LEGS-OK");
+
+            Assert.True(NO.TryParse(buffer, out var reader));
+
+            int count = 0;
+            foreach (ref readonly var _ in reader.Legs) count++;
+            Assert.Equal(0, count);
+
+            string? coid = null;
+            reader.ReadGroups(
+                (in NO.LegsData _) => { },
+                cid => coid = Encoding.UTF8.GetString(cid.VarData));
+            Assert.Equal("EMPTY-LEGS-OK", coid);
+        }
+    }
+}