Add test for collection aggregate mapping issue

tests/AutoMapper.Extensions.ExpressionMapping.UnitTests/MappingCollectionAggregateTests.cs

@@ -0,0 +1,65 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Linq.Expressions;
+using AutoMapper.Execution;
+using AutoMapper.Internal;
+using Xunit;
+
+namespace AutoMapper.Extensions.ExpressionMapping.UnitTests;
+
+public class MappingCollectionAggregateTests : AutoMapperSpecBase
+{
+    private IQueryable<Source> _sources;
+
+    public class Source
+    {
+        public ICollection<Item> Items { get; set; } = new List<Item> { new Item { Timestamp = DateTime.Now } };
+    }
+
+    public class Item
+    {
+        public DateTime Timestamp { get; set; }
+    }
+
+    public class Dest
+    {
+        public DateTime? ItemsTimestampMax { get; set; }
+    }
+
+    protected override MapperConfiguration Configuration { get; } = new MapperConfiguration(cfg =>
+    {
+        cfg.CreateMap<Source, Dest>()
+            .ForMember(dst => dst.ItemsTimestampMax, opt => opt.MapFrom(src => src.Items.Max(x => x.Timestamp)));
+
+        cfg.Internal().ForAllPropertyMaps(
+            p => p.SourceType == typeof(DateTimeOffset) && p.DestinationType == typeof(DateTimeOffset?) &&
+                p.CustomMapExpression != null, (pMap, _) =>
+            {
+                var resolver = new ExpressionResolver(Expression.Lambda(
+                    Expression.Convert(pMap.CustomMapExpression.Body, typeof(DateTimeOffset?)),
+                    pMap.CustomMapExpression.Parameters));
+
+                pMap.SetResolver(resolver);
+            });
+    });
+
+    protected override void Because_of()
+    {
+        _sources = new[] { new Source() }.AsQueryable();
+    }
+
+    [Fact]
+    public void Maps_Date_Filter()
+    {
+        _sources.UseAsDataSource(Configuration).For<Dest>()
+            .Where(d => d.ItemsTimestampMax > DateTime.Today).ToList();
+    }
+
+    [Fact]
+    public void Maps_Date_Value_Filter()
+    {
+        _sources.UseAsDataSource(Configuration).For<Dest>()
+            .Where(d => d.ItemsTimestampMax.Value.Date == DateTime.Today).ToList();
+    }
+}