Adding regression test for #15279

We already have regression tests for most of the scenarios mentioned in the issue report. Adding the one scenario that was missing.

Resolves #15279

test/EFCore.Specification.Tests/Query/NorthwindGroupByQueryTestBase.cs

@@ -3300,6 +3300,31 @@ public virtual Task Complex_query_with_groupBy_in_subquery4(bool async)
                 });
         }
 
+        [ConditionalTheory]
+        [MemberData(nameof(IsAsyncData))]
+        public virtual Task Complex_query_with_group_by_in_subquery5(bool async)
+        {
+            return AssertQuery(
+                async,
+                ss => from od in ss.Set<OrderDetail>()
+                      where od.Order.Customer.CustomerID == "ALFKI"
+                      group od by od.ProductID into grouping
+                      select new
+                      {
+                          Sum = grouping.Sum(x => x.ProductID + x.OrderID * 1000),
+                          Subquery = (from c in ss.Set<Customer>()
+                                      where c.CustomerID.Length < grouping.Min(x => x.OrderID / 100)
+                                      orderby c.CustomerID
+                                      select new { c.CustomerID, c.City }).ToList()
+                      },
+                elementSorter: e => e.Sum,
+                elementAsserter: (e, a) =>
+                {
+                    AssertEqual(e.Sum, a.Sum);
+                    AssertCollection(e.Subquery, a.Subquery, elementSorter: ee => ee.CustomerID);
+                });
+        }
+
         [ConditionalTheory]
         [MemberData(nameof(IsAsyncData))]
         public virtual Task GroupBy_scalar_subquery(bool async)

test/EFCore.SqlServer.FunctionalTests/Query/NorthwindGroupByQuerySqlServerTest.cs

@@ -2847,6 +2847,33 @@ public override async Task Select_correlated_collection_after_GroupBy_aggregate_
             //AssertSql(" ");
         }
 
+        public override async Task Complex_query_with_group_by_in_subquery5(bool async)
+        {
+            await base.Complex_query_with_group_by_in_subquery5(async);
+
+            AssertSql(
+                @"SELECT [t].[c], [t].[ProductID], [t0].[CustomerID], [t0].[City]
+FROM (
+    SELECT COALESCE(SUM([o].[ProductID] + ([o].[OrderID] * 1000)), 0) AS [c], [o].[ProductID]
+    FROM [Order Details] AS [o]
+    INNER JOIN [Orders] AS [o0] ON [o].[OrderID] = [o0].[OrderID]
+    LEFT JOIN [Customers] AS [c] ON [o0].[CustomerID] = [c].[CustomerID]
+    WHERE [c].[CustomerID] = N'ALFKI'
+    GROUP BY [o].[ProductID]
+) AS [t]
+OUTER APPLY (
+    SELECT [c0].[CustomerID], [c0].[City]
+    FROM [Customers] AS [c0]
+    WHERE CAST(LEN([c0].[CustomerID]) AS int) < (
+        SELECT MIN([o1].[OrderID] / 100)
+        FROM [Order Details] AS [o1]
+        INNER JOIN [Orders] AS [o2] ON [o1].[OrderID] = [o2].[OrderID]
+        LEFT JOIN [Customers] AS [c1] ON [o2].[CustomerID] = [c1].[CustomerID]
+        WHERE ([c1].[CustomerID] = N'ALFKI') AND ([t].[ProductID] = [o1].[ProductID]))
+) AS [t0]
+ORDER BY [t].[ProductID], [t0].[CustomerID]");
+        }
+
         private void AssertSql(params string[] expected)
             => Fixture.TestSqlLoggerFactory.AssertBaseline(expected);
 

test/EFCore.Sqlite.FunctionalTests/Query/NorthwindGroupByQuerySqliteTest.cs

@@ -68,6 +68,12 @@ public override async Task Select_nested_collection_with_groupby(bool async)
                 (await Assert.ThrowsAsync<InvalidOperationException>(
                     () => base.Select_nested_collection_with_groupby(async))).Message);
 
+        public override async Task Complex_query_with_group_by_in_subquery5(bool async)
+            => Assert.Equal(
+                SqliteStrings.ApplyNotSupported,
+                (await Assert.ThrowsAsync<InvalidOperationException>(
+                    () => base.Complex_query_with_group_by_in_subquery5(async))).Message);
+
         public override async Task Odata_groupby_empty_key(bool async)
             => await Assert.ThrowsAsync<NotSupportedException>(() => base.Odata_groupby_empty_key(async));
     }