diff --git a/test/EFCore.Specification.Tests/Query/NorthwindFunctionsQueryTestBase.cs b/test/EFCore.Specification.Tests/Query/NorthwindFunctionsQueryTestBase.cs
index 29aa6b231cb..130c86aacff 100644
--- a/test/EFCore.Specification.Tests/Query/NorthwindFunctionsQueryTestBase.cs
+++ b/test/EFCore.Specification.Tests/Query/NorthwindFunctionsQueryTestBase.cs
@@ -1858,12 +1858,12 @@ public virtual Task Where_DateOnly_FromDateTime(bool async)
     public virtual Task Select_ToString_IndexOf(bool async)
         => AssertQuery(
             async,
-            ss => ss.Set<Order>().Select(x => x.OrderID.ToString().IndexOf("123")));
+            ss => ss.Set<Order>().Where(x => x.OrderID.ToString().IndexOf("123") == -1));
 
     [ConditionalTheory]
     [MemberData(nameof(IsAsyncData))]
     public virtual Task Select_IndexOf_ToString(bool async)
         => AssertQuery(
             async,
-            ss => ss.Set<Order>().Select(x => "123".IndexOf(x.OrderID.ToString())));
+            ss => ss.Set<Order>().Where(x => "123".IndexOf(x.OrderID.ToString()) == -1));
 }
diff --git a/test/EFCore.SqlServer.FunctionalTests/Query/NorthwindFunctionsQuerySqlServerTest.cs b/test/EFCore.SqlServer.FunctionalTests/Query/NorthwindFunctionsQuerySqlServerTest.cs
index 254839d42da..640920331a4 100644
--- a/test/EFCore.SqlServer.FunctionalTests/Query/NorthwindFunctionsQuerySqlServerTest.cs
+++ b/test/EFCore.SqlServer.FunctionalTests/Query/NorthwindFunctionsQuerySqlServerTest.cs
@@ -2729,8 +2729,9 @@ public override async Task Select_ToString_IndexOf(bool async)
 
         AssertSql(
             """
-SELECT CAST(CHARINDEX(N'123', CONVERT(varchar(11), [o].[OrderID])) AS int) - 1
+SELECT [o].[OrderID], [o].[CustomerID], [o].[EmployeeID], [o].[OrderDate]
 FROM [Orders] AS [o]
+WHERE CAST(CHARINDEX(N'123', CONVERT(varchar(11), [o].[OrderID])) AS int) - 1 = -1
 """);
     }
 
@@ -2740,11 +2741,12 @@ public override async Task Select_IndexOf_ToString(bool async)
 
         AssertSql(
             """
-SELECT CASE
+SELECT [o].[OrderID], [o].[CustomerID], [o].[EmployeeID], [o].[OrderDate]
+FROM [Orders] AS [o]
+WHERE CASE
     WHEN CONVERT(varchar(11), [o].[OrderID]) = N'' THEN 0
     ELSE CAST(CHARINDEX(CONVERT(varchar(11), [o].[OrderID]), N'123') AS int) - 1
-END
-FROM [Orders] AS [o]
+END = -1
 """);
     }
 
diff --git a/test/EFCore.Sqlite.FunctionalTests/Query/NorthwindFunctionsQuerySqliteTest.cs b/test/EFCore.Sqlite.FunctionalTests/Query/NorthwindFunctionsQuerySqliteTest.cs
index 39867c717f3..826c4d1b27f 100644
--- a/test/EFCore.Sqlite.FunctionalTests/Query/NorthwindFunctionsQuerySqliteTest.cs
+++ b/test/EFCore.Sqlite.FunctionalTests/Query/NorthwindFunctionsQuerySqliteTest.cs
@@ -1486,8 +1486,9 @@ public override async Task Select_ToString_IndexOf(bool async)
 
         AssertSql(
             """
-SELECT instr(CAST("o"."OrderID" AS TEXT), '123') - 1
+SELECT "o"."OrderID", "o"."CustomerID", "o"."EmployeeID", "o"."OrderDate"
 FROM "Orders" AS "o"
+WHERE instr(CAST("o"."OrderID" AS TEXT), '123') - 1 = -1
 """);
     }
 
@@ -1497,8 +1498,9 @@ public override async Task Select_IndexOf_ToString(bool async)
 
         AssertSql(
             """
-SELECT instr('123', CAST("o"."OrderID" AS TEXT)) - 1
+SELECT "o"."OrderID", "o"."CustomerID", "o"."EmployeeID", "o"."OrderDate"
 FROM "Orders" AS "o"
+WHERE instr('123', CAST("o"."OrderID" AS TEXT)) - 1 = -1
 """);
     }