The sql_variant migration is completed across the remaining inner-type-substitution sites: DATABASEPROPERTYEX, OBJECTPROPERTYEX, sys.sequences and sys.identity_columns value columns wrapping their declared types, sys.partition_range_values.value, the security-view thumbprint/algid columns, and sys.parameters.default_value.

Author: RyanLamansky

SqlServerSimulator.Tests/CollationMetadataTests.cs

@@ -221,15 +221,43 @@ public void DatabasePropertyEx_Version_ReturnsZeroAsInt()
             "SELECT DATABASEPROPERTYEX('simulated', 'Version')"));
 
     [TestMethod]
-    public void DatabasePropertyEx_Version_SurfacesAsIntType()
+    public void DatabasePropertyEx_Version_SurfacesAsSqlVariant()
     {
+        // Like real SQL Server, DATABASEPROPERTYEX projects sql_variant; the
+        // Version cell carries an int inner base type, which SqlClient unwraps.
         using var reader = new Simulation().ExecuteReader(
             "SELECT DATABASEPROPERTYEX('simulated', 'Version')");
         IsTrue(reader.Read());
-        AreEqual("int", reader.GetDataTypeName(0));
+        AreEqual("sql_variant", reader.GetDataTypeName(0));
         _ = Assert.IsInstanceOfType<int>(reader.GetValue(0));
     }
 
+    [TestMethod]
+    public void DatabasePropertyEx_Version_InnerBaseTypeIsInt()
+        => AreEqual("int", new Simulation().ExecuteScalar(
+            "SELECT SQL_VARIANT_PROPERTY(DATABASEPROPERTYEX('simulated', 'Version'), 'BaseType')"));
+
+    [TestMethod]
+    public void DatabasePropertyEx_SqlSortOrder_InnerBaseTypeIsTinyInt()
+        => AreEqual("tinyint", new Simulation().ExecuteScalar(
+            "SELECT SQL_VARIANT_PROPERTY(DATABASEPROPERTYEX('simulated', 'SQLSortOrder'), 'BaseType')"));
+
+    [TestMethod]
+    public void DatabasePropertyEx_Collation_InnerBaseTypeIsNVarchar()
+        => AreEqual("nvarchar", new Simulation().ExecuteScalar(
+            "SELECT SQL_VARIANT_PROPERTY(DATABASEPROPERTYEX('simulated', 'Collation'), 'BaseType')"));
+
+    /// <summary>
+    /// DBCC CHECKDB isn't modeled, so the property is a NULL sql_variant;
+    /// SMO's CAST(ISNULL(prop, 0) AS datetime) must resolve to 1900-01-01
+    /// (ISNULL fixes to sql_variant wrapping the int 0, CAST to datetime
+    /// epoch) — probe-confirmed against SQL Server 2025.
+    /// </summary>
+    [TestMethod]
+    public void DatabasePropertyEx_LastGoodCheckDbTime_SmoIsNullCastShape_ResolvesToEpoch()
+        => AreEqual(new DateTime(1900, 1, 1), new Simulation().ExecuteScalar(
+            "SELECT CAST(ISNULL(DATABASEPROPERTYEX('simulated', 'LastGoodCheckDbTime'), 0) AS datetime)"));
+
     [TestMethod]
     public void DatabasePropertyEx_ComparisonStyle_ReturnsInt()
         => AreEqual(196609, new Simulation().ExecuteScalar(
@@ -246,10 +274,13 @@ public void DatabasePropertyEx_SqlSortOrder_ReturnsByte52OnDefaultCollation()
             "SELECT DATABASEPROPERTYEX('simulated', 'SQLSortOrder')"));
 
     [TestMethod]
-    public void DatabasePropertyEx_NonConstantProperty_FallsBackToNVarchar()
+    public void DatabasePropertyEx_NonConstantProperty_StillProjectsSqlVariant()
     {
+        // The projection type is always sql_variant (no compile-time-constant
+        // dependency), so a non-constant property name resolves its inner base
+        // type at runtime identically — Version's int inner unwraps to 0.
         var sim = new Simulation();
-        AreEqual("0", sim.ExecuteScalar(
+        AreEqual(0, sim.ExecuteScalar(
             "declare @p nvarchar(30) = 'Version'; SELECT DATABASEPROPERTYEX('simulated', @p)"));
     }
 

SqlServerSimulator.Tests/PropertyFunctionsTests.cs

@@ -318,9 +318,13 @@ public void TypeProperty_CaseInsensitiveProperty()
 
     // === OBJECTPROPERTYEX ===
 
+    /// <summary>
+    /// OBJECTPROPERTYEX projects sql_variant; the boolean Is-X properties
+    /// carry an int inner base type, which SqlClient unwraps to an int.
+    /// </summary>
     [TestMethod]
     public void ObjectPropertyEx_IsTable_OnTable_Returns1()
-        => AreEqual("1", new Simulation().ExecuteScalar(
+        => AreEqual(1, new Simulation().ExecuteScalar(
             "create table t (id int); " +
             "select objectpropertyex(object_id('t'), 'IsTable')"));
 
@@ -346,88 +350,128 @@ public void ObjectPropertyEx_BaseType_Procedure_Returns_P()
         AreEqual("P ", sim.ExecuteScalar("select objectpropertyex(object_id('p'), 'BaseType')"));
     }
 
+    /// <summary>
+    /// SchemaId's inner base type is int.
+    /// </summary>
     [TestMethod]
     public void ObjectPropertyEx_SchemaId_Dbo_Returns1()
-        => AreEqual("1", new Simulation().ExecuteScalar(
+        => AreEqual(1, new Simulation().ExecuteScalar(
             "create table t (id int); " +
             "select objectpropertyex(object_id('t'), 'SchemaId')"));
 
+    /// <summary>
+    /// Cardinality's inner base type is bigint, which unwraps to a long.
+    /// </summary>
     [TestMethod]
     public void ObjectPropertyEx_Cardinality_EmptyTable_Returns0()
-        => AreEqual("0", new Simulation().ExecuteScalar(
+        => AreEqual(0L, new Simulation().ExecuteScalar(
             "create table t (id int); " +
             "select objectpropertyex(object_id('t'), 'Cardinality')"));
 
     [TestMethod]
     public void ObjectPropertyEx_Cardinality_ThreeRows_Returns3()
-        => AreEqual("3", new Simulation().ExecuteScalar(
+        => AreEqual(3L, new Simulation().ExecuteScalar(
             "create table t (id int); " +
             "insert t values (1), (2), (3); " +
             "select objectpropertyex(object_id('t'), 'Cardinality')"));
 
     [TestMethod]
     public void ObjectPropertyEx_TableHasIdentity_WithIdentity_Returns1()
-        => AreEqual("1", new Simulation().ExecuteScalar(
+        => AreEqual(1, new Simulation().ExecuteScalar(
             "create table t (id int identity(1,1) primary key); " +
             "select objectpropertyex(object_id('t'), 'TableHasIdentity')"));
 
     [TestMethod]
     public void ObjectPropertyEx_TableHasIdentity_NoIdentity_Returns0()
-        => AreEqual("0", new Simulation().ExecuteScalar(
+        => AreEqual(0, new Simulation().ExecuteScalar(
             "create table t (id int); " +
             "select objectpropertyex(object_id('t'), 'TableHasIdentity')"));
 
     [TestMethod]
     public void ObjectPropertyEx_TableHasPrimaryKey_WithPK_Returns1()
-        => AreEqual("1", new Simulation().ExecuteScalar(
+        => AreEqual(1, new Simulation().ExecuteScalar(
             "create table t (id int primary key); " +
             "select objectpropertyex(object_id('t'), 'TableHasPrimaryKey')"));
 
     [TestMethod]
     public void ObjectPropertyEx_TableHasPrimaryKey_NoPK_Returns0()
-        => AreEqual("0", new Simulation().ExecuteScalar(
+        => AreEqual(0, new Simulation().ExecuteScalar(
             "create table t (id int); " +
             "select objectpropertyex(object_id('t'), 'TableHasPrimaryKey')"));
 
     [TestMethod]
     public void ObjectPropertyEx_TableHasUniqueCnst_WithUnique_Returns1()
-        => AreEqual("1", new Simulation().ExecuteScalar(
+        => AreEqual(1, new Simulation().ExecuteScalar(
             "create table t (id int, name varchar(50), constraint uq unique (name)); " +
             "select objectpropertyex(object_id('t'), 'TableHasUniqueCnst')"));
 
     [TestMethod]
     public void ObjectPropertyEx_TableHasCheckCnst_WithCheck_Returns1()
-        => AreEqual("1", new Simulation().ExecuteScalar(
+        => AreEqual(1, new Simulation().ExecuteScalar(
             "create table t (id int, check (id > 0)); " +
             "select objectpropertyex(object_id('t'), 'TableHasCheckCnst')"));
 
     [TestMethod]
     public void ObjectPropertyEx_TableHasForeignKey_WithFK_Returns1()
-        => AreEqual("1", new Simulation().ExecuteScalar(
+        => AreEqual(1, new Simulation().ExecuteScalar(
             "create table p (id int primary key); " +
             "create table c (id int primary key, p_id int references p(id)); " +
             "select objectpropertyex(object_id('c'), 'TableHasForeignKey')"));
 
     [TestMethod]
     public void ObjectPropertyEx_TableHasForeignRef_WithIncoming_Returns1()
-        => AreEqual("1", new Simulation().ExecuteScalar(
+        => AreEqual(1, new Simulation().ExecuteScalar(
             "create table p (id int primary key); " +
             "create table c (id int primary key, p_id int references p(id)); " +
             "select objectpropertyex(object_id('p'), 'TableHasForeignRef')"));
 
     [TestMethod]
     public void ObjectPropertyEx_TableHasIndex_WithIndex_Returns1()
-        => AreEqual("1", new Simulation().ExecuteScalar(
+        => AreEqual(1, new Simulation().ExecuteScalar(
             "create table t (id int, name varchar(50)); " +
             "create index ix on t(name); " +
             "select objectpropertyex(object_id('t'), 'TableHasIndex')"));
 
     [TestMethod]
     public void ObjectPropertyEx_TableHasRowGuidCol_AlwaysZero()
-        => AreEqual("0", new Simulation().ExecuteScalar(
+        => AreEqual(0, new Simulation().ExecuteScalar(
             "create table t (id int); " +
             "select objectpropertyex(object_id('t'), 'TableHasRowGuidCol')"));
 
+    [TestMethod]
+    public void ObjectPropertyEx_ProjectsSqlVariant()
+    {
+        using var reader = new Simulation().ExecuteReader(
+            "create table t (id int); " +
+            "select objectpropertyex(object_id('t'), 'SchemaId')");
+        IsTrue(reader.Read());
+        AreEqual("sql_variant", reader.GetDataTypeName(0));
+    }
+
+    [TestMethod]
+    public void ObjectPropertyEx_BaseType_InnerBaseTypeIsChar()
+        => AreEqual("char", new Simulation().ExecuteScalar(
+            "create table t (id int); " +
+            "select sql_variant_property(objectpropertyex(object_id('t'), 'BaseType'), 'BaseType')"));
+
+    [TestMethod]
+    public void ObjectPropertyEx_SchemaId_InnerBaseTypeIsInt()
+        => AreEqual("int", new Simulation().ExecuteScalar(
+            "create table t (id int); " +
+            "select sql_variant_property(objectpropertyex(object_id('t'), 'SchemaId'), 'BaseType')"));
+
+    [TestMethod]
+    public void ObjectPropertyEx_Cardinality_InnerBaseTypeIsBigInt()
+        => AreEqual("bigint", new Simulation().ExecuteScalar(
+            "create table t (id int); " +
+            "select sql_variant_property(objectpropertyex(object_id('t'), 'Cardinality'), 'BaseType')"));
+
+    [TestMethod]
+    public void ObjectPropertyEx_TableHasIdentity_InnerBaseTypeIsInt()
+        => AreEqual("int", new Simulation().ExecuteScalar(
+            "create table t (id int identity(1,1)); " +
+            "select sql_variant_property(objectpropertyex(object_id('t'), 'TableHasIdentity'), 'BaseType')"));
+
     [TestMethod]
     public void ObjectPropertyEx_UnknownProperty_ReturnsNull()
         => AreEqual(DBNull.Value, new Simulation().ExecuteScalar(

SqlServerSimulator.Tests/SequenceTests.cs

@@ -331,11 +331,15 @@ public void SysSequences_ListsRegisteredSequences()
             """).ExecuteReader();
         IsTrue(reader.Read());
         AreEqual("sysview1", reader.GetString(0));
-        AreEqual(100L, reader.GetInt64(1));
-        AreEqual(5L, reader.GetInt64(2));
+        // start_value / increment / current_value are sql_variant carrying the
+        // sequence's declared type (int here); SqlClient surfaces the inner int
+        // via GetValue.
+        AreEqual("sql_variant", reader.GetDataTypeName(1));
+        AreEqual(100, reader.GetValue(1));
+        AreEqual(5, reader.GetValue(2));
         IsTrue(reader.GetBoolean(3));
         IsFalse(reader.GetBoolean(4));
-        AreEqual(100L, reader.GetInt64(5));
+        AreEqual(100, reader.GetValue(5));
     }
 
     [TestMethod]
@@ -346,9 +350,31 @@ public void SysSequences_AfterAdvance_CurrentValueUpdates()
         _ = simulation.ExecuteScalar("select next value for sysview2");
         _ = simulation.ExecuteScalar("select next value for sysview2");
         // After two advances starting from 1 with increment 1, current_value
-        // is the next value to emit: 3.
-        AreEqual(3L, simulation.ExecuteScalar<long>("select current_value from sys.sequences where name = 'sysview2'"));
-    }
+        // is the next value to emit: 3 (int inner base type for an int sequence).
+        AreEqual(3, simulation.ExecuteScalar<int>("select current_value from sys.sequences where name = 'sysview2'"));
+    }
+
+    // A decimal sequence's inner type reports BaseType 'numeric' — the
+    // simulator's single decimal family surfaces as numeric (documented quirk),
+    // diverging from real's 'decimal' for a decimal-declared sequence.
+    [TestMethod]
+    [DataRow("bigint", "bigint")]
+    [DataRow("int", "int")]
+    [DataRow("smallint", "smallint")]
+    [DataRow("tinyint", "tinyint")]
+    [DataRow("decimal(18,0)", "numeric")]
+    public void SysSequences_StartValue_InnerBaseTypeMatchesDeclaredType(string declared, string expectedBaseType)
+        => AreEqual(expectedBaseType, new Simulation().ExecuteScalar($"""
+            create sequence sv_bt as {declared} start with 5;
+            select sql_variant_property(start_value, 'BaseType') from sys.sequences where name = 'sv_bt'
+            """));
+
+    [TestMethod]
+    public void SysSequences_BigIntSequence_StartValueUnwrapsToLong()
+        => AreEqual(5000000000L, new Simulation().ExecuteScalar("""
+            create sequence sv_big as bigint start with 5000000000;
+            select start_value from sys.sequences where name = 'sv_big'
+            """));
 
     /// <summary>
     /// last_used_value is NULL until the first NEXT VALUE FOR (probe-confirmed:

SqlServerSimulator.Tests/SsmsScriptTableCatalogTests.cs

@@ -81,8 +81,11 @@ public void IdentityColumns_ProjectsSeedAndIncrement()
             "select name, seed_value, increment_value, cast(is_not_for_replication as int) from sys.identity_columns where object_id = object_id('t')");
         IsTrue(reader.Read());
         AreEqual("id", reader.GetString(0));
-        AreEqual(5L, reader.GetInt64(1));
-        AreEqual(3L, reader.GetInt64(2));
+        // seed_value / increment_value are sql_variant carrying the identity
+        // column's declared type (int here); SqlClient surfaces the inner int.
+        AreEqual("sql_variant", reader.GetDataTypeName(1));
+        AreEqual(5, reader.GetValue(1));
+        AreEqual(3, reader.GetValue(2));
         AreEqual(0, reader.GetInt32(3));
         IsFalse(reader.Read());
     }
@@ -94,6 +97,27 @@ public void IdentityColumns_LastValueNullBeforeFirstInsert()
             select case when last_value is null then 1 else 0 end from sys.identity_columns where object_id = object_id('t')
             """));
 
+    // Decimal identity columns aren't modeled (Msg 2749), so only the integer
+    // family is exercised here.
+    [TestMethod]
+    [DataRow("bigint", "bigint")]
+    [DataRow("int", "int")]
+    [DataRow("smallint", "smallint")]
+    [DataRow("tinyint", "tinyint")]
+    public void IdentityColumns_SeedValue_InnerBaseTypeMatchesColumnType(string declared, string expectedBaseType)
+        => AreEqual(expectedBaseType, new Simulation().ExecuteScalar($"""
+            create table t (id {declared} identity(5, 3) not null primary key);
+            select sql_variant_property(seed_value, 'BaseType') from sys.identity_columns where object_id = object_id('t')
+            """));
+
+    [TestMethod]
+    public void IdentityColumns_LastValue_InnerBaseTypeIsColumnType_AfterInsert()
+        => AreEqual("bigint", new Simulation().ExecuteScalar("""
+            create table t (id bigint identity(1, 1) not null primary key, x int);
+            insert t (x) values (1);
+            select sql_variant_property(last_value, 'BaseType') from sys.identity_columns where object_id = object_id('t')
+            """));
+
     // === sys.trigger_events ===
 
     [TestMethod]