Index: tests/natools-s_expressions-parsers-tests.adb
==================================================================
--- tests/natools-s_expressions-parsers-tests.adb
+++ tests/natools-s_expressions-parsers-tests.adb
@@ -12,10 +12,11 @@
 -- WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN    --
 -- ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF  --
 -- OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.           --
 ------------------------------------------------------------------------------
 
+with Natools.S_Expressions.Lockable.Tests;
 with Natools.S_Expressions.Printers;
 with Natools.S_Expressions.Test_Tools;
 
 package body Natools.S_Expressions.Parsers.Tests is
 
@@ -121,10 +122,11 @@
       Nested_Subpexression (Report);
       Number_Prefixes (Report);
       Quoted_Escapes (Report);
       Parser_Interface (Report);
       Subparser_Interface (Report);
+      Lockable_Interface (Report);
    end All_Tests;
 
 
 
    -----------------------
@@ -169,10 +171,27 @@
          Expected => To_Atom ("4:head((7:sublist)5:token)4:tail"));
    begin
       Test (Report);
    end Base64_Subexpression;
 
+
+   procedure Lockable_Interface (Report : in out NT.Reporter'Class) is
+      Test : NT.Test := Report.Item ("Lockable.Descriptor interface");
+   begin
+      declare
+         Input : aliased Test_Tools.Memory_Stream;
+         Parser : aliased Parsers.Parser;
+         Sub : Subparser (Parser'Access, Input'Access);
+      begin
+         Input.Set_Data (Lockable.Tests.Test_Expression);
+         Test_Tools.Next_And_Check (Test, Sub, Events.Open_List, 1);
+         Lockable.Tests.Test_Interface (Test, Sub);
+      end;
+   exception
+      when Error : others => Test.Report_Exception (Error);
+   end Lockable_Interface;
+
 
    procedure Nested_Subpexression (Report : in out NT.Reporter'Class) is
       procedure Test is new Blackbox_Test
         (Name => "Nested base-64 subepxressions",
          Source => To_Atom ("(5:begin"
@@ -441,14 +460,14 @@
          pragma Assert (Parser.Current_Event = Events.Add_Atom
            and then Parser.Current_Atom = To_Atom ("command"));
 
          --  Use subparser as command arguments
 
-         Test_Tools.Next_And_Check (Test, Sub, To_Atom ("arg1"), 2);
-         Test_Tools.Next_And_Check (Test, Sub, Events.Open_List, 3);
-         Test_Tools.Next_And_Check (Test, Sub, To_Atom ("subarg1"), 3);
-         Test_Tools.Next_And_Check (Test, Sub, To_Atom ("subarg2"), 3);
+         Test_Tools.Next_And_Check (Test, Sub, To_Atom ("arg1"), 0);
+         Test_Tools.Next_And_Check (Test, Sub, Events.Open_List, 1);
+         Test_Tools.Next_And_Check (Test, Sub, To_Atom ("subarg1"), 1);
+         Test_Tools.Next_And_Check (Test, Sub, To_Atom ("subarg2"), 1);
 
          Sub.Finish;
 
          --  Check final state of parser
 
@@ -477,16 +496,16 @@
 
          --  Check subparser error states
 
          if Sub.Current_Event /= Events.End_Of_Input then
             Test.Fail ("Unexpected subparser final state: "
-              & Events.Event'Image (Parser.Current_Event));
+              & Events.Event'Image (Sub.Current_Event));
          end if;
 
-         if Sub.Current_Level /= 2 then
+         if Sub.Current_Level /= 0 then
             Test.Fail ("Unexpected subparser final level:"
-              & Natural'Image (Parser.Current_Level));
+              & Natural'Image (Sub.Current_Level));
          end if;
 
          begin
             declare
                Buffer : constant Atom := Sub.Current_Atom;
@@ -495,11 +514,11 @@
                  ("No exception raised in Current_Atom on finished subparser");
                Test_Tools.Dump_Atom (Test, Buffer);
             end;
             return;
          exception
-            when Constraint_Error => null;
+            when Program_Error => null;
             when Error : others =>
                Test.Report_Exception (Error);
                Test.Info ("in Current_Atom");
          end;
 
@@ -511,11 +530,11 @@
             Test.Fail
               ("No exception raised in Read_Atom on finished subparser");
             Test_Tools.Dump_Atom (Test, Buffer (1 .. Length));
             return;
          exception
-            when Constraint_Error => null;
+            when Program_Error => null;
             when Error : others =>
                Test.Report_Exception (Error);
                Test.Info ("in Read_Atom");
                Test_Tools.Dump_Atom (Test, Buffer (1 .. Length), "Buffer");
                return;
@@ -539,11 +558,11 @@
             if Called then
                Test_Tools.Dump_Atom (Test, Output.Get_Data,
                  "Process called with");
             end if;
          exception
-            when Constraint_Error => null;
+            when Program_Error => null;
             when Error : others =>
                Test.Report_Exception (Error);
                Test.Info ("in Query_Event");
                if Called then
                   Test_Tools.Dump_Atom (Test, Output.Get_Data,

Index: tests/natools-s_expressions-parsers-tests.ads
==================================================================
--- tests/natools-s_expressions-parsers-tests.ads
+++ tests/natools-s_expressions-parsers-tests.ads
@@ -29,13 +29,14 @@
    procedure All_Tests (Report : in out NT.Reporter'Class);
 
    procedure Atom_Encodings (Report : in out NT.Reporter'Class);
    procedure Base64_Subexpression (Report : in out NT.Reporter'Class);
    procedure Canonical_Encoding (Report : in out NT.Reporter'Class);
+   procedure Lockable_Interface (Report : in out NT.Reporter'Class);
    procedure Nested_Subpexression (Report : in out NT.Reporter'Class);
    procedure Number_Prefixes (Report : in out NT.Reporter'Class);
    procedure Parser_Interface (Report : in out NT.Reporter'Class);
    procedure Quoted_Escapes (Report : in out NT.Reporter'Class);
    procedure Special_Subexpression (Report : in out NT.Reporter'Class);
    procedure Subparser_Interface (Report : in out NT.Reporter'Class);
 
 end Natools.S_Expressions.Parsers.Tests;