Index: tests/natools-s_expressions-atom_buffers-tests.adb
==================================================================
--- tests/natools-s_expressions-atom_buffers-tests.adb
+++ tests/natools-s_expressions-atom_buffers-tests.adb
@@ -29,10 +29,11 @@
       Test_Preallocate (Report);
       Test_Query (Report);
       Test_Query_Null (Report);
       Test_Reset (Report);
       Test_Reverse_Append (Report);
+      Test_Invert (Report);
    end All_Tests;
 
 
 
    ----------------------
@@ -60,10 +61,44 @@
       end;
    exception
       when Error : others => Report.Report_Exception (Name, Error);
    end Test_Block_Append;
 
+
+   procedure Test_Invert (Report : in out NT.Reporter'Class) is
+      Test : NT.Test := Report.Item ("Invert procedure");
+      Source : Atom (1 .. 10);
+      Inverse : Atom (1 .. 10);
+   begin
+      for I in Source'Range loop
+         Source (I) := 10 + Octet (I);
+         Inverse (11 - I) := Source (I);
+      end loop;
+
+      declare
+         Buffer : Atom_Buffer;
+      begin
+         Buffer.Invert;
+         Test_Tools.Test_Atom (Test, Null_Atom, Buffer.Data);
+
+         Buffer.Append (Source (1 .. 1));
+         Buffer.Invert;
+         Test_Tools.Test_Atom (Test, Source (1 .. 1), Buffer.Data);
+
+         Buffer.Append (Source (2 .. 7));
+         Buffer.Invert;
+         Test_Tools.Test_Atom (Test, Inverse (4 .. 10), Buffer.Data);
+
+         Buffer.Invert;
+         Buffer.Append (Source (8 .. 10));
+         Buffer.Invert;
+         Test_Tools.Test_Atom (Test, Inverse, Buffer.Data);
+      end;
+   exception
+      when Error : others => Test.Report_Exception (Error);
+   end Test_Invert;
+
 
    procedure Test_Octet_Append (Report : in out NT.Reporter'Class) is
       Name : constant String := "Append octet by octet";
       Data : Atom (0 .. 255);
    begin

Index: tests/natools-s_expressions-atom_buffers-tests.ads
==================================================================
--- tests/natools-s_expressions-atom_buffers-tests.ads
+++ tests/natools-s_expressions-atom_buffers-tests.ads
@@ -28,12 +28,13 @@
 
    procedure All_Tests (Report : in out NT.Reporter'Class);
 
    procedure Test_Block_Append (Report : in out NT.Reporter'Class);
    procedure Test_Octet_Append (Report : in out NT.Reporter'Class);
+   procedure Test_Invert (Report : in out NT.Reporter'Class);
    procedure Test_Preallocate (Report : in out NT.Reporter'Class);
    procedure Test_Query (Report : in out NT.Reporter'Class);
    procedure Test_Query_Null (Report : in out NT.Reporter'Class);
    procedure Test_Reset (Report : in out NT.Reporter'Class);
    procedure Test_Reverse_Append (Report : in out NT.Reporter'Class);
 
 end Natools.S_Expressions.Atom_Buffers.Tests;