Index: tests/natools-string_slice_set_tests.adb
==================================================================
--- tests/natools-string_slice_set_tests.adb
+++ tests/natools-string_slice_set_tests.adb
@@ -106,10 +106,11 @@
    begin
       Test_Conversions (Report);
       Test_Exceptions (Report);
       Test_Interval_Arithmetic (Report);
       Test_Navigation (Report);
+      Test_Slices (Report);
       Test_Tokenization (Report);
    end All_Tests;
 
 
 
@@ -870,10 +871,43 @@
       Report.Item (Name, NT.Success);
    exception
       when Error : others => Report.Report_Exception (Name, Error);
    end Test_Navigation;
 
+
+   procedure Test_Slices (Report : in out NT.Reporter'Class) is
+      Name : constant String := "Slice-based operations";
+      Parent : constant String_Slices.Slice
+        := String_Slices.To_Slice (Parent_String);
+      Unrelated : constant String_Slices.Slice
+        := String_Slices.To_Slice (Name);
+      Set_1, Set_2, Set_3 : Slice_Sets.Slice_Set;
+
+      use type Slice_Sets.Slice_Set;
+   begin
+      Set_1.Include_Slice (Unrelated.Subslice (10, 9));
+      Set_1.Add_Slice (Parent);
+      Set_2.Add_Slice (Parent.Subslice (20, 29));
+      Set_2.Add_Slice (Unrelated.Subslice (25, 24));
+      Set_2.Include_Slice (Parent);
+      Set_3.Include_Slice (Parent.Subslice (20, 29));
+      Set_3.Add_Slice (Parent.Subslice (35, 39));
+      Set_3.Include_Slice (Parent);
+
+      if Set_1 = Set_2 and Set_1 = Set_3 then
+         Report.Item (Name, NT.Success);
+      else
+         Report.Item (Name, NT.Fail);
+         Report.Info ("Add_Slice and Include_Slice not equivalent");
+         Dump (Report, Set_1);
+         Dump (Report, Set_2);
+         Dump (Report, Set_3);
+      end if;
+   exception
+      when Error : others => Report.Report_Exception (Name, Error);
+   end Test_Slices;
+
 
    procedure Test_Tokenization (Report : in out NT.Reporter'Class) is
       Name : constant String := "Simple tokenization";
       Space : constant Ada.Strings.Maps.Character_Set
         := Ada.Strings.Maps.To_Set (" ");

Index: tests/natools-string_slice_set_tests.ads
==================================================================
--- tests/natools-string_slice_set_tests.ads
+++ tests/natools-string_slice_set_tests.ads
@@ -30,8 +30,9 @@
 
    procedure Test_Conversions (Report : in out NT.Reporter'Class);
    procedure Test_Exceptions (Report : in out NT.Reporter'Class);
    procedure Test_Interval_Arithmetic (Report : in out NT.Reporter'Class);
    procedure Test_Navigation (Report : in out NT.Reporter'Class);
+   procedure Test_Slices (Report : in out NT.Reporter'Class);
    procedure Test_Tokenization (Report : in out NT.Reporter'Class);
 
 end Natools.String_Slice_Set_Tests;