Index: src/natools-smaz_generic.ads
==================================================================
--- src/natools-smaz_generic.ads
+++ src/natools-smaz_generic.ads
@@ -113,10 +113,23 @@
      return Positive
      is (1 + Code_Last (Dict.Offsets, Code, Dict.Values'Last)
            - Code_First (Dict.Offsets, Code, Dict.Values'First))
      with Pre => Is_Valid_Code (Dict, Code);
       --  Return the length of the string for at the given Index in Dict
+
+   function Is_Valid (Dictionary : in Smaz_Generic.Dictionary) return Boolean
+     is ((for all Code in Dictionary.Offsets'Range
+            => Dictionary.Offsets (Code) in Dictionary.Values'Range)
+        and then (for all Code in Dictionary_Code'First .. Dictionary.Last_Code
+            => Code_Last (Dictionary.Offsets, Code, Dictionary.Values'Last) + 1
+               - Code_First (Dictionary.Offsets, Code, Dictionary.Values'First)
+               in 1 .. Dictionary.Max_Word_Length)
+        and then (for all Code in Dictionary_Code'First .. Dictionary.Last_Code
+            => Dictionary_Code'Val (Dictionary.Hash
+                                      (Dict_Entry (Dictionary, Code)))
+               = Code));
+      --  Check all the assumptions made on Dictionary objects.
 
 
    function Compressed_Upper_Bound
      (Dict : in Dictionary;
       Input : in String)