Add HMAC regression tests for Decimal key parsing

Verify that HMAC produces identical digests for equivalent keys
supplied as Latin1 ('AA'), space-delimited Decimal ('65 65') and
comma-delimited Decimal ('65,65'), covering the fromDecimal Auto
delimiter behaviour originally reported in #2139 and #2217.

tests/operations/tests/Hash.mjs

@@ -722,6 +722,39 @@ TestRegister.addTests([
             }
         ]
     },
+    {
+        name: "HMAC: Decimal key space-delimited matches Latin1 key (fromDecimal Auto delimiter regression)",
+        input: "Hello, World!",
+        expectedOutput: "9b641a008211bb0464a10899d5b37a24ab08ffcf839f5e74d17d99f856530957",
+        recipeConfig: [
+            {
+                "op": "HMAC",
+                "args": [{"option": "Decimal", "string": "65 65"}, "SHA256"]
+            }
+        ]
+    },
+    {
+        name: "HMAC: Latin1 key matches space-delimited Decimal key (fromDecimal Auto delimiter regression)",
+        input: "Hello, World!",
+        expectedOutput: "9b641a008211bb0464a10899d5b37a24ab08ffcf839f5e74d17d99f856530957",
+        recipeConfig: [
+            {
+                "op": "HMAC",
+                "args": [{"option": "Latin1", "string": "AA"}, "SHA256"]
+            }
+        ]
+    },
+    {
+        name: "HMAC: Decimal key comma-delimited matches Latin1 key (fromDecimal Auto delimiter regression)",
+        input: "Hello, World!",
+        expectedOutput: "9b641a008211bb0464a10899d5b37a24ab08ffcf839f5e74d17d99f856530957",
+        recipeConfig: [
+            {
+                "op": "HMAC",
+                "args": [{"option": "Decimal", "string": "65,65"}, "SHA256"]
+            }
+        ]
+    },
     {
         name: "MD5: Complex bytes",
         input: "10dc10e32010de10d010dc10d810d910d010e12e",