diff --git a/tests/test_serializer_xkb.py b/tests/test_serializer_xkb.py
index 45319db..febf4f5 100644
--- a/tests/test_serializer_xkb.py
+++ b/tests/test_serializer_xkb.py
@@ -1,4 +1,5 @@
 from textwrap import dedent
+from typing import Dict
 
 from kalamine import KeyboardLayout
 from kalamine.generators.xkb import xkb_table
@@ -6,8 +7,10 @@
 from .util import get_layout_dict
 
 
-def load_layout(filename: str) -> KeyboardLayout:
-    return KeyboardLayout(get_layout_dict(filename))
+def load_layout(
+    filename: str, extraMapping: Dict[str, Dict[str, str]]
+) -> KeyboardLayout:
+    return KeyboardLayout(get_layout_dict(filename, extraMapping))
 
 
 def split(multiline_str: str):
@@ -15,7 +18,7 @@ def split(multiline_str: str):
 
 
 def test_ansi():
-    layout = load_layout("ansi")
+    layout = load_layout("ansi", {})
 
     expected = split(
         """
@@ -91,8 +94,6 @@ def test_ansi():
 
 
 def test_intl():
-    layout = load_layout("intl")
-
     expected = split(
         """
         // Digits
@@ -158,17 +159,46 @@ def test_intl():
         """
     )
 
-    xkbcomp = xkb_table(layout, xkbcomp=True)
-    assert len(xkbcomp) == len(expected)
-    assert xkbcomp == expected
+    extraMapping = {
+        # NOTE: redefine level
+        "ae01": {"shift": "?"},
+        # NOTE: test case variants and ODK alias
+        "menu": {"base": "a", "sHiFt": "A", "1dk": "æ", "ODk_shiFt": "Æ"},
+        # NOTE: clone level
+        "esc": {"base": "(ae11)"},
+        # NOTE: clone key
+        "i172": "(lsgt)",
+    }
+
+    extraSymbols = [
+        "",
+        "// System",
+        "key <ESC>  {[ minus           , VoidSymbol      , VoidSymbol      , VoidSymbol      ]}; // -",
+        "key <MENU> {[ a               , A               , ae              , AE              ]}; // a A æ Æ",
+        "",
+        "// Miscellaneous",
+        "key <I172> {[ backslash       , bar             , VoidSymbol      , VoidSymbol      ]}; // \\ |",
+    ]
+
+    extraExpected = expected + extraSymbols
+    extraExpected[1] = (
+        "key <AE01> {[ 1               , question        , VoidSymbol      , VoidSymbol      ]}; // 1 ?"
+    )
 
-    xkbpatch = xkb_table(layout, xkbcomp=False)
-    assert len(xkbpatch) == len(expected)
-    assert xkbpatch == expected
+    for mapping, expectedʹ in (({}, expected), (extraMapping, extraExpected)):
+        layout = load_layout("intl", mapping)
+
+        xkbcomp = xkb_table(layout, xkbcomp=True)
+        assert len(xkbcomp) == len(expectedʹ)
+        assert xkbcomp == expectedʹ
+
+        xkbpatch = xkb_table(layout, xkbcomp=False)
+        assert len(xkbpatch) == len(expectedʹ)
+        assert xkbpatch == expectedʹ
 
 
 def test_prog():
-    layout = load_layout("prog")
+    layout = load_layout("prog", {})
 
     expected = split(
         """
diff --git a/tests/util.py b/tests/util.py
index c4b35f2..45a8d0b 100644
--- a/tests/util.py
+++ b/tests/util.py
@@ -1,14 +1,19 @@
 """Some util functions for tests."""
 
 from pathlib import Path
-from typing import Dict
+from typing import Dict, Optional
 
 import tomli
 
 
-def get_layout_dict(filename: str) -> Dict:
+def get_layout_dict(
+    filename: str, extraMapping: Optional[Dict[str, Dict[str, str]]] = None
+) -> Dict:
     """Return the layout directory path."""
 
     file_path = Path(__file__).parent.parent / f"layouts/{filename}.toml"
     with file_path.open(mode="rb") as file:
-        return tomli.load(file)
+        layout = tomli.load(file)
+        if extraMapping:
+            layout.update({"mapping": extraMapping})
+        return layout