immplement Element behaviour and some tests

src/dabmodel/LAMFields/Constraint.py

@@ -0,0 +1,17 @@
+from typing import Generic, TypeVar
+
+T_Field = TypeVar("T_Field")
+
+
+class Constraint(Generic[T_Field]):
+    """Constraint class
+    Base class for Field's constraints
+    """
+
+    _bound_type: type
+
+    def __init__(self): ...
+
+    def check(self, value: T_Field) -> bool:
+        """Check if a Constraint is completed"""
+        return True

src/dabmodel/LAMFields/FrozenLAMField.py

@@ -0,0 +1,41 @@
+from typing import Generic, TypeVar, Any
+
+from .LAMField import LAMField
+from .Constraint import Constraint
+from ..tools import LAMdeepfreeze
+
+T_Field = TypeVar("T_Field")
+
+
+class FrozenLAMField(Generic[T_Field]):
+    """FrozenLAMField class
+    a read-only proxy of a Field
+    """
+
+    def __init__(self, inner_field: LAMField[T_Field]):
+        self._inner_field = inner_field
+
+    @property
+    def doc(self) -> str:
+        """Returns Field's documentation (frozen)"""
+        return LAMdeepfreeze(self._inner_field.doc)
+
+    @property
+    def constraints(self) -> tuple[Constraint]:
+        """Returns Field's constraint (frozen)"""
+        return LAMdeepfreeze(self._inner_field.constraints)
+
+    @property
+    def default_value(self) -> Any:
+        """Returns Field's default value (frozen)"""
+        return self._inner_field.default_value
+
+    @property
+    def value(self) -> Any:
+        """Returns Field's value (frosen)"""
+        return self._inner_field.value
+
+    @property
+    def annotations(self) -> Any:
+        """Returns Field's annotation (frozen)"""
+        return LAMdeepfreeze(self._inner_field.annotations)

src/dabmodel/LAMFields/LAMCompatible.py

@@ -0,0 +1,38 @@
+from typing import Generic, TypeVar, Self, Hashable, Any
+from abc import ABC, abstractmethod
+from ..tools import JSONType
+
+TV_LAMCompatbile = TypeVar("TV_LABCompatbile", bound="LABCompatible")
+
+
+class LAMCompatible(Generic[TV_LAMCompatbile], ABC):
+    """Any type that can safely live inside a LABField."""
+
+    @classmethod
+    def lam_validate_annotation(cls, annotation: Any) -> None:
+        """
+        Validate the type annotation (e.g., SpecialList[int]).
+        Raise if it's not compatible.
+        """
+        return  # default: do nothing (simple types don’t need it)
+
+    @abstractmethod
+    def lam_validate(self) -> None:
+        """Raise if the value is invalid for this type."""
+        ...
+
+    @abstractmethod
+    def lam_freeze(self) -> Hashable:
+        """Return an immutable/hashable representation of this value."""
+        ...
+
+    @abstractmethod
+    def lam_to_plain(self) -> JSONType:
+        """Return a plain serializable form (str, dict, etc.)."""
+        ...
+
+    @classmethod
+    @abstractmethod
+    def lam_from_plain(cls, plain: JSONType) -> Self:
+        """Return an Object from a plain serializable form (str, dict, etc.)."""
+        ...

src/dabmodel/LAMFields/LAMField.py

@@ -0,0 +1,62 @@
+from typing import Generic, TypeVar, Optional, Any
+
+from .LAMFieldInfo import LAMFieldInfo
+from .Constraint import Constraint
+from ..tools import LAMdeepfreeze
+
+TV_LABField = TypeVar("TV_LABField")
+
+
+class LAMField(Generic[TV_LABField]):
+    """This class describe a Field in Schema"""
+
+    def __init__(self, name: str, v: Optional[TV_LABField], a: Any, i: LAMFieldInfo):
+        self._name: str = name
+        self._source: Optional[type] = None
+        self._default_value: Optional[TV_LABField] = v
+        self._value: Optional[TV_LABField] = v
+        self._annotations: Any = a
+        self._info: LAMFieldInfo = i
+        self._constraints: list[Constraint[Any]] = i.constraints
+
+    def add_source(self, s: type) -> None:
+        """Adds source Appliance to the Field"""
+        self._source = s
+
+    @property
+    def doc(self) -> str:
+        """Returns Field's documentation"""
+        return self._info.doc
+
+    def add_constraint(self, c: Constraint) -> None:
+        """Adds constraint to the Field"""
+        self._constraints.append(c)
+
+    @property
+    def constraints(self) -> list[Constraint]:
+        """Returns Field's constraint"""
+        return self._info.constraints
+
+    @property
+    def default_value(self) -> Any:
+        """Returns Field's default value (frozen)"""
+        return LAMdeepfreeze(self._default_value)
+
+    def update_value(self, v: Optional[TV_LABField] = None) -> None:
+        """Updates Field's value"""
+        self._value = v
+
+    @property
+    def value(self) -> Any:
+        """Returns Field's value (frozen)"""
+        return LAMdeepfreeze(self._value)
+
+    @property
+    def raw_value(self) -> Optional[TV_LABField]:
+        """Returns Field's value"""
+        return self._value
+
+    @property
+    def annotations(self) -> Any:
+        """Returns Field's annotation"""
+        return self._annotations

src/dabmodel/LAMFields/LAMFieldInfo.py

@@ -0,0 +1,26 @@
+from typing import Optional, Any
+from .Constraint import Constraint
+
+
+class LAMFieldInfo:
+    """This Class allows to describe a Field in Appliance class"""
+
+    def __init__(
+        self, *, doc: str = "", constraints: Optional[list[Constraint]] = None
+    ):
+        self._doc: str = doc
+        self._constraints: list[Constraint]
+        if constraints is None:
+            self._constraints = []
+        else:
+            self._constraints = constraints
+
+    @property
+    def doc(self) -> str:
+        """Returns Field's documentation"""
+        return self._doc
+
+    @property
+    def constraints(self) -> list[Constraint[Any]]:
+        """Returns Field's constraints"""
+        return self._constraints

src/dabmodel/__init__.py

@@ -11,11 +11,18 @@ Main module __init__ file.
 """
 
 from .__metadata__ import __version__, __Summuary__, __Name__
-from .model import (
-    DABFieldInfo,
-    DABField,
-    BaseAppliance,
-    BaseFeature,
+
+
+from .LAMFields.LAMField import LAMField
+from .LAMFields.LAMFieldInfo import LAMFieldInfo
+from .LAMFields.FrozenLAMField import FrozenLAMField
+from .LAMFields.LAMCompatible import LAMCompatible
+from .appliance import Appliance
+from .feature import Feature
+from .element import Element
+
+
+from .exception import (
     DABModelException,
     MultipleInheritanceForbidden,
     BrokenInheritance,
@@ -28,7 +35,9 @@ from .model import (
     IncompletelyAnnotatedField,
     ImportForbidden,
     FunctionForbidden,
-    FrozenDABField,
     InvalidFeatureInheritance,
     FeatureNotBound,
+    UnsupportedFieldType,
 )
+
+__all__ = [name for name in globals() if not name.startswith("_")]

src/dabmodel/appliance.py

@@ -0,0 +1,9 @@
+from .element import Element
+from .meta.appliance import _MetaAppliance
+
+
+class Appliance(metaclass=_MetaAppliance):
+    """BaseFeature class
+    Base class for Appliance.
+    An appliance is a server configuration / image that is built using appliance's code and Fields.
+    """

src/dabmodel/element.py

@@ -0,0 +1,7 @@
+from .meta.element import _MetaElement, IElement
+
+
+class Element(IElement, metaclass=_MetaElement):
+    """Element class
+    Base class to apply metaclass and set common Fields.
+    """

src/dabmodel/exception.py

@@ -0,0 +1,109 @@
+class DABModelException(Exception):
+    """DABModelException Exception class
+    Base Exception for DABModelException class
+    """
+
+
+class FunctionForbidden(DABModelException): ...
+
+
+class ExternalCodeForbidden(FunctionForbidden): ...
+
+
+class ClosureForbidden(FunctionForbidden): ...
+
+
+class ReservedFieldName(Exception):
+    """DABModelException Exception class
+    Base Exception for DABModelException class
+    """
+
+
+class MultipleInheritanceForbidden(DABModelException):
+    """MultipleInheritanceForbidden Exception class
+    Multiple inheritance is forbidden when using dabmodel
+    """
+
+
+class BrokenInheritance(DABModelException):
+    """BrokenInheritance Exception class
+    inheritance chain is broken
+    """
+
+
+class ReadOnlyField(DABModelException):
+    """ReadOnlyField Exception class
+    The used Field is ReadOnly
+    """
+
+
+class NewFieldForbidden(DABModelException):
+    """NewFieldForbidden Exception class
+    Field creation is forbidden
+    """
+
+
+class InvalidFieldAnnotation(DABModelException):
+    """InvalidFieldAnnotation Exception class
+    The field annotation is invalid
+    """
+
+
+class InvalidInitializerType(DABModelException):
+    """InvalidInitializerType Exception class
+    The initializer is not a valid type
+    """
+
+
+class NotAnnotatedField(InvalidFieldAnnotation):
+    """NotAnnotatedField Exception class
+    The Field is not Annotated
+    """
+
+
+class IncompletelyAnnotatedField(InvalidFieldAnnotation):
+    """IncompletelyAnnotatedField Exception class
+    The field annotation is incomplete
+    """
+
+
+class UnsupportedFieldType(InvalidFieldAnnotation):
+    """UnsupportedFieldType Exception class
+    The field type is unsupported
+    """
+
+
+class ReadOnlyFieldAnnotation(DABModelException):
+    """ReadOnlyFieldAnnotation Exception class
+    Field annotation connot be modified
+    """
+
+
+class InvalidFieldValue(DABModelException):
+    """InvalidFieldValue Exception class
+    The Field value is invalid
+    """
+
+
+class NonExistingField(DABModelException):
+    """NonExistingField Exception class
+    The given Field is non existing
+    """
+
+
+class ImportForbidden(DABModelException):
+    """ImportForbidden Exception class
+    Imports are forbidden
+    """
+
+
+class InvalidFeatureInheritance(DABModelException):
+    """InvalidFeatureInheritance Exception class
+    Features of same name in child appliance need to be from same type
+    """
+
+
+class FeatureNotBound(DABModelException):
+    """FeatureNotBound Exception class
+    a Feature must be bound to the appliance (or parent)
+    """

src/dabmodel/feature.py

@@ -0,0 +1,12 @@
+from .element import Element
+from .meta.feature import _MetaFeature
+
+
+class Feature(metaclass=_MetaFeature):
+    """Feature class
+    Base class for Appliance's Features.
+    Features are optional traits of an appliance.
+    """
+
+    _BoundAppliance: "Optional[Type[BaseAppliance]]" = None
+    Enabled: bool = False

src/dabmodel/meta/appliance.py

@@ -0,0 +1,213 @@
+from typing import Any, Type
+from copy import copy
+
+from typeguard import check_type, CollectionCheckStrategy, TypeCheckError
+
+from ..tools import LAMdeepfreeze
+from ..LAMFields.LAMField import LAMField
+from ..LAMFields.FrozenLAMField import FrozenLAMField
+from .element import _MetaElement
+from ..feature import Feature
+from ..exception import (
+    InvalidFieldValue,
+    InvalidFeatureInheritance,
+    FeatureNotBound,
+)
+
+
+class _MetaAppliance(_MetaElement):
+    """_MetaAppliance class
+    Appliance specific metaclass code
+    """
+
+    @classmethod
+    def check_class(
+        mcs: type["meta"],
+        name: str,
+        bases: tuple[type[Any], ...],
+        namespace: dict[str, Any],  # pylint: disable=unused-argument
+        extensions: dict[str, Any],
+    ) -> None:
+        """
+        Appliance-specific pre-check: ensure the `features` slot exists in schema.
+
+        Copies the parent's `features` mapping when inheriting to keep it per-class.
+        """
+        super().check_class(name, bases, namespace, extensions)  # type: ignore[misc]
+        if "features" not in namespace["__LAMSchema__"]:
+            namespace["__LAMSchema__"]["features"] = {}
+        else:
+            namespace["__LAMSchema__"]["features"] = copy(
+                namespace["__LAMSchema__"]["features"]
+            )
+
+    @classmethod
+    def process_class_fields(
+        mcs: type["meta"],
+        name: str,
+        bases: tuple[type[Any], ...],
+        namespace: dict[str, Any],
+        extensions: dict[str, Any],
+    ):
+        """
+        Like meta.process_class_fields but also stages Feature declarations.
+
+        Initializes:
+          extensions["new_features"], extensions["modified_features"]
+        then defers to the base scanner for regular fields.
+        """
+        extensions["new_features"] = {}
+        extensions["modified_features"] = {}
+        super().process_class_fields(name, bases, namespace, extensions)  # type: ignore[misc]
+
+    @classmethod
+    def process_new_field(
+        mcs: type["meta"],
+        name: str,
+        bases: tuple[type[Any], ...],
+        namespace: dict[str, Any],
+        _fname: str,
+        _fvalue: Any,
+        extensions: dict[str, Any],
+    ):  # pylint: disable=unused-argument
+        """
+        Intercept Feature declarations.
+
+        - If `_fname` already exists in parent's `features`, enforce same type;
+          stage into `modified_features`.
+        - Else, if `_fvalue` is a Feature *class*, stage into `new_features`.
+        - Otherwise, it is a regular field: delegate to meta.process_new_field.
+        """
+        if _fname in namespace["__LAMSchema__"]["features"].keys():
+            if not issubclass(_fvalue, namespace["__LAMSchema__"]["features"][_fname]):
+                raise InvalidFeatureInheritance(
+                    f"Feature {_fname} is not an instance of {bases[0]}.{_fname}"
+                )
+            extensions["modified_features"][_fname] = _fvalue
+        elif isinstance(_fvalue, type) and issubclass(_fvalue, Feature):
+            extensions["new_features"][_fname] = _fvalue
+        else:
+            super().process_new_field(name, bases, namespace, _fname, _fvalue, extensions)  # type: ignore[misc]
+
+    @classmethod
+    def commit_fields(
+        mcs: type["meta"],
+        cls,
+        name: str,
+        bases: tuple[type[Any], ...],
+        namespace: dict[str, Any],  # pylint: disable=unused-argument
+        extensions: dict[str, Any],
+    ):
+        """
+        Commit regular fields (via meta) and then bind staged Feature classes.
+
+        For each new/modified feature:
+          - bind it to `cls` (sets the feature's `_BoundAppliance`),
+          - register it under `cls.__LAMSchema__["features"]`.
+        """
+        super().commit_fields(cls, name, bases, namespace, extensions)  # type: ignore[misc]
+
+        for _ftname, _ftvalue in extensions["modified_features"].items():
+            _ftvalue._BoundAppliance = cls  # pylint: disable=protected-access
+            cls.__LAMSchema__["features"][_ftname] = _ftvalue
+        for _ftname, _ftvalue in extensions["new_features"].items():
+            _ftvalue._BoundAppliance = cls  # pylint: disable=protected-access
+            cls.__LAMSchema__["features"][_ftname] = _ftvalue
+
+    def finalize_instance(cls: Type, obj, extensions: dict[str, Any]):
+        """
+        Instantiate and attach all features declared (or overridden) in the instance schema.
+        Handles:
+          - Declared features (plain class)
+          - Subclass replacements
+          - Dict overrides (class + patch dict)
+        """
+        for fname, fdef in obj.__LAMSchema__.get("features", {}).items():
+            # Case 1: plain class or subclass
+            if isinstance(fdef, type) and issubclass(fdef, Feature):
+                inst = fdef()
+                object.__setattr__(obj, fname, inst)
+
+            # Case 2: (class, dict) → dict overrides
+            elif isinstance(fdef, tuple) and len(fdef) == 2:
+                feat_cls, overrides = fdef
+                inst = feat_cls()
+                for field_name, new_val in overrides.items():
+                    if field_name not in feat_cls.__LAMSchema__:
+                        raise InvalidFieldValue(
+                            f"Feature '{fname}' has no field '{field_name}'"
+                        )
+                    field = feat_cls.__LAMSchema__[field_name]
+                    try:
+                        check_type(
+                            new_val,
+                            field.annotations,
+                            collection_check_strategy=CollectionCheckStrategy.ALL_ITEMS,
+                        )
+                    except TypeCheckError as exp:
+                        raise InvalidFieldValue(
+                            f"Invalid value for {fname}.{field_name}: "
+                            f"expected {field.annotations}, got {new_val!r}"
+                        ) from exp
+                    object.__setattr__(inst, field_name, LAMdeepfreeze(new_val))
+                    inst.__LAMSchema__[field_name] = FrozenLAMField(
+                        LAMField(field_name, new_val, field.annotations, field._info)
+                    )
+                object.__setattr__(obj, fname, inst)
+
+            else:
+                raise InvalidFieldValue(
+                    f"Invalid feature definition stored for '{fname}': {fdef!r}"
+                )
+
+    def apply_overrides(cls, obj, extensions, *args, **kwargs):
+        """
+        Support for runtime field and feature overrides.
+
+        Fields:
+          MyApp(name="foo")
+
+        Features:
+          MyApp(F1=MyF1)                # inheritance / replacement
+          MyApp(F1={"val": 42, ...})    # dict override of existing feature
+        """
+
+        # --- feature overrides ---
+        for k, v in list(kwargs.items()):
+            if k in cls.__LAMSchema__.get("features", {}):
+                base_feat_cls = cls.__LAMSchema__["features"][k]
+
+                # Case 1: subclass replacement (inheritance)
+                if isinstance(v, type) and issubclass(v, base_feat_cls):
+                    bound = getattr(v, "_BoundAppliance", None)
+                    if bound is None or not issubclass(cls, bound):
+                        raise FeatureNotBound(
+                            f"Feature {v.__name__} is not bound to {cls.__name__}"
+                        )
+                    # record subclass into instance schema
+                    obj.__LAMSchema__["features"][k] = v
+                    kwargs.pop(k)
+
+                # Case 2: dict override
+                elif isinstance(v, dict):
+                    # store (class, override_dict) for finalize_instance
+                    obj.__LAMSchema__["features"][k] = (base_feat_cls, v)
+                    kwargs.pop(k)
+
+                else:
+                    raise InvalidFieldValue(
+                        f"Feature override for '{k}' must be a Feature subclass or dict, got {type(v)}"
+                    )
+
+        # --- new features not declared at class level ---
+        for k, v in list(kwargs.items()):
+            if isinstance(v, type) and issubclass(v, Feature):
+                bound = getattr(v, "_BoundAppliance", None)
+                if bound is None or not issubclass(cls, bound):
+                    raise FeatureNotBound(
+                        f"Feature {v.__name__} is not bound to {cls.__name__}"
+                    )
+                obj.__LAMSchema__["features"][k] = v
+                kwargs.pop(k)
+
+        super().apply_overrides(obj, extensions, *args, **kwargs)

src/dabmodel/meta/feature.py

@@ -0,0 +1,19 @@
+from typing import Type, Any
+from .element import _MetaElement
+from ..exception import FeatureNotBound
+
+
+class _MetaFeature(_MetaElement):
+    """_MetaFeature class
+    Feature specific metaclass code
+    """
+
+    def __call__(cls: Type, *args: Any, **kw: Any):  # intentionally untyped
+        """BaseFeature new instance"""
+
+        if cls._BoundAppliance is None:
+            raise FeatureNotBound()
+
+        obj = super().__call__(*args, **kw)
+
+        return obj

src/dabmodel/tools.py

@@ -1,11 +1,17 @@
 """library's internal tools"""
 
+from typing import Union, List, Any, Dict
 from uuid import UUID
 from datetime import datetime
 import json
 
+from frozendict import deepfreeze
 
-class DABJSONEncoder(json.JSONEncoder):
+JSONPrimitive = Union[str, int, float, bool, None]
+JSONType = Union[JSONPrimitive, List[Any], Dict[str, Any]]  # recursive in practice
+
+
+class LAMJSONEncoder(json.JSONEncoder):
     """allows to JSON encode non supported data type"""
 
     def default(self, o):
@@ -15,3 +21,16 @@ class DABJSONEncoder(json.JSONEncoder):
         if isinstance(o, datetime):
             return str(o)
         return json.JSONEncoder.default(self, o)
+
+
+def LAMdeepfreeze(value):
+    """recursive freeze helper function"""
+    if isinstance(value, dict):
+        return deepfreeze(value)
+    if isinstance(value, set):
+        return frozenset(LAMdeepfreeze(v) for v in value)
+    if isinstance(value, list):
+        return tuple(LAMdeepfreeze(v) for v in value)
+    if isinstance(value, tuple):
+        return tuple(LAMdeepfreeze(v) for v in value)
+    return value

test/test_element.py

@@ -0,0 +1,293 @@
+# dabmodel (c) by chacha
+#
+# dabmodel  is licensed under a
+# Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International Unported License.
+#
+# You should have received a copy of the license along with this
+# work.  If not, see <https://creativecommons.org/licenses/by-nc-sa/4.0/>.
+
+import unittest
+
+import sys
+import subprocess
+from os import chdir, environ
+from pathlib import Path
+
+print(__name__)
+print(__package__)
+
+from src import dabmodel as dm
+
+testdir_path = Path(__file__).parent.resolve()
+chdir(testdir_path.parent.resolve())
+
+
+class ElementTest(unittest.TestCase):
+    def setUp(self):
+        print("\n->", unittest.TestCase.id(self))
+
+    def test_element_simple(self):
+        class E(dm.Element):
+            ivalue: int = 43
+            strvalue: str = "test"
+            fvalue: float = 1.4322
+            ar_int: list[int] = [1, 54, 65]
+            ar_int2: list[int] = [1, 54, 65]
+
+        class A(dm.Appliance):
+            elem: E = E(ivalue=45, strvalue="coucou", ar_int=[5, 7])
+
+        a = A()
+
+        self.assertIsInstance(a.elem, E)
+        self.assertIsInstance(a.elem.ivalue, int)
+        self.assertEqual(a.elem.ivalue, 45)
+        self.assertIsInstance(a.elem.strvalue, str)
+        self.assertEqual(a.elem.strvalue, "coucou")
+        self.assertIsInstance(a.elem.fvalue, float)
+        self.assertEqual(a.elem.fvalue, 1.4322)
+        self.assertIsInstance(a.elem.ar_int, tuple)
+        self.assertEqual(a.elem.ar_int, (5, 7))
+        self.assertIsInstance(a.elem.ar_int2, tuple)
+        self.assertEqual(a.elem.ar_int2, (1, 54, 65))
+
+    def test_element_in_container(self):
+        class E(dm.Element):
+            ivalue: int = 43
+            strvalue: str = "test"
+            fvalue: float = 1.4322
+            ar_int: list[int] = [1, 54, 65]
+            ar_int2: list[int] = [1, 54, 65]
+
+        class A(dm.Appliance):
+            elems: list[E] = [
+                E(ivalue=45, strvalue="coucou", ar_int=[5, 7]),
+                E(ivalue=46, strvalue="coucou2", ar_int=[50, 7]),
+            ]
+
+        a = A()
+
+        self.assertIsInstance(a.elems, tuple)
+        self.assertEqual(len(a.elems), 2)
+
+        self.assertIsInstance(a.elems[0], E)
+        self.assertIsInstance(a.elems[0].ivalue, int)
+        self.assertEqual(a.elems[0].ivalue, 45)
+        self.assertIsInstance(a.elems[0].strvalue, str)
+        self.assertEqual(a.elems[0].strvalue, "coucou")
+        self.assertIsInstance(a.elems[0].fvalue, float)
+        self.assertEqual(a.elems[0].fvalue, 1.4322)
+        self.assertIsInstance(a.elems[0].ar_int, tuple)
+        self.assertEqual(a.elems[0].ar_int, (5, 7))
+        self.assertIsInstance(a.elems[0].ar_int2, tuple)
+        self.assertEqual(a.elems[0].ar_int2, (1, 54, 65))
+
+        self.assertIsInstance(a.elems[1], E)
+        self.assertIsInstance(a.elems[1].ivalue, int)
+        self.assertEqual(a.elems[1].ivalue, 46)
+        self.assertIsInstance(a.elems[1].strvalue, str)
+        self.assertEqual(a.elems[1].strvalue, "coucou2")
+        self.assertIsInstance(a.elems[1].fvalue, float)
+        self.assertEqual(a.elems[1].fvalue, 1.4322)
+        self.assertIsInstance(a.elems[1].ar_int, tuple)
+        self.assertEqual(a.elems[1].ar_int, (50, 7))
+        self.assertIsInstance(a.elems[1].ar_int2, tuple)
+        self.assertEqual(a.elems[1].ar_int2, (1, 54, 65))
+
+    def test_element_frozen(self):
+        class E(dm.Element):
+            ivalue: int = 43
+            strvalue: str = "test"
+            fvalue: float = 1.4322
+            ar_int: list[int] = [1, 54, 65]
+            ar_int2: list[int] = [1, 54, 65]
+
+        class A(dm.Appliance):
+            elems: list[E] = [
+                E(ivalue=45, strvalue="coucou", ar_int=[5, 7]),
+                E(ivalue=46, strvalue="coucou2", ar_int=[50, 7]),
+            ]
+            elem: E = E()
+
+        a = A()
+
+        with self.assertRaises(AttributeError):
+            a.elems.add(E())
+
+        with self.assertRaises(dm.ReadOnlyField):
+            a.elem.ivalue = 1
+
+        with self.assertRaises(dm.ReadOnlyField):
+            a.elems[0].ivalue = 1
+
+    def test_element_inheritance(self):
+        class E(dm.Element):
+            ivalue: int = 43
+            strvalue: str = "test"
+            fvalue: float = 1.4322
+            ar_int: list[int] = [1, 54, 65]
+            ar_int2: list[int] = [1, 54, 65]
+
+        class E2(E):
+            ivalue2: int = 43
+
+        class A(dm.Appliance):
+            elems: list[E] = [
+                E(ivalue=45, strvalue="coucou", ar_int=[5, 7]),
+                E2(ivalue=46, strvalue="coucou2", ar_int=[50, 7], ivalue2=32),
+            ]
+            elem: E = E()
+            elem2: E2 = E2(ivalue=7, ivalue2=33)
+
+        a = A()
+
+        self.assertIsInstance(a.elems, tuple)
+        self.assertEqual(len(a.elems), 2)
+
+        self.assertIsInstance(a.elems[0], E)
+        self.assertIsInstance(a.elems[0].ivalue, int)
+        self.assertEqual(a.elems[0].ivalue, 45)
+        self.assertIsInstance(a.elems[0].strvalue, str)
+        self.assertEqual(a.elems[0].strvalue, "coucou")
+        self.assertIsInstance(a.elems[0].fvalue, float)
+        self.assertEqual(a.elems[0].fvalue, 1.4322)
+        self.assertIsInstance(a.elems[0].ar_int, tuple)
+        self.assertEqual(a.elems[0].ar_int, (5, 7))
+        self.assertIsInstance(a.elems[0].ar_int2, tuple)
+        self.assertEqual(a.elems[0].ar_int2, (1, 54, 65))
+
+        self.assertIsInstance(a.elems[1], E2)
+        self.assertIsInstance(a.elems[1].ivalue, int)
+        self.assertEqual(a.elems[1].ivalue, 46)
+        self.assertIsInstance(a.elems[1].ivalue2, int)
+        self.assertEqual(a.elems[1].ivalue2, 32)
+        self.assertIsInstance(a.elems[1].strvalue, str)
+        self.assertEqual(a.elems[1].strvalue, "coucou2")
+        self.assertIsInstance(a.elems[1].fvalue, float)
+        self.assertEqual(a.elems[1].fvalue, 1.4322)
+        self.assertIsInstance(a.elems[1].ar_int, tuple)
+        self.assertEqual(a.elems[1].ar_int, (50, 7))
+        self.assertIsInstance(a.elems[1].ar_int2, tuple)
+        self.assertEqual(a.elems[1].ar_int2, (1, 54, 65))
+
+        self.assertIsInstance(a.elem, E)
+        self.assertIsInstance(a.elem.ivalue, int)
+        self.assertEqual(a.elem.ivalue, 43)
+        self.assertIsInstance(a.elem.strvalue, str)
+        self.assertEqual(a.elem.strvalue, "test")
+        self.assertIsInstance(a.elem.fvalue, float)
+        self.assertEqual(a.elem.fvalue, 1.4322)
+        self.assertIsInstance(a.elem.ar_int, tuple)
+        self.assertEqual(a.elem.ar_int, (1, 54, 65))
+        self.assertIsInstance(a.elem.ar_int2, tuple)
+        self.assertEqual(a.elem.ar_int2, (1, 54, 65))
+
+        self.assertIsInstance(a.elem2, E2)
+        self.assertIsInstance(a.elem2.ivalue, int)
+        self.assertEqual(a.elem2.ivalue, 7)
+        self.assertIsInstance(a.elem2.ivalue2, int)
+        self.assertEqual(a.elem2.ivalue2, 33)
+        self.assertIsInstance(a.elem2.strvalue, str)
+        self.assertEqual(a.elem2.strvalue, "test")
+        self.assertIsInstance(a.elem2.fvalue, float)
+        self.assertEqual(a.elem2.fvalue, 1.4322)
+        self.assertIsInstance(a.elem2.ar_int, tuple)
+        self.assertEqual(a.elem2.ar_int, (1, 54, 65))
+        self.assertIsInstance(a.elem2.ar_int2, tuple)
+        self.assertEqual(a.elem2.ar_int2, (1, 54, 65))
+
+    def test_element_initializer(self):
+        class E(dm.Element):
+            ivalue: int = 43
+            strvalue: str = "test"
+            fvalue: float = 1.4322
+            ar_int: list[int] = [1, 54, 65]
+            ar_int2: list[int] = [1, 54, 65]
+
+        class A(dm.Appliance):
+            elem: E = E(ivalue=45, strvalue="coucou", ar_int=[5, 7])
+
+            @classmethod
+            def __initializer(self):
+                self.elem = E(ivalue=12, strvalue="coucou", ar_int=[5, 7])
+
+        a = A()
+
+        self.assertIsInstance(a.elem, E)
+        self.assertIsInstance(a.elem.ivalue, int)
+        self.assertEqual(a.elem.ivalue, 12)
+        self.assertIsInstance(a.elem.strvalue, str)
+        self.assertEqual(a.elem.strvalue, "coucou")
+        self.assertIsInstance(a.elem.fvalue, float)
+        self.assertEqual(a.elem.fvalue, 1.4322)
+        self.assertIsInstance(a.elem.ar_int, tuple)
+        self.assertEqual(a.elem.ar_int, (5, 7))
+        self.assertIsInstance(a.elem.ar_int2, tuple)
+        self.assertEqual(a.elem.ar_int2, (1, 54, 65))
+
+    def test_element_in_container_initializer(self):
+        class E(dm.Element):
+            ivalue: int = 43
+            strvalue: str = "test"
+            fvalue: float = 1.4322
+            ar_int: list[int] = [1, 54, 65]
+            ar_int2: list[int] = [1, 54, 65]
+
+        class A(dm.Appliance):
+            elems: list[E] = [E(ivalue=45, strvalue="coucou", ar_int=[5, 7])]
+
+        class B(A):
+            @classmethod
+            def __initializer(cls):
+                cls.elems.append(E(ivalue=46, strvalue="coucou2", ar_int=[50, 7]))
+
+        a = A()
+        b = B()
+
+        self.assertIsInstance(a.elems, tuple)
+        self.assertEqual(len(a.elems), 1)
+
+        self.assertIsInstance(a.elems[0], E)
+        self.assertIsInstance(a.elems[0].ivalue, int)
+        self.assertEqual(a.elems[0].ivalue, 45)
+        self.assertIsInstance(a.elems[0].strvalue, str)
+        self.assertEqual(a.elems[0].strvalue, "coucou")
+        self.assertIsInstance(a.elems[0].fvalue, float)
+        self.assertEqual(a.elems[0].fvalue, 1.4322)
+        self.assertIsInstance(a.elems[0].ar_int, tuple)
+        self.assertEqual(a.elems[0].ar_int, (5, 7))
+        self.assertIsInstance(a.elems[0].ar_int2, tuple)
+        self.assertEqual(a.elems[0].ar_int2, (1, 54, 65))
+
+        self.assertIsInstance(b.elems, tuple)
+        self.assertEqual(len(b.elems), 2)
+
+        self.assertIsInstance(b.elems[0], E)
+        self.assertIsInstance(b.elems[0].ivalue, int)
+        self.assertEqual(b.elems[0].ivalue, 45)
+        self.assertIsInstance(b.elems[0].strvalue, str)
+        self.assertEqual(b.elems[0].strvalue, "coucou")
+        self.assertIsInstance(b.elems[0].fvalue, float)
+        self.assertEqual(b.elems[0].fvalue, 1.4322)
+        self.assertIsInstance(b.elems[0].ar_int, tuple)
+        self.assertEqual(b.elems[0].ar_int, (5, 7))
+        self.assertIsInstance(b.elems[0].ar_int2, tuple)
+        self.assertEqual(b.elems[0].ar_int2, (1, 54, 65))
+
+        self.assertIsInstance(b.elems[1], E)
+        self.assertIsInstance(b.elems[1].ivalue, int)
+        self.assertEqual(b.elems[1].ivalue, 46)
+        self.assertIsInstance(b.elems[1].strvalue, str)
+        self.assertEqual(b.elems[1].strvalue, "coucou2")
+        self.assertIsInstance(b.elems[1].fvalue, float)
+        self.assertEqual(b.elems[1].fvalue, 1.4322)
+        self.assertIsInstance(b.elems[1].ar_int, tuple)
+        self.assertEqual(b.elems[1].ar_int, (50, 7))
+        self.assertIsInstance(b.elems[1].ar_int2, tuple)
+        self.assertEqual(b.elems[1].ar_int2, (1, 54, 65))
+
+
+# ---------- main ----------
+
+if __name__ == "__main__":
+    unittest.main()

test/test_feature.py

@@ -0,0 +1,730 @@
+# dabmodel (c) by chacha
+#
+# dabmodel  is licensed under a
+# Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International Unported License.
+#
+# You should have received a copy of the license along with this
+# work.  If not, see <https://creativecommons.org/licenses/by-nc-sa/4.0/>.
+
+import unittest
+
+from os import chdir
+from pathlib import Path
+
+from typing import (
+    Any,
+    Annotated,
+)
+
+
+print(__name__)
+print(__package__)
+
+from src import dabmodel as dm
+
+
+testdir_path = Path(__file__).parent.resolve()
+chdir(testdir_path.parent.resolve())
+
+
+def test_initializer_safe_testfc():
+    eval("print('hi')")
+
+
+class FeatureTest(unittest.TestCase):
+    def setUp(self):
+        print("\n->", unittest.TestCase.id(self))
+
+    def immutable_vars__test_field(
+        self, obj: Any, name: str, default_value: Any, test_value: Any
+    ):
+        # field is not in the class
+        self.assertNotIn(name, dir(obj.__class__))
+        # field is in the object
+        self.assertIn(name, dir(obj))
+        # field is in the schema
+        self.assertIn(name, obj.__LAMSchema__.keys())
+        # field is readable
+        self.assertEqual(getattr(obj, name), default_value)
+        # field is read only
+        with self.assertRaises(dm.ReadOnlyField):
+            setattr(obj, name, test_value)
+
+    def test_simple(self):
+        """Testing first appliance feature, and Field types (simple)"""
+
+        # class can be created
+        class Appliance1(dm.Appliance):
+            VarStrOuter: str = "testvalue APPLIANCE"
+
+            class Feature1(dm.Feature):
+                VarStrInner: str = "testvalue FEATURE"
+
+        app1 = Appliance1()
+
+        self.assertIsInstance(Appliance1.__LAMSchema__["VarStrOuter"], dm.LAMField)
+        self.assertIsInstance(app1.__LAMSchema__["VarStrOuter"], dm.FrozenLAMField)
+        self.assertIn("Feature1", app1.__LAMSchema__["features"])
+        self.assertIn(
+            "VarStrInner", app1.__LAMSchema__["features"]["Feature1"].__LAMSchema__
+        )
+        self.assertIsInstance(
+            app1.__LAMSchema__["features"]["Feature1"].__LAMSchema__["VarStrInner"],
+            dm.LAMField,
+        )
+        self.assertTrue(hasattr(app1, "Feature1"))
+        self.assertIsInstance(
+            app1.Feature1.__LAMSchema__["VarStrInner"], dm.FrozenLAMField
+        )
+        self.assertTrue(hasattr(app1.Feature1, "VarStrInner"))
+
+    def test_inheritance(self):
+        """Testing first appliance feature, and Field types (simple)"""
+
+        # class can be created
+        class Appliance1(dm.Appliance):
+            VarStrOuter: str = "testvalue APPLIANCE1"
+
+            class Feature1(dm.Feature):
+                VarStrInner: str = "testvalue FEATURE1"
+                VarInt: int = 42
+
+        print(dir(Appliance1))
+
+        class Appliance2(Appliance1):
+            VarStrOuter = "testvalue APPLIANCE2"
+
+            class Feature2(dm.Feature):
+                VarStrInner: str = "testvalue FEATURE2"
+
+        print(dir(Appliance2))
+
+        class Appliance3(Appliance2):
+            VarStrOuter = "testvalue APPLIANCE3"
+
+            class Feature1(Appliance1.Feature1):
+                VarStrInner = "testvalue FEATURE1 modded"
+
+            class Feature3(dm.Feature):
+                VarStrInner: str = "testvalue FEATURE3"
+
+        print(dir(Appliance3))
+
+        app1 = Appliance1()
+        app2 = Appliance2()
+        app3 = Appliance3()
+
+        self.assertIsInstance(Appliance1.__LAMSchema__["VarStrOuter"], dm.LAMField)
+        self.assertIsInstance(app1.__LAMSchema__["VarStrOuter"], dm.FrozenLAMField)
+        self.assertIn("Feature1", app1.__LAMSchema__["features"])
+        self.assertIn(
+            "VarStrInner", app1.__LAMSchema__["features"]["Feature1"].__LAMSchema__
+        )
+        self.assertIsInstance(
+            app1.__LAMSchema__["features"]["Feature1"].__LAMSchema__["VarStrInner"],
+            dm.LAMField,
+        )
+        self.assertTrue(hasattr(app1, "Feature1"))
+        self.assertIsInstance(
+            app1.Feature1.__LAMSchema__["VarStrInner"], dm.FrozenLAMField
+        )
+        self.assertTrue(hasattr(app1.Feature1, "VarStrInner"))
+        self.assertEqual(app1.VarStrOuter, "testvalue APPLIANCE1")
+        self.assertEqual(app1.Feature1.VarStrInner, "testvalue FEATURE1")
+        self.assertEqual(app1.Feature1.VarInt, 42)
+        self.assertEqual(app2.VarStrOuter, "testvalue APPLIANCE2")
+        self.assertEqual(app2.Feature2.VarStrInner, "testvalue FEATURE2")
+        self.assertEqual(app3.VarStrOuter, "testvalue APPLIANCE3")
+        self.assertEqual(app3.Feature1.VarStrInner, "testvalue FEATURE1 modded")
+        self.assertEqual(app3.Feature1.VarInt, 42)
+        self.assertEqual(app3.Feature3.VarStrInner, "testvalue FEATURE3")
+
+    def test_inheritance2(self):
+        """Testing first appliance feature, and Field types (simple)"""
+
+        # class can be created
+        class Appliance1(dm.Appliance):
+            class Feature1(dm.Feature):
+                VarStrInner: str = "testvalue FEATURE1"
+
+        # check cannot REdefine a feature from Feature
+        with self.assertRaises(dm.InvalidFeatureInheritance):
+
+            class Appliance2(Appliance1):
+                class Feature1(dm.Feature): ...
+
+        class Appliance2b(Appliance1):
+            class Feature1(Appliance1.Feature1): ...
+
+        # check only REdefine a feature from highest parent
+        with self.assertRaises(dm.InvalidFeatureInheritance):
+
+            class Appliance3(Appliance2b):
+                class Feature1(Appliance1.Feature1): ...
+
+        class Appliance3b(Appliance2b):
+            class Feature1(Appliance2b.Feature1): ...
+
+        app1 = Appliance1()
+        app2 = Appliance2b()
+        app3 = Appliance3b()
+
+        self.assertEqual(app1.Feature1.VarStrInner, "testvalue FEATURE1")
+        self.assertEqual(app2.Feature1.VarStrInner, "testvalue FEATURE1")
+        self.assertEqual(app3.Feature1.VarStrInner, "testvalue FEATURE1")
+
+        class Appliance4(Appliance3b):
+            class Feature1(Appliance3b.Feature1):
+                VarStrInner = "testvalue FEATURE4"
+
+        self.assertEqual(app1.Feature1.VarStrInner, "testvalue FEATURE1")
+        self.assertEqual(app2.Feature1.VarStrInner, "testvalue FEATURE1")
+        self.assertEqual(app3.Feature1.VarStrInner, "testvalue FEATURE1")
+
+        app4 = Appliance4()
+
+        self.assertEqual(app1.Feature1.VarStrInner, "testvalue FEATURE1")
+        self.assertEqual(app2.Feature1.VarStrInner, "testvalue FEATURE1")
+        self.assertEqual(app3.Feature1.VarStrInner, "testvalue FEATURE1")
+        self.assertEqual(app4.Feature1.VarStrInner, "testvalue FEATURE4")
+
+    def test_register(self):
+        """Testing first appliance feature, and Field types (simple)"""
+
+        # class can be created
+        class Appliance1(dm.Appliance):
+            pass
+
+        class Feature1(dm.Feature):
+            _BoundAppliance = Appliance1
+            VarStrInner: str = "testvalue FEATURE1"
+
+        app = Appliance1(feat1=Feature1)
+        self.assertEqual(app.feat1.VarStrInner, "testvalue FEATURE1")
+
+        # check it does not leak accross instances
+
+        app = Appliance1(feat2=Feature1)
+        self.assertEqual(app.feat2.VarStrInner, "testvalue FEATURE1")
+
+        with self.assertRaises(AttributeError):
+            app.feat1
+
+    def test_register_notbound(self):
+        """Testing first appliance feature, and Field types (simple)"""
+
+        # class can be created
+        class Appliance1(dm.Appliance):
+            pass
+
+        class Feature1(dm.Feature):
+            VarStrInner: str = "testvalue FEATURE1"
+
+        with self.assertRaises(dm.FeatureNotBound):
+            Appliance1(feat1=Feature1)
+
+    def test_register_defect(self):
+
+        class Feature1(dm.Feature):
+            pass
+
+        with self.assertRaises(dm.FeatureNotBound):
+            Feature1()
+
+    def test_new_field_forbidden(self):
+        class App(dm.Appliance):
+            x: int = 1
+
+        app = App()
+        with self.assertRaises(dm.NewFieldForbidden):
+            app.y = 2
+
+    def test_inherit_declared(self):
+        class App(dm.Appliance):
+            class F1(dm.Feature):
+                val: int = 1
+
+        class MyF1(App.F1):
+            val = 2
+            val2: str = "toto"
+
+        app = App(F1=MyF1)
+        self.assertIsInstance(app.F1, MyF1)
+        self.assertEqual(app.F1.val, 2)
+        self.assertEqual(app.F1.val2, "toto")
+
+    def test_override_declared(self):
+        class App(dm.Appliance):
+            class F1(dm.Feature):
+                val: int = 1
+                val2: str = "toto"
+
+        app = App(F1={"val": 42, "val2": "tata"})
+        self.assertEqual(app.F1.val, 42)
+        self.assertEqual(app.F1.val2, "tata")
+
+    def test_dict_override_type_error(self):
+        class App(dm.Appliance):
+            class F1(dm.Feature):
+                val: int = 1
+
+        # wrong type for val → must raise InvalidFieldValue
+        with self.assertRaises(dm.InvalidFieldValue):
+            App(F1={"val": "not-an-int"})
+
+    def test_dict_override_nonexisting_field(self):
+        class App(dm.Appliance):
+            class F1(dm.Feature):
+                val: int = 1
+
+        # field does not exist → must raise
+        with self.assertRaises(dm.InvalidFieldValue):
+            App(F1={"doesnotexist": 123})
+
+    def test_inheritance_with_extra_fields(self):
+        class App(dm.Appliance):
+            class F1(dm.Feature):
+                val: int = 1
+
+        class MyF1(App.F1):
+            val = 2
+            extra: str = "hello"
+
+        app = App(F1=MyF1)
+        self.assertEqual(app.F1.val, 2)
+        self.assertEqual(app.F1.extra, "hello")
+
+    def test_not_bound_runtime_attach_fails(self):
+        class App(dm.Appliance):
+            pass
+
+        class UnboundFeature(dm.Feature):
+            x: int = 1
+
+        # attaching an unbound feature should raise
+        with self.assertRaises(dm.FeatureNotBound):
+            App(Unbound=UnboundFeature)
+
+    def test_override_does_not_leak_between_instances(self):
+        class App(dm.Appliance):
+            class F1(dm.Feature):
+                val: int = 1
+
+        app1 = App(F1={"val": 99})
+        app2 = App()
+        self.assertEqual(app1.F1.val, 99)
+        self.assertEqual(app2.F1.val, 1)
+
+    def test_deepfreeze_nested_mixed_tuple_list(self):
+        class App(dm.Appliance):
+            data: tuple[list[int], tuple[int, list[int]]] = ([1, 2], (3, [4, 5]))
+
+        app = App()
+
+        # Top-level: must be tuple
+        self.assertIsInstance(app.data, tuple)
+
+        # First element of tuple: should have been frozen to tuple, not list
+        self.assertIsInstance(app.data[0], tuple)
+
+        # Nested second element: itself a tuple
+        self.assertIsInstance(app.data[1], tuple)
+
+        # Deepest element: inner list should also be frozen to tuple
+        self.assertIsInstance(app.data[1][1], tuple)
+
+        # Check immutability
+        with self.assertRaises(TypeError):
+            app.data[0] += (99,)  # tuples are immutable
+
+        with self.assertRaises(TypeError):
+            app.data[1][1] += (42,)  # inner tuple also immutable
+
+    def test_inacurate_type(self):
+        with self.assertRaises(dm.InvalidFieldAnnotation):
+
+            class Appliance1(dm.Appliance):
+                SomeVar: list = []
+
+        with self.assertRaises(dm.InvalidFieldAnnotation):
+
+            class Appliance2(dm.Appliance):
+                SomeVar: list[Any] = []
+
+        with self.assertRaises(dm.InvalidFieldAnnotation):
+
+            class Appliance3(dm.Appliance):
+                SomeVar: list[object] = []
+
+        with self.assertRaises(dm.InvalidFieldAnnotation):
+
+            class Appliance4(dm.Appliance):
+                SomeVar: dict = {}
+
+        with self.assertRaises(dm.InvalidFieldAnnotation):
+
+            class Appliance5(dm.Appliance):
+                SomeVar: dict[str, Any] = {}
+
+        with self.assertRaises(dm.InvalidFieldAnnotation):
+
+            class Appliance6(dm.Appliance):
+                SomeVar: dict[Any, Any] = {}
+
+        with self.assertRaises(dm.InvalidFieldAnnotation):
+
+            class Appliance7(dm.Appliance):
+                SomeVar: dict[Any, str] = {}
+
+        with self.assertRaises(dm.InvalidFieldAnnotation):
+
+            class Appliance8(dm.Appliance):
+                SomeVar: dict[str, object] = {}
+
+    def test_runtime_attach_bound_success(self):
+        class App(dm.Appliance):
+            class F1(dm.Feature):
+                val: int = 1
+
+        class Extra(App.F1):  # stays bound to App
+            val = 7
+
+        app = App(Extra=Extra)
+        self.assertTrue(hasattr(app, "Extra"))
+        self.assertIsInstance(app.Extra, Extra)
+        self.assertEqual(app.Extra.val, 7)
+
+    def test_cant_override_inherited_annotation(self):
+        class App(dm.Appliance):
+            class F1(dm.Feature):
+                val: int = 1
+
+        with self.assertRaises(dm.ReadOnlyFieldAnnotation):
+
+            class Extra(App.F1):
+                val: str = "test"
+
+    def test_fields_are_frozen_after_override(self):
+        class App(dm.Appliance):
+            class F(dm.Feature):
+                nums: list[int] = [1, 2]
+                tag: str = "x"
+
+        # dict override
+        app1 = App(F={"nums": [9], "tag": "y"})
+        self.assertEqual(app1.F.nums, (9,))
+        self.assertEqual(app1.F.tag, "y")
+        with self.assertRaises(AttributeError):
+            app1.F.nums.append(3)  # tuple
+
+        # subclass override
+        class F2(App.F):
+            nums = [4, 5]
+
+        app2 = App(F=F2)
+        self.assertEqual(app2.F.nums, (4, 5))
+        with self.assertRaises(dm.ReadOnlyField):
+            app2.F.nums += (6,)  # still immutable
+
+    def test_dict_partial_override_keeps_other_defaults(self):
+        class App(dm.Appliance):
+            class F(dm.Feature):
+                a: int = 1
+                b: str = "k"
+
+        app = App(F={"b": "z"})
+        self.assertEqual(app.F.a, 1)  # default remains
+        self.assertEqual(app.F.b, "z")  # overridden
+
+    def test_override_linear_chain(self):
+        # Base appliance defines Feat1
+        class A(dm.Appliance):
+            class Feat1(dm.Feature):
+                x: int = 1
+
+        # ✅ Appliance B overrides Feat1 by subclassing A.Feat1
+        class B(A):
+            class Feat1(A.Feat1):
+                y: int = 2
+
+        self.assertTrue(issubclass(B.Feat1, A.Feat1))
+
+        # ✅ Appliance C overrides Feat1 again by subclassing B.Feat1 (not A.Feat1)
+        class C(B):
+            class Feat1(B.Feat1):
+                z: int = 3
+
+        self.assertTrue(issubclass(C.Feat1, B.Feat1))
+        self.assertTrue(issubclass(C.Feat1, A.Feat1))
+
+        # ❌ Bad: D tries to override with a *fresh* Feature, not subclass of B.Feat1
+        with self.assertRaises(dm.InvalidFeatureInheritance):
+
+            class D(B):
+                class Feat1(dm.Feature):
+                    fail: str = "oops"
+
+        # ❌ Bad: E tries to override with ancestor (A.Feat1) instead of B.Feat1
+        with self.assertRaises(dm.InvalidFeatureInheritance):
+
+            class E(B):
+                class Feat1(A.Feat1):
+                    fail: str = "oops"
+
+        # ✅ New feature name in child is always fine
+        class F(B):
+            class Feat2(dm.Feature):
+                other: str = "ok"
+
+        self.assertTrue(hasattr(F, "Feat2"))
+
+    def test_override_chain_runtime_replacement(self):
+        # Build a linear chain: A -> B -> C for feature 'Feat1'
+        class A(dm.Appliance):
+            class Feat1(dm.Feature):
+                x: int = 1
+
+        class B(A):
+            class Feat1(A.Feat1):
+                y: int = 2
+
+        class C(B):
+            class Feat1(B.Feat1):
+                z: int = 3
+
+        # ✅ OK: at instantiation of C, replacing Feat1 with a subclass of the LATEST (C.Feat1)
+        class CFeat1Plus(C.Feat1):
+            w: int = 4
+
+        c_ok = C(Feat1=CFeat1Plus)
+        self.assertIsInstance(c_ok.Feat1, CFeat1Plus)
+        self.assertEqual(
+            (c_ok.Feat1.x, c_ok.Feat1.y, c_ok.Feat1.z, c_ok.Feat1.w), (1, 2, 3, 4)
+        )
+
+        # ❌ Not OK: replacing with a subclass of the ancestor (A.Feat1) — must target latest (C.Feat1)
+        class AFeat1Alt(A.Feat1):
+            pass
+
+        with self.assertRaises(dm.InvalidFieldValue):
+            C(Feat1=AFeat1Alt)
+
+        # ❌ Not OK: replacing with a subclass of the mid ancestor (B.Feat1) — still must target latest (C.Feat1)
+        class BFeat1Alt(B.Feat1):
+            pass
+
+        with self.assertRaises(dm.InvalidFieldValue):
+            C(Feat1=BFeat1Alt)
+
+    def test_inheritance_tree_and_no_leakage(self):
+        class A(dm.Appliance):
+            class F1(dm.Feature):
+                a: int = 1
+
+            class F2(dm.Feature):
+                b: int = 2
+
+        # ✅ Child inherits both features automatically
+        class B(A):
+            c: str = "extra"
+
+        b1 = B()
+        self.assertIsInstance(b1.F1, A.F1)
+        self.assertIsInstance(b1.F2, A.F2)
+        self.assertEqual((b1.F1.a, b1.F2.b, b1.c), (1, 2, "extra"))
+
+        # ✅ Override only F2, F1 should still come from A
+        class C(B):
+            class F2(B.F2):
+                bb: int = 22
+
+        c1 = C()
+        self.assertIsInstance(c1.F1, A.F1)  # unchanged
+        self.assertIsInstance(c1.F2, C.F2)  # overridden
+        self.assertEqual((c1.F1.a, c1.F2.b, c1.F2.bb), (1, 2, 22))
+
+        # ✅ No leakage: instances of B are not affected by C's override
+        b2 = B()
+        self.assertIsInstance(b2.F2, A.F2)
+        self.assertFalse(hasattr(b2.F2, "bb"))
+
+        # ✅ Adding a new feature in D is independent of previous appliances
+        class D(C):
+            class F3(dm.Feature):
+                d: int = 3
+
+        d1 = D()
+        self.assertIsInstance(d1.F1, A.F1)
+        self.assertIsInstance(d1.F2, C.F2)
+        self.assertIsInstance(d1.F3, D.F3)
+
+        # ✅ No leakage: instances of A and B should not see F3
+        a1 = A()
+        self.assertFalse(hasattr(a1, "F3"))
+        b3 = B()
+        self.assertFalse(hasattr(b3, "F3"))
+
+    def test_appliance_inheritance_tree_isolation(self):
+        class A(dm.Appliance):
+            class F1(dm.Feature):
+                a: int = 1
+
+        # Branch 1 overrides F1
+        class B(A):
+            class F1(A.F1):
+                b: int = 2
+
+        # Branch 2 also overrides F1 differently
+        class C(A):
+            class F1(A.F1):
+                c: int = 3
+
+        # ✅ Instances of B use B.F1
+        b = B()
+        self.assertIsInstance(b.F1, B.F1)
+        self.assertEqual((b.F1.a, b.F1.b), (1, 2))
+        self.assertFalse(hasattr(b.F1, "c"))
+
+        # ✅ Instances of C use C.F1
+        c = C()
+        self.assertIsInstance(c.F1, C.F1)
+        self.assertEqual((c.F1.a, c.F1.c), (1, 3))
+        self.assertFalse(hasattr(c.F1, "b"))
+
+        # ✅ Base appliance A still uses its original feature
+        a = A()
+        self.assertIsInstance(a.F1, A.F1)
+        self.assertEqual(a.F1.a, 1)
+        self.assertFalse(hasattr(a.F1, "b"))
+        self.assertFalse(hasattr(a.F1, "c"))
+
+        # ✅ No leakage: B's override doesn't affect C and vice versa
+        b2 = B()
+        c2 = C()
+        self.assertTrue(hasattr(b2.F1, "b"))
+        self.assertFalse(hasattr(b2.F1, "c"))
+        self.assertTrue(hasattr(c2.F1, "c"))
+        self.assertFalse(hasattr(c2.F1, "b"))
+
+    def test_appliance_inheritance_tree_runtime_attach_isolation(self):
+        class A(dm.Appliance):
+            class F1(dm.Feature):
+                a: int = 1
+
+        class B(A):
+            class F1(A.F1):
+                b: int = 2
+
+        class C(A):
+            class F1(A.F1):
+                c: int = 3
+
+        # Define new runtime-attachable features
+        class FextraB(B.F1):
+            xb: int = 99
+
+        class FextraC(C.F1):
+            xc: int = -99
+
+        # ✅ Attach to B at instantiation
+        b = B(F1=FextraB)
+        self.assertIsInstance(b.F1, FextraB)
+        self.assertEqual((b.F1.a, b.F1.b, b.F1.xb), (1, 2, 99))
+        self.assertFalse(hasattr(b.F1, "c"))
+        self.assertFalse(hasattr(b.F1, "xc"))
+
+        # ✅ Attach to C at instantiation
+        c = C(F1=FextraC)
+        self.assertIsInstance(c.F1, FextraC)
+        self.assertEqual((c.F1.a, c.F1.c, c.F1.xc), (1, 3, -99))
+        self.assertFalse(hasattr(c.F1, "b"))
+        self.assertFalse(hasattr(c.F1, "xb"))
+
+        # ✅ Base appliance still untouched
+        a = A()
+        self.assertIsInstance(a.F1, A.F1)
+        self.assertEqual(a.F1.a, 1)
+        self.assertFalse(hasattr(a.F1, "b"))
+        self.assertFalse(hasattr(a.F1, "c"))
+        self.assertFalse(hasattr(a.F1, "xb"))
+        self.assertFalse(hasattr(a.F1, "xc"))
+
+        # ✅ Repeated instantiations stay isolated
+        b2 = B()
+        c2 = C()
+        self.assertIsInstance(b2.F1, B.F1)
+        self.assertIsInstance(c2.F1, C.F1)
+        self.assertFalse(hasattr(b2.F1, "xb"))
+        self.assertFalse(hasattr(c2.F1, "xc"))
+
+    def test_feature_dict_override_with_nested_containers(self):
+        class App(dm.Appliance):
+            class F1(dm.Feature):
+                values: list[int] = [1, 2]
+
+        app = App(F1={"values": [5, 6]})
+        self.assertEqual(app.F1.values, (5, 6))  # deepfreeze → tuple
+
+        # Invalid type in list should fail
+        with self.assertRaises(dm.InvalidFieldValue):
+            App(F1={"values": [1, "oops"]})
+
+    def test_dict_override_with_unknown_key(self):
+        class App(dm.Appliance):
+            class F1(dm.Feature):
+                a: int = 1
+
+        # Dict override with unknown field 'zzz'
+        with self.assertRaises(dm.InvalidFieldValue):
+            App(F1={"zzz": 42})
+
+    def test_schema_isolation_across_multiple_overrides(self):
+        class App(dm.Appliance):
+            class F1(dm.Feature):
+                a: int = 1
+
+        class F1a(App.F1):
+            a = 10
+
+        class F1b(App.F1):
+            a = 20
+
+        app1 = App(F1=F1a)
+        self.assertIsInstance(app1.F1, F1a)
+        self.assertEqual(app1.F1.a, 10)
+
+        app2 = App(F1=F1b)
+        self.assertIsInstance(app2.F1, F1b)
+        self.assertEqual(app2.F1.a, 20)
+
+        # Original appliance schema must not be polluted
+        app3 = App()
+        self.assertIsInstance(app3.F1, App.F1)
+        self.assertEqual(app3.F1.a, 1)
+
+    def test_inheritance_with_annotated_fields(self):
+
+        class App(dm.Appliance):
+            class F1(dm.Feature):
+                a: Annotated[int, dm.LAMFieldInfo(doc="field a")] = 1
+
+        # ✅ Subclass override must inherit from parent F1
+        class F1Ex(App.F1):
+            b: str = "ok"
+
+        app = App(F1=F1Ex)
+        self.assertIsInstance(app.F1, F1Ex)
+        self.assertEqual((app.F1.a, app.F1.b), (1, "ok"))
+
+        # ❌ Wrong: fresh Feature under same name
+        with self.assertRaises(dm.InvalidFeatureInheritance):
+
+            class Bad(App):
+                class F1(dm.Feature):
+                    fail: str = "oops"
+
+
+# ---------- main ----------
+
+if __name__ == "__main__":
+    unittest.main()