diff --git a/test/core/configuration/__init__.py b/test/core/configuration/__init__.py
new file mode 100644
index 00000000..e69de29b
diff --git a/test/core/configuration/configuration_model_abc_test.py b/test/core/configuration/configuration_model_abc_test.py
new file mode 100644
index 00000000..f51a3890
--- /dev/null
+++ b/test/core/configuration/configuration_model_abc_test.py
@@ -0,0 +1,130 @@
+import os
+import pytest
+from cpl.core.configuration.configuration_model_abc import ConfigurationModelABC
+
+
+class DatabaseSettings(ConfigurationModelABC):
+    def __init__(self, src: dict = None):
+        ConfigurationModelABC.__init__(self, src or {})
+        self.option("host", str, default="localhost")
+        self.option("port", int, default=5432)
+        self.option("name", str)
+        self.option("debug", bool, default=False)
+
+
+class RequiredSettings(ConfigurationModelABC):
+    def __init__(self, src: dict = None):
+        ConfigurationModelABC.__init__(self, src or {})
+        self.option("api_key", str, required=True)
+
+
+class MutableSettings(ConfigurationModelABC):
+    def __init__(self, src: dict = None):
+        ConfigurationModelABC.__init__(self, src or {}, readonly=False)
+        self.option("value", str, default="initial")
+
+
+class EnvSettings(ConfigurationModelABC):
+    def __init__(self, src: dict = None):
+        ConfigurationModelABC.__init__(self, src or {}, env_prefix="MYAPP")
+        self.option("secret", str, default=None)
+
+
+# --- option() / defaults ---
+
+def test_default_values():
+    s = DatabaseSettings()
+    assert s.host == "localhost"
+    assert s.port == 5432
+    assert s.debug is False
+
+
+def test_values_from_src():
+    # NOTE: passing native bool True via src triggers cast(True, bool) which
+    # fails because cast() calls value.lower() on a bool (bug in cast.py).
+    # Use string "true" instead — matches real JSON-parsed values.
+    s = DatabaseSettings({"host": "db.example.com", "port": 3306, "name": "mydb", "debug": "true"})
+    assert s.host == "db.example.com"
+    assert s.port == 3306
+    assert s.name == "mydb"
+    assert s.debug is True
+
+
+def test_pascal_case_key():
+    s = DatabaseSettings({"Host": "remotehost", "Port": 1234})
+    assert s.host == "remotehost"
+    assert s.port == 1234
+
+
+def test_snake_case_key():
+    s = DatabaseSettings({"host": "snakehost"})
+    assert s.host == "snakehost"
+
+
+def test_missing_optional_is_none():
+    s = DatabaseSettings()
+    assert s.name is None
+
+
+def test_type_casting_int():
+    s = DatabaseSettings({"port": "9999"})
+    assert s.port == 9999
+    assert isinstance(s.port, int)
+
+
+def test_type_casting_bool():
+    s = DatabaseSettings({"debug": "true"})
+    assert s.debug is True
+
+
+# --- required ---
+
+def test_required_field_present():
+    s = RequiredSettings({"api_key": "abc123"})
+    assert s.api_key == "abc123"
+
+
+def test_required_field_missing_raises():
+    with pytest.raises(ValueError, match="required"):
+        RequiredSettings()
+
+
+# --- readonly ---
+
+def test_readonly_raises_on_setattr():
+    s = DatabaseSettings()
+    with pytest.raises(AttributeError, match="read-only"):
+        s.host = "newhost"
+
+
+def test_mutable_settings_can_be_set():
+    s = MutableSettings()
+    s.value = "changed"
+    assert s.value == "changed"
+
+
+# --- env override ---
+
+def test_env_prefix_override(monkeypatch):
+    monkeypatch.setenv("MYAPP_SECRET", "env_secret_value")
+    s = EnvSettings()
+    assert s.secret == "env_secret_value"
+
+
+def test_env_no_prefix_override(monkeypatch):
+    monkeypatch.setenv("HOST", "env_host")
+
+    class NoPrefix(ConfigurationModelABC):
+        def __init__(self, src=None):
+            ConfigurationModelABC.__init__(self, src or {})
+            self.option("host", str, default=None)
+
+    s = NoPrefix()
+    assert s.host == "env_host"
+
+
+# --- cannot instantiate ABC ---
+
+def test_cannot_instantiate_abc_directly():
+    with pytest.raises(TypeError):
+        ConfigurationModelABC()
diff --git a/test/core/configuration/configuration_test.py b/test/core/configuration/configuration_test.py
new file mode 100644
index 00000000..99f79f2e
--- /dev/null
+++ b/test/core/configuration/configuration_test.py
@@ -0,0 +1,107 @@
+import json
+import os
+import pytest
+from cpl.core.configuration.configuration import Configuration
+from cpl.core.configuration.configuration_model_abc import ConfigurationModelABC
+
+
+class AppSettings(ConfigurationModelABC):
+    def __init__(self, src: dict = None):
+        ConfigurationModelABC.__init__(self, src or {})
+        self.option("app_name", str, default="default-app")
+        self.option("version", str, default="0.0.0")
+
+
+class ServerSettings(ConfigurationModelABC):
+    def __init__(self, src: dict = None):
+        ConfigurationModelABC.__init__(self, src or {})
+        self.option("host", str, default="localhost")
+        self.option("port", int, default=8080)
+
+
+@pytest.fixture(autouse=True)
+def clear_config():
+    """Reset Configuration state before each test."""
+    Configuration._config.clear()
+    yield
+    Configuration._config.clear()
+
+
+# --- set / get ---
+
+def test_set_and_get_by_class():
+    settings = AppSettings({"app_name": "TestApp", "version": "1.0.0"})
+    Configuration.set(AppSettings, settings)
+    result = Configuration.get(AppSettings)
+    assert result.app_name == "TestApp"
+    assert result.version == "1.0.0"
+
+
+def test_set_and_get_by_string_key():
+    Configuration.set("my_key", "my_value")
+    assert Configuration.get("my_key") == "my_value"
+
+
+def test_get_missing_returns_default():
+    assert Configuration.get("nonexistent", "fallback") == "fallback"
+
+
+def test_get_missing_returns_none():
+    assert Configuration.get("nonexistent") is None
+
+
+def test_get_model_auto_instantiates():
+    # Getting an unregistered ConfigurationModelABC subclass should auto-create it
+    result = Configuration.get(ServerSettings)
+    assert isinstance(result, ServerSettings)
+    assert result.host == "localhost"
+    assert result.port == 8080
+
+
+def test_overwrite_existing():
+    Configuration.set("key", "first")
+    Configuration.set("key", "second")
+    assert Configuration.get("key") == "second"
+
+
+def test_multiple_models():
+    Configuration.set(AppSettings, AppSettings({"app_name": "App"}))
+    Configuration.set(ServerSettings, ServerSettings({"port": 9000}))
+    assert Configuration.get(AppSettings).app_name == "App"
+    assert Configuration.get(ServerSettings).port == 9000
+
+
+# --- add_json_file ---
+
+def test_add_json_file_loads_model(tmp_path):
+    config_data = {"AppSettings": {"app_name": "FromFile", "version": "2.0.0"}}
+    config_file = tmp_path / "appsettings.json"
+    config_file.write_text(json.dumps(config_data), encoding="utf-8")
+
+    Configuration.add_json_file(str(config_file), output=False)
+
+    result = Configuration.get(AppSettings)
+    assert result.app_name == "FromFile"
+    assert result.version == "2.0.0"
+
+
+def test_add_json_file_not_found_exits(tmp_path):
+    with pytest.raises(SystemExit):
+        Configuration.add_json_file(str(tmp_path / "missing.json"), output=False)
+
+
+def test_add_json_file_optional_missing_returns_none(tmp_path):
+    result = Configuration.add_json_file(
+        str(tmp_path / "missing.json"), optional=True, output=False
+    )
+    assert result is None
+
+
+def test_add_json_file_invalid_json(tmp_path):
+    # _load_json_file catches parse errors and returns {} — no SystemExit.
+    # add_json_file then proceeds with an empty config (no models loaded).
+    bad_file = tmp_path / "bad.json"
+    bad_file.write_text("not valid json", encoding="utf-8")
+    Configuration.add_json_file(str(bad_file), output=False)
+    # No model should be registered since the file was invalid
+    assert Configuration.get("AppSettings") is None