Fix confusing issue when config class names don't end with Config.

src/programming/BL_Python/programming/config/__init__.py

@@ -4,6 +4,10 @@
 
 import toml
 from BL_Python.programming.collections.dict import AnyDict, merge
+from BL_Python.programming.config.exceptions import (
+    ConfigBuilderStateError,
+    NotEndsWithConfigError,
+)
 
 TConfig = TypeVar("TConfig")
 
@@ -29,24 +33,24 @@ def build(self) -> type[TConfig]:
             return self._root_config
 
         if not self._configs:
-            raise Exception("Cannot build a config without any configs.")
+            raise ConfigBuilderStateError(
+                "Cannot build a config without any base config types specified."
+            )
 
         _new_type_base = self._root_config if self._root_config else object
 
         attrs: dict[Any, Any] = {}
         annotations: dict[str, Any] = {}
 
         for config in self._configs:
-            try:
-                config_name = config.__name__[
-                    : config.__name__.rindex("Config")
-                ].lower()
-                annotations[config_name] = config
-                attrs[config_name] = None
-            except ValueError as e:
-                raise ValueError(
+            if not config.__name__.endswith("Config"):
+                raise NotEndsWithConfigError(
                     f"Class name '{config.__name__}' is not a valid config class. The name must end with 'Config'"
-                ) from e
+                )
+
+            config_name = config.__name__[: config.__name__.rindex("Config")].lower()
+            annotations[config_name] = config
+            attrs[config_name] = None
 
         attrs["__annotations__"] = annotations
         # make one type that has the names of the config objects

src/programming/BL_Python/programming/config/exceptions.py

@@ -0,0 +1,10 @@
+class InvalidConfigNameError(Exception):
+    """The class name used as a configuration type is invalid."""
+
+
+class NotEndsWithConfigError(InvalidConfigNameError):
+    """The name must end with `Config`."""
+
+
+class ConfigBuilderStateError(Exception):
+    """The config builder has not been configured correctly."""

src/programming/test/unit/test_config.py

@@ -0,0 +1,130 @@
+import pytest
+from BL_Python.programming.config import AbstractConfig, ConfigBuilder, load_config
+from BL_Python.programming.config.exceptions import (
+    ConfigBuilderStateError,
+    NotEndsWithConfigError,
+)
+from pydantic import BaseModel
+from pytest_mock import MockerFixture
+
+
+class FooConfig(BaseModel):
+    value: str
+    other_value: bool = False
+
+
+class BarConfig(BaseModel):
+    value: str
+
+
+class BazConfig(BaseModel, AbstractConfig):
+    value: str
+
+
+class TestConfig(BaseModel, AbstractConfig):
+    foo: FooConfig = FooConfig(value="xyz")
+    bar: BarConfig | None = None
+
+
+class InvalidConfigClass(BaseModel, AbstractConfig):
+    pass
+
+
+def test__Config__load_config__reads_toml_file(mocker: MockerFixture):
+    fake_config_dict = {}
+    toml_mock = mocker.patch("toml.load", return_value=fake_config_dict)
+    _ = load_config(TestConfig, "foo.toml")
+    assert toml_mock.called
+
+
+def test__Config__load_config__initializes_section_config_value(mocker: MockerFixture):
+    fake_config_dict = {"foo": {"value": "abc123"}}
+    _ = mocker.patch("io.open")
+    _ = mocker.patch("toml.decoder.loads", return_value=fake_config_dict)
+    config = load_config(TestConfig, "foo.toml")
+    assert config.foo.value == "abc123"
+
+
+def test__Config__load_config__initializes_section_config(mocker: MockerFixture):
+    fake_config_dict = {"bar": {"value": "abc123"}}
+    _ = mocker.patch("io.open")
+    _ = mocker.patch("toml.decoder.loads", return_value=fake_config_dict)
+    config = load_config(TestConfig, "foo.toml")
+    assert config.bar is not None
+    assert config.bar.value == "abc123"
+
+
+def test__Config__load_config__applies_overrides(mocker: MockerFixture):
+    fake_config_dict = {"foo": {"value": "abc123"}}
+    override_config_dict = {"foo": {"value": "XYZ"}}
+    _ = mocker.patch("io.open")
+    _ = mocker.patch("toml.decoder.loads", return_value=fake_config_dict)
+    config = load_config(TestConfig, "foo.toml", override_config_dict)
+    assert config.foo.value == override_config_dict["foo"]["value"]
+
+
+def test__ConfigBuilder__build__raises_error_when_no_root_config_and_no_section_configs_specified():
+    config_builder = ConfigBuilder[TestConfig]()
+    with pytest.raises(ConfigBuilderStateError):
+        _ = config_builder.build()
+
+
+def test__ConfigBuilder__build__raises_error_when_section_class_name_is_invalid():
+    config_builder = ConfigBuilder[TestConfig]()
+    _ = config_builder.with_configs([InvalidConfigClass])
+    with pytest.raises(NotEndsWithConfigError):
+        _ = config_builder.build()
+
+
+def test__ConfigBuilder__build__uses_object_as_root_config_when_no_root_config_specified():
+    config_builder = ConfigBuilder[TestConfig]()
+    _ = config_builder.with_configs([BazConfig])
+    config_type = config_builder.build()
+    assert TestConfig not in config_type.__mro__
+    assert BazConfig not in config_type.__mro__
+    assert hasattr(config_type, "baz")
+    assert hasattr(config_type(), "baz")
+
+
+def test__ConfigBuilder__build__uses_root_config_when_no_section_configs_specified():
+    config_builder = ConfigBuilder[TestConfig]()
+    _ = config_builder.with_root_config(TestConfig)
+    config_type = config_builder.build()
+    assert config_type is TestConfig
+    assert isinstance(config_type(), TestConfig)
+
+
+def test__ConfigBuilder__build__creates_config_type_when_multiple_configs_specified(
+    mocker: MockerFixture,
+):
+    fake_config_dict = {"baz": {"value": "ABC"}}
+    _ = mocker.patch("io.open")
+    _ = mocker.patch("toml.decoder.loads", return_value=fake_config_dict)
+
+    config_builder = ConfigBuilder[TestConfig]()
+    _ = config_builder.with_root_config(TestConfig)
+    _ = config_builder.with_configs([BazConfig])
+    config_type = config_builder.build()
+    config = load_config(config_type, "foo.toml")
+
+    assert TestConfig in config_type.__mro__
+    assert hasattr(config, "baz")
+
+
+def test__ConfigBuilder__build__sets_dynamic_config_values_when_multiple_configs_specified(
+    mocker: MockerFixture,
+):
+    fake_config_dict = {"baz": {"value": "ABC"}}
+    _ = mocker.patch("io.open")
+    _ = mocker.patch("toml.decoder.loads", return_value=fake_config_dict)
+
+    config_builder = ConfigBuilder[TestConfig]()
+    _ = config_builder.with_root_config(TestConfig)
+    _ = config_builder.with_configs([BazConfig])
+    config_type = config_builder.build()
+    config = load_config(config_type, "foo.toml")
+
+    assert hasattr(config, "baz")
+    assert getattr(config, "baz")
+    assert getattr(getattr(config, "baz"), "value")
+    assert getattr(getattr(config, "baz"), "value") == "ABC"