Added test coverage.

Author: kmvanbrunt

cmd2/argparse_custom.py

@@ -371,11 +371,11 @@ def register_argparse_argument_parameter(
                       It accepts the Action instance and the value as arguments.
     """
     if not param_name.isidentifier():
-        raise KeyError(f'Invalid parameter name {param_name} - cannot be used as a python identifier')
+        raise KeyError(f"Invalid parameter name '{param_name}' - cannot be used as a python identifier")
 
     attr_name = constants.cmd2_attr_name(param_name)
     if param_name in CUSTOM_ACTION_ATTRIBS or hasattr(argparse.Action, attr_name):
-        raise KeyError(f'Custom parameter {param_name} already exists')
+        raise KeyError(f"Custom parameter '{param_name}' already exists")
 
     def _action_get_custom_parameter(self: argparse.Action) -> Any:
         """Get the custom attribute of an argparse Action."""

tests/test_argparse_custom.py

@@ -9,12 +9,14 @@
 from cmd2 import (
     Choices,
     Cmd2ArgumentParser,
+    argparse_custom,
     constants,
 )
 from cmd2.argparse_custom import (
     Cmd2HelpFormatter,
     Cmd2RichArgparseConsole,
     generate_range_error,
+    register_argparse_argument_parameter,
 )
 
 from .conftest import run_cmd
@@ -296,6 +298,19 @@ def test_cmd2_attribute_wrapper() -> None:
     assert wrapper.get() == new_val
 
 
+def test_register_argparse_argument_parameter() -> None:
+    register_argparse_argument_parameter("test")
+    assert "test" in argparse_custom.CUSTOM_ACTION_ATTRIBS
+
+    expected_err = "already exists"
+    with pytest.raises(KeyError, match=expected_err):
+        register_argparse_argument_parameter("test")
+
+    expected_err = "Invalid parameter name"
+    with pytest.raises(KeyError, match=expected_err):
+        register_argparse_argument_parameter("invalid name")
+
+
 def test_parser_attachment() -> None:
     # Attach a parser as a subcommand
     root_parser = Cmd2ArgumentParser(description="root command")