Add test cases for commands implemented as asynchronous methods

Author: KanchiShimono

tests/test_source_cli.py

@@ -1,4 +1,5 @@
 import argparse
+import asyncio
 import re
 import sys
 import time
@@ -2120,6 +2121,29 @@ def alt_cmd(self) -> None:
     }
 
 
+def test_cli_app_async_method_no_existing_loop():
+    class Command(BaseSettings):
+        called: bool = False
+
+        async def cli_cmd(self) -> None:
+            self.called = True
+
+    assert CliApp.run(Command, cli_args=[]).called
+
+
+def test_cli_app_async_method_with_existing_loop():
+    class Command(BaseSettings):
+        called: bool = False
+
+        async def cli_cmd(self) -> None:
+            self.called = True
+
+    async def run_as_coro():
+        return CliApp.run(Command, cli_args=[])
+
+    assert asyncio.run(run_as_coro()).called
+
+
 def test_cli_app_exceptions():
     with pytest.raises(
         SettingsError, match='Error: NotPydanticModel is not subclass of BaseModel or pydantic.dataclasses.dataclass'