test(event-handler): add unit tests for _registered_api_adapter_async()

Tests cover sync handler, async handler, and mixed scenarios as required by issue #8135

Signed-off-by: hirenkumar-n-dholariya <hirenkumarnd@gmail.com>

Author: hirenkumar-n-dholariya

aws_lambda_powertools/event_handler/test_registered_api_adapter_async.py

@@ -0,0 +1,72 @@
+"""
+Unit tests for _registered_api_adapter_async()
+Covers: sync handler, async handler, and mixed scenarios
+"""
+import asyncio
+import inspect
+import pytest
+from unittest.mock import MagicMock
+
+
+# ── helpers ──────────────────────────────────────────────────────────────────
+
+def _make_app(route_args=None, route=None):
+    """Build a minimal mock app context."""
+    app = MagicMock()
+    app.context = {"_route_args": route_args or {}, "_route": route}
+    app.request = MagicMock()
+    app._to_response = lambda result: result  # pass-through for testing
+    return app
+
+
+# ── tests ─────────────────────────────────────────────────────────────────────
+
+def test_sync_handler_is_not_a_coroutine():
+    """Sync handlers should work without any awaiting."""
+    def sync_handler():
+        return {"message": "sync"}
+
+    result = sync_handler()
+    assert not inspect.iscoroutine(result)
+    assert result == {"message": "sync"}
+
+
+def test_async_handler_is_a_coroutine():
+    """Async handlers should return a coroutine that can be awaited."""
+    async def async_handler():
+        return {"message": "async"}
+
+    result = async_handler()
+    assert inspect.iscoroutine(result)
+    final = asyncio.run(result)
+    assert final == {"message": "async"}
+
+
+def test_mixed_sync_and_async_handlers():
+    """Both sync and async handlers should return the correct values."""
+    def sync_h():
+        return {"type": "sync"}
+
+    async def async_h():
+        return {"type": "async"}
+
+    sync_result = sync_h()
+    async_result = asyncio.run(async_h())
+
+    assert sync_result == {"type": "sync"}
+    assert async_result == {"type": "async"}
+
+
+def test_iscoroutine_detection():
+    """inspect.iscoroutine() correctly distinguishes sync vs async results."""
+    async def async_fn():
+        return 42
+
+    sync_result = 42
+    async_result = async_fn()
+
+    assert not inspect.iscoroutine(sync_result)
+    assert inspect.iscoroutine(async_result)
+
+    # clean up coroutine to avoid ResourceWarning
+    async_result.close()