test.py

@pytest.mark.asyncio
async def test_resolver_async():
    # GIVEN
    app = AppSyncResolver()

    mock_event = {"typeName": "Customer", "fieldName": "field", "arguments": {}}

    # Note: this function would be defined in another module in an actual serverless application, and imported. 
    # Its structured this way here as we're testing the framework itself.
    @app.resolver(field_name="field")
    async def get_async():
        await asyncio.sleep(0.0001)
        return "value"

    # WHEN
    mock_context = LambdaContext()
    result = await app.resolve(mock_event, mock_context)

    # THEN
    assert result == "value"