You want to test an AWS Lambda function locally that will be triggered by an S3 object upload before deploying it to production. Which approach requires the least operational effort to achieve this?

The AWS Serverless Application Model (SAM) CLI offers robust local testing capabilities, making it the most efficient option here. sam local start-lambda creates a local endpoint, sam local generate-event s3 put quickly provides a realistic S3 event payload, and sam local invoke executes the function locally with that payload. This integrated workflow minimizes manual effort and accurately simulates the production environment. Using aws s3api put-object to trigger a local Lambda function isn't directly supported; S3 events trigger deployed Lambda functions. Manually creating a JSON file and using aws lambda invoke locally is possible but more cumbersome than SAM CLI, as you'd need to craft the event JSON yourself. The AWS Management Console is for testing deployed Lambda functions, not local ones.