Lambda function not taken into account in tests - python-3.x

Question

I am trying to deploy my first function on AWS Lambda that should store results on my S3 instance following this tutorial. To be sure I have the permission to write files to the S3 bucket I've created I added the code below the commented one into the Function code section.
# import json
# def lambda_handler(event, context):
# # TODO implement
# return {
# 'statusCode': 200,
# 'body': json.dumps('Hello from fucking Lambda!')
# }
import boto3
def lambda_handler(event, context):
s3 = boto3.resource("s3") # pointer to AWS S3 service
bucket_name = "my-own-bucket" # bucket for saving our data
file_name = "HelloWorld.txt" # dummy file
body = event['key1'] + ' ' + event['key2'] + event['key3']
# "Hello World!" from event input
s3.Bucket(bucket_name).put_object(Key=file_name, Body=body)
# write object to bucket
return f"Succeed! Find your new {file_name} file in {bucket_name} bucket ;)"
I used the template test event:
My code automatically saved, so I opened the S3 bucket again and verified that a HelloWorld.txt file existed. But it didn't. And the execution results were:
Response:
{
"statusCode": 200,
"body": "\"Hello from Lambda!\""
}
Request ID:
"93c1c61c-73cf-4308-9a88-0e8771612b8e"
Function logs:
START RequestId: 93c1c61c-73cf-4308-9a88-0e8771612b8e Version: $LATEST
END RequestId: 93c1c61c-73cf-4308-9a88-0e8771612b8e
REPORT RequestId: 93c1c61c-73cf-4308-9a88-0e8771612b8e Duration: 0.32 ms Billed Duration: 100 ms Memory Size: 128 MB Max Memory Used: 43 MB
Like if the commented code had still been taken into account.

Answer 1

It could be due to following reasons:
You are invoking old lambda version, rather then your latest version.
You are not deploying your changes. In the new UI, there is no 'Save' button. Instead there is orange Deploy button.