Should test data be used in production?

Question

We are deploying an update to our main application in production. The update has been tested in QA and it looks good to go. Our client wants to do a test in production. For that case, we will run the application using "test data" in production and once the test has been finished, we will delete the "test data".

A couple of server admins are against this because "test data doesn't belong to production". I think it's OK since the QA server and the production server have different hardware and the databases house different applications (QA has more databases, production is dedicated). Besides that, are there other facts that I can use to back my opinion?

EDIT: adding context

The application is a tool that automates the reception and validation of data. We receive the files via email and this tool automatically validates them and imports them to the database. We have a BI system that creates reports using this information (excel files are received by email, then validate, then reports/views come out, all this automated).

The "test data" would be old files (good and bad files from previous efforts) that represent true data (actually it is true data but with problems or just too old).

Answer 1

Yes! But manual usage of test data in production does not sound like a good idea to me as it cannot be controlled or monitored. My answer below is assuming the test data is used for automated testing.

Test data in production is "todays" need. This was not a requirement back then when automated testing was not a requirement(or did not exist). So in general this will be frowned upon. Security is the main reason. Its impact in messing up site analytics is another reason. These are genuine and good reasons.

One cannot decide one day to simply put test data in production especially towards the end of project. This needs to be made a requirement from the time development starts. So the test data needs to be there in production from the very first deployment onwards. And its impact needs to studied and documented. Organization as a whole need to understand it's benefit and impact.

Test data needs to be divided based on it's type,need or context. eg: Retrievable test data and editable test data. First step would be to have Retrievable(read only-never changes) test data available. Perhaps this is farthest we could go in many case, still would provide good results. And creation of this read only test data needs to be automated and preferably documented.

The benefits of having test data in production is huge. An automated test of an application is more precious that then the application itself. If the management realizes that then at least the initial "frown" changes.I feel test data in production should be considered a requirement/userstory and all problems against it should be mitigated. And new patterns of development need to evolve in this area.

This discussion is also related to integration testing and this article focuses on the benefits of it over unit testing