How can I remove my test submissions?

Would like to know how to remove submission request from the 'history'. I would only want to see valid submissions - not tests.

You can delete your test submissions from the SUBMISSIONS PAGE. However, be mindful that this process can not be undone. Here's a snippet from the complete guide I'm linking below:

When deleting submissions individually, you will see this warning message (see screenshot below). Please note that deleting submission data is irreversible and will permanently remove it in our servers, including the file uploads on them.

Complete guide: How-to-Delete-Form-Submission-Data 

So I strongly urge you to make a backup copy of your Submission Data just in case you'd still need them even if they were just tests.

There are plenty of ways to do that, feel free pick one that will work for you:

Related guides:

How-to-Export-All-of-Your-Data-at-Once

How-to-Download-Form-Submissions-as-Excel-CSV-PDF