When preparing to submit a new data feed, you should:
- Submit a test data feed
- Include all items in your inventory
- Submit multiple feeds to process everything at once
- Give all feeds the same name for consistency
The test data feed option allows you to debug your data feed by uploading it to Merchant Center without making these items available in the search results. With a test data feed, you can upload your data feed in order to check and fix feed errors as many times as you want. Once you are happy with the feed processing results, you can upload the same file as a normal feed.
Read more here: https://support.google.com/merchants/answer/1188998?hl=en