Manual test
Navigate to Users > Accounts > Bulk user actions in site administration
Press Add all
Select With selected users: Download and press Go
Select from Export users as and press Download for each of the following formats (those using the Spout library)
Comma separated values (.csv)
Microsoft Excel (.xlsx)
OpenDocument (.ods)
Confirm each exported file is formatted appropriately according to it's type
Automated test
$ vendor/bin/phpunit --filter dataformat_testcase