Prepare migrating testing auxiliary functions from tests
to testutil.
Remove local duplicates on testutil.WriteToNewTempFile().
Always favor testutil.NewTestCaseDir() over ioutil.TempDir().
Add test cases for the testing auxiliary functions.
* lint: various linting fixs
Signed-off-by: Marko Baricevic <marbar3778@yahoo.com>
* more linting
* more linting fixes
* more errchecking
* comment out errcheck for now
* undo error check
* address some comments
* remore require error
* change delete to batch delete
Co-authored-by: Alexander Bezobchuk <alexanderbez@users.noreply.github.com>