Create and manage temporary file used for unit tests. File is deleted on Drop
TestFile structure. Holds opened File and PathBuf. Files are created in temporary directory with unique names. Deleted on Drop. This structure can be dereferenced to &File and implements AsRef for Path, PathBuf and File.
Create test file with content supplied by initializer closure
Create an empty test file
Create a TestFile from string
Turns file into TestFile
Generate unique tmp file name