private string _ReadFromTestSubject()
 {
     using (var testSubject = new CachedFile(_backingFile))
     {
         return testSubject.Contents;
     }
 }
 private void _WriteToTestSubject(string valueWritten)
 {
     using (var testSubject = new CachedFile(_backingFile, requireToExistAlready: null))
     {
         testSubject.Contents = valueWritten;
     }
 }