* CleanUp removes all files in our test registry and calls `t.Error` if something goes wrong. */

* Exists returns true if the file exists. Calls t.Error if something goes wrong while checking. */

* FileSays returns true if the file at the path contains the expected byte array content. */

* TmpDir Creates a tmp directory for us to use. */

* TmpFile Creates a tmp file for us to use when testing */

* DirContains returns true if the dir contains the path. Calls t.Error if something goes wrong while checking. */

* File Creates a specified file for us to use when testing */