Ensure that the file_directory_temp() function always returns a value.
function testFileDirectoryTemp() {
// Start with an empty variable to ensure we have a clean slate.
variable_set('file_temporary_path', '');
$tmp_directory = file_directory_temp();
$this
->assertEqual(empty($tmp_directory), FALSE, 'file_directory_temp() returned a non-empty value.');
$setting = variable_get('file_temporary_path', '');
$this
->assertEqual($setting, $tmp_directory, "The 'file_temporary_path' variable has the same value that file_directory_temp() returned.");
}