Unit tests in place and all tests passed.

lang/en/qtype_stack.php

locallib.php

stack/cas/cassession.class.php

stack/cas/casstring.class.php

stack/cas/castext.class.php

stack/cas/cliconnector.class.php

stack/cas/keyval.class.php

stack/cas/simpletest/test.cassession.class.php

stack/cas/simpletest/test.casstring.class.php

stack/cas/simpletest/test.castext.class.php

stack/cas/simpletest/test.keyval.class.php

stack/options.class.php

stack/test.php