Minor edits and bug fixes.

lang/en/qtype_stack.php

@@ -380,7 +380,7 @@ $string['ATAlgEquiv_SA_not_matrix']     = 'Your answer should be a matrix, but i
 $string['ATAlgEquiv_SA_not_list']       = 'Your answer should be a list, but is not.  Note that the syntax to enter a list is to enclose the comma separated values with square brackets. ';
 $string['ATAlgEquiv_SA_not_set']        = 'Your answer should be a set, but is not.  Note that the syntax to enter a set is to enclose the comma separated values with curly brackets. ';
 $string['ATAlgEquiv_SA_not_equation']   = 'Your answer should be an equation, but is not. ';
-$string['ATAlgEquiv_TA_not_equation']   = 'Your answer is an equation, but the expression to which it is being compared is not.  You may have typed something like y=2 when you only needed to type 2. ';
+$string['ATAlgEquiv_TA_not_equation']   = 'Your answer is an equation, but the expression to which it is being compared is not.  You may have typed something like "y=2*x+1" when you only needed to type "2*x+1". ';
 $string['ATAlgEquiv_SA_not_inequality'] = 'Your answer should be an inequality, but is not. ';
 $string['Subst']                        = 'Your answer would be correct if you used the following substitution of variables. {$a->m0} ';
 

questiontestform.php

@@ -43,8 +43,8 @@ class qtype_stack_question_test_form extends moodleform {
         $mform->addElement('header', 'inputsheader', get_string('testinputs', 'qtype_stack'));
 
         foreach ($question->inputs as $inputname => $input) {
+            // We do not require these to be filled in, (or contain valid input), as the teacher may want to test such cases.
             $input->add_to_moodleform($mform);
-            $mform->addRule($inputname, get_string('required'), 'required', '', 'client');
         }
 
         // TODO I would really like to add a button here: