added commentary tags to WritingUnitTests

Author: campbelle2

pretext/UnitTesting/WritingUnitTests.ptx

@@ -163,28 +163,29 @@ assert grade(85) == 'B'
 assert grade(69) == 'F'
         </input></program>
 
-    
-                    <!--.. reveal:: ac_grade_unittest_aux_reveal-->
-                    <!--:instructoronly:-->
-                    <!--.. actex:: ac_grade_unittest_aux-->
-                    <!--testA = False-->
-                    <!--testB = False-->
-                    <!--testF = False-->
-                    <!--illegal = False-->
-                    <!--def grade(score):-->
-                    <!--global illegal, testA, testB, testF-->
-                    <!--if score > 100 or score < 0:-->
-                    <!--illegal = True-->
-                    <!--return ''-->
-                    <!--elif score >= 90:-->
-                    <!--testA = True-->
-                    <!--return 'A'-->
-                    <!--elif score >= 80:-->
-                    <!--testB = True-->
-                    <!--return 'B'-->
-                    <!--else:-->
-                    <!--testF = True-->
-                    <!--return 'F'-->
+                  <commentary>
+                    ac_grade_unittest_aux_reveal
+                    instructoronly
+                    actex:: ac_grade_unittest_aux
+                    testA = False
+                    testB = False
+                    testF = False
+                    illegal = False
+                    def grade(score):
+                    global illegal, testA, testB, testF
+                    if score > 100 or score < 0:
+                    illegal = True
+                    return ''
+                    elif score >= 90:
+                    testA = True
+                    return 'A'
+                    elif score >= 80:
+                    testB = True
+                    return 'B'
+                    else:
+                    testF = True
+                    return 'F'
+                    </commentary>
                 </solution>
     </exercise>
   </subsection>