a second attempt to fix #203

Judging from the current code, at some point in the distant past, test cases
were run by rewrite the module body to insert a call that kicked off the test
cases. Get slightly closer to that world by moving the test case into the
main body of the dynamic-wind so that errors in either the testing or the module
body don't skip the call that initializes the REPL

htdp-lib/lang/run-teaching-program.rkt

@@ -85,13 +85,13 @@
        (dynamic-wind
         void
         (lambda ()
-          (dynamic-require ''#,module-name #f))  ;; work around a bug in dynamic-require
+          (dynamic-require ''#,module-name #f)   ;; work around a bug in dynamic-require
+          #,(if enable-testing?
+                #'(test)
+                #'(begin)))
         (lambda ()
           (unless done-already?
             (set! done-already? #t)
-            #,(if enable-testing?
-                  #'(test)
-                  #'(begin))
             (current-namespace (module->namespace ''#,module-name))))))))
 
 ;; take all of the body expressions from the port