scribble: add tests for traverse-element' and traverse-block'

original commit: d2ec0bf5cc259538bbad06752f65fe92dd885ff6

pkgs/racket-pkgs/racket-test/tests/scribble/docs/traverse.scrbl

@@ -0,0 +1,41 @@
+#lang scribble/base
+@(require scribble/core)
+
+@(traverse-element
+  (lambda (get set)
+   ;; Not delayed, and so result is "not ready, yet"
+   (get 'glossary "not ready, yet")))
+
+@(traverse-element
+  (lambda (get set)
+   ;; Delayed until second traversal:
+   (lambda (get set)
+    (get 'glossary "BROKEN"))))
+
+@; Same thing, but with blocks:
+
+@(traverse-block
+  (lambda (get set)
+    ;; Not delayed:
+    (para "The glossary is " 
+          (get 'glossary "not ready, yet"))))
+
+@(traverse-block
+  (lambda (get set)
+    ;; Delayed:
+    (lambda (get set)
+      (para "The glossary is " 
+            (get 'glossary "BROKEN")))))
+
+@(traverse-block
+  (lambda (get set)
+    ;; Adding a `delayed-block' doesn't delay:
+    (traverse-block
+      (lambda (get set)
+        (para "The glossary is "
+              (get 'glossary "not ready, yet"))))))
+
+@(traverse-block
+  (lambda (get set)
+    (set 'glossary "ready")
+    (para "Here is the glossary.")))

pkgs/racket-pkgs/racket-test/tests/scribble/docs/traverse.txt

@@ -0,0 +1,11 @@
+not ready, yet
+
+ready
+
+The glossary is not ready, yet
+
+The glossary is ready
+
+The glossary is not ready, yet
+
+Here is the glossary.