
The "item.rkt" test (use `require') creates a frame to select among
several types of control-testing frames. Click the `Get Instructions'
button in the top-left for more information.

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The "mem.rkt" test
  gracket mem.rkt
creates a lot of frames and instance of other objects, reporting
memory information along the way. At the end, before the last memory
dump, objects that are still allocated are displayed like this:
  (frame (1 . 5))
This means that the frame allocated by thread #1 at cycle 5
(counting down from some number) hasn't been garbage-collected.
If there's a few of these lines (around 10), that's ok.
A large number of lines (say, 50) indicates a GC problem.
