** reorganize test directory

test/README.md

@@ -3,9 +3,8 @@ test
 
 Root directory for `trivial` package test cases.
 
-Each folder here contains 2 important files:
-- `pass.rkt` : driver for tests exercising intended behavior
-- `fail.rkt` : driver for tests that should raise type errors
+There should be 2 files for each module `M` in the parent directory.
+- `M-pass.rkt` : tests exercising intended behavior
+- `M-fail.rkt` : tests that should raise type errors
 
-Run either of these to see a few pass/fail tests.
-The scripts `all-X.rkt` in this folder run passing/failing tests.
+Run tests for any file with `raco test FILE.rkt`.