add contracts and tests for isomorphism-compose and -thrush

unstable/lens/isomorphism/compound.rkt

@@ -1,10 +1,21 @@
 #lang sweet-exp racket/base
 
-provide isomorphism-compose
+require racket/contract/base
-        isomorphism-thrush
+provide
+  contract-out
+    isomorphism-compose
+      (rest-> isomorphism-lens? isomorphism-lens?)
+    isomorphism-thrush
+      (rest-> isomorphism-lens? isomorphism-lens?)
 
 require racket/match
+        lens/private/util/rest-contract
         "base.rkt"
+module+ test
+  require lens/private/base/main
+          lens/private/compound/identity
+          rackunit
+          "data.rkt"
 
 (define (isomorphism-compose . args)
   (match args
@@ -16,3 +27,7 @@ require racket/match
 (define (isomorphism-thrush . args)
   (apply isomorphism-compose (reverse args)))
 
+module+ test
+  (define string->vector-lens (isomorphism-thrush string->list-lens list->vector-lens))
+  (check-equal? (lens-view string->vector-lens "abc") #(#\a #\b #\c))
+  (check-equal? (lens-set string->vector-lens "abc" #(#\1 #\2 #\3)) "123")