randomize was broken -- elements could not exchange with themselves

basis/random/random-tests.factor

@@ -1,5 +1,5 @@
 USING: random sequences tools.test kernel math math.functions
-sets ;
+sets grouping ;
 IN: random.tests
 
 [ 4 ] [ 4 random-bytes length ] unit-test
@@ -17,3 +17,6 @@ IN: random.tests
 [ t ] [ 1000 [ 400 random ] replicate prune length 256 > ] unit-test
 
 [ f ] [ 0 random ] unit-test
+
+[ f ]
+[ 100 [ { 0 1 } random ] replicate all-equal? ] unit-test

basis/random/random.factor

@@ -53,7 +53,7 @@ PRIVATE>
     ] if-empty ;
 
 : randomize ( seq -- seq' )
-    dup length 1 (a,b] [ dup random pick exchange ] each ;
+    dup length 1+ 2 (a,b] [ [ random ] [ 1- ] bi pick exchange ] each ;
 
 : delete-random ( seq -- elt )
     [ length random-integer ] keep [ nth ] 2keep delete-nth ;