make run the default action of a test in tester

tests/iter/titer_no_tuple_unpack.nim

@@ -1,3 +1,18 @@
+discard """
+output: '''
+3 4
+4 5
+5 6
+6 7
+7 8
+(x: 3, y: 4)
+(x: 4, y: 5)
+(x: 5, y: 6)
+(x: 6, y: 7)
+(x: 7, y: 8)
+'''
+"""
+
 
 iterator xrange(fromm, to: int, step = 1): tuple[x, y: int] =
   var a = fromm
@@ -10,4 +25,3 @@ for a, b in xrange(3, 7):
 
 for tup in xrange(3, 7):
   echo tup
-