random: Add test_randrange.py.

random/test_randrange.py

@@ -0,0 +1,14 @@
+from random import *
+
+
+UPPER = 100
+
+s = set()
+
+# This number of course depends on a particular PRNG and its default seed
+# as used by MicroPython.
+for c in range(496):
+    r = randrange(UPPER)
+    s.add(r)
+
+assert len(s) == UPPER