@@ -21,7 +21,7 @@ danger.gif           words.txt	      color_list.py        structshape.py
 
 TESTS = Gui_test.py     Lumpy_test.py    	TurmiteWorld_test.py \
 AmoebaWorld_test.py  	World_test.py		TurtleWorld_test.py  \
-Sync_test.py		CellWorld_test.py
+Sync_test.py		CellWorld_test.py       structshape_test.py
 
 SCRIPTS = lumpy_example1.py  lumpy_example2.py  lumpy_example3.py      \
 
 
@@ -13,8 +13,12 @@
 """
 
 def structshape(ds):
-    """Returns a string that describes the shape of the given
-    data structure."""
+    """Returns a string that describes the shape of a data structure.
+
+    ds: any Python object
+
+    Returns: string
+    """
     typename = type(ds).__name__
 
     # handle sequences
@@ -46,7 +50,12 @@ def structshape(ds):
 
 
 def listrep(t):
-    """return a string representation of a list of type strings"""
+    """Returns a string representation of a list of type strings.
+
+    t: list of strings
+
+    Returns: string
+    """
     current = t[0]
     count = 0
     res = []
@@ -60,19 +69,33 @@ def listrep(t):
     append(res, current, count)
     return setrep(res)
 
+
 def setrep(s):
-    """return a string representation of a set of type strings"""
+    """Returns a string representation of a set of type strings.
+
+    s: set of strings
+
+    Returns: string
+    """
     rep = ', '.join(s)
     if len(s) == 1:
         return rep
     else:
         return '(' + rep + ')'
     return 
 
+
 def append(res, typestr, count):
-    """res is a list of type strings; this function adds a new
-    type string that represent (count) instances of type string
-    (typestr)"""
+    """Adds a new element to a list of type strings.
+
+    Modifies res.
+
+    res: list of type strings
+    typestr: the new type string
+    count: how many of the new type there are
+
+    Returns: None
+    """
     if count == 1:
         rep = typestr
     else:
 
@@ -0,0 +1,44 @@
+"""This module is part of Swampy, a suite of programs available from
+allendowney.com/swampy.
+
+Copyright 2011 Allen B. Downey
+Distributed under the GNU General Public License at gnu.org/licenses/gpl.html.
+"""
+
+import unittest
+
+from structshape import structshape
+
+class Tests(unittest.TestCase):
+
+    def test_lumpy(self):
+        t = [1,2,3]
+        self.assertEqual(structshape(t), 'list of 3 int')
+
+        t2 = [[1,2], [3,4], [5,6]]
+        self.assertEqual(structshape(t2), 'list of 3 list of 2 int')
+
+        t3 = [1, 2, 3, 4.0, '5', '6', [7], [8], 9]
+        self.assertEqual(structshape(t3), 'list of (3 int, float, 2 str, 2 list of int, int)')
+
+        class Point:
+            """trivial object type"""
+
+        t4 = [Point(), Point()]
+        self.assertEqual(structshape(t4), 'list of 2 Point')
+
+        s = set('abc')
+        self.assertEqual(structshape(s), 'set of 3 str')
+
+        lt = zip(t, s)
+        self.assertEqual(structshape(lt), 'list of 3 tuple of (int, str)')
+
+        d = dict(lt)        
+        self.assertEqual(structshape(d), 'dict of 3 int->str')
+
+        it = iter('abc')
+        self.assertEqual(structshape(it), 'iterator of 3 str')
+
+
+if __name__ == '__main__':
+    unittest.main()