diff --git a/intro-to-algorithms/ch01.py b/intro-to-algorithms/ch01.py
new file mode 100644
index 0000000..aced933
--- /dev/null
+++ b/intro-to-algorithms/ch01.py
@@ -0,0 +1,57 @@
+from __future__ import print_function
+
+import os
+import random
+import unittest
+
+
+DEBUG = os.environ.get('DEBUG') == '1'
+
+
+def debug(msg):
+    if DEBUG:
+        print(msg)
+
+
+def insertion_sort(arr):
+    debug('BEGIN')
+    for j in range(1, len(arr)):
+        key = arr[j]
+        i = j - 1
+        debug('FOR:\tj={}, key={}, i={}'.format(j, key, i))
+
+        while i > -1 and arr[i] > key:
+            arr[i + 1] = arr[i]
+            debug('WHILE:\tset: arr[{}] = {}'.format(i + 1, arr[i]))
+            i = i - 1
+
+        arr[i + 1] = key
+        debug('FOR:\tset: arr[{}] = {}'.format(i + 1, key))
+
+    debug('END')
+    return arr
+
+
+class TestStuff(unittest.TestCase):
+
+    def test_insertion_sort_small(self):
+        self.assertEqual(
+            [1, 2, 3, 4, 5, 6],
+            insertion_sort([5, 2, 4, 6, 1, 3])
+        )
+
+    def test_insertion_sort_large(self):
+        inlist = range(1000)
+        listcopy = inlist[:]
+        random.shuffle(inlist)
+        random.shuffle(inlist)
+        self.assertEqual(listcopy, insertion_sort(inlist))
+
+    def test_insertion_sort_large_reversed(self):
+        inlist = range(1000)
+        listcopy = inlist[:]
+        self.assertEqual(listcopy, insertion_sort(list(reversed(inlist))))
+
+
+if __name__ == '__main__':
+    unittest.main()