adding test to make sure every second and third line on a blank pad is empty

test_onetimepad.py

@@ -15,4 +15,16 @@ class TestOneTimePad(unittest.TestCase):
     def test_creates_pad_of_desired_length(self):
         for width in (72, 33, 99, 111):
             pad = OT.create_pad(2000, width=width)
-            self.assertEqual(2000, len((''.join(pad.split())).strip('.')))
+            lines = [line.strip('.') for line in pad.split('\n\n\n')]
+            self.assertEqual(2000, len(''.join(lines)))
+
+    def test_two_out_of_every_three_lines_are_empty_on_new_pad(self):
+        pad = OT.create_pad(2000)
+        for i, line in enumerate(pad.splitlines()):
+            lineno = i + 3
+            if not lineno % 3:
+                self.assertTrue(bool(len(line)),
+                                'line {0} is non-empty'.format(lineno))
+            else:
+                self.assertFalse(bool(len(line)),
+                                 'line {0} is empty'.format(lineno))