Python: Make code testable

Avoid executing code on module level as this prevents importing the
module for testing. Especially infinite loops are evil.

90_Tower/python/test_tower.py

@@ -0,0 +1,49 @@
+import unittest
+
+import tower
+
+
+class TowerTestCase(unittest.TestCase):
+    def test_something(self):
+        t = tower.Tower()
+        self.assertTrue(t.empty())
+
+        d = tower.Disk(3)
+        t.add(d)
+        self.assertFalse(t.empty())
+
+        d5 = tower.Disk(5)
+        self.assertRaises(Exception, t.add, d5)
+        self.assertFalse(t.empty())
+
+    def test_oksize(self):
+        t = tower.Tower()
+        self.assertTrue(t.empty())
+
+        d5 = tower.Disk(5)
+        t.add(d5)
+        self.assertFalse(t.empty())
+
+        d3 = tower.Disk(3)
+        t.add(d3)
+        self.assertFalse(t.empty())
+
+        self.assertEqual(t.top(), d3)
+        self.assertEqual(t.pop(), d3)
+        self.assertEqual(t.pop(), d5)
+
+    def test_game(self):
+        g = tower.Game()
+        self.assertEqual(g.moves(), 0)
+        self.assertFalse(g.winner())
+
+    def test_format(self):
+        t = tower.Tower()
+        d3 = tower.Disk(3)
+        d5 = tower.Disk(5)
+        t.add(d5)
+        t.add(d3)
+
+
+if __name__ == "__main__":
+    unittest.main()