Added two POW test cases. The last one is still failing\!

tests/test_line.py

@@ -39,3 +39,16 @@ class TestLine(unittest.TestCase):
         l0, l1, l2 = Leaf(1), Leaf(2), Leaf(3)
         plus = Node('+', l0, l1, l2)
         self.assertEquals(generate_line(plus), '1 + 2 + 3')
+
+    def test_pow_basic(self):
+        a, b, c = Leaf('a'), Leaf('b'), Leaf('c')
+        node_pow = Node('^', a, Node('+', b, c))
+        self.assertEquals(generate_line(node_pow), 'a ^ (b + c)')
+
+    def test_pow_intermediate(self):
+        a, b, c, d, e = Leaf('a'), Leaf('b'), Leaf('c'), Leaf('d'), Leaf('e')
+        node_bc = Node('+', b, c)
+        node_de = Node('+', d, e)
+        node_mul = Node('*', a, node_bc)
+        node_pow = Node('^', node_mul, node_de)
+        self.assertEquals(generate_line(node_pow), 'a * (b + c) ^ (d + e)')