Added tree depth first search challenge.

graphs_trees/tree_dfs/test_dfs.py

@@ -0,0 +1,57 @@
+from __future__ import print_function
+from nose.tools import assert_equal
+
+
+class TestDfs(object):
+
+    def test_dfs(self):
+        root = Node(5)
+        root.insert(2)
+        root.insert(8)
+        root.insert(1)
+        root.insert(3)
+
+        with captured_output() as (out, err):
+            root.in_order_traversal(sys.stdout.write)
+            assert_equal(out.getvalue().strip(), '12358')
+
+        with captured_output() as (out, err):
+            root.pre_order_traversal(sys.stdout.write)
+            assert_equal(out.getvalue().strip(), '52138')
+
+        with captured_output() as (out, err):
+            root.post_order_traversal(sys.stdout.write)
+            assert_equal(out.getvalue().strip(), '13285')
+
+        with captured_output() as (out, err):
+            root.bfs(sys.stdout.write)
+            assert_equal(out.getvalue().strip(), '52813')
+
+        root = Node(1)
+        root.insert(2)
+        root.insert(3)
+        root.insert(4)
+        root.insert(5)
+
+        with captured_output() as (out, err):
+            root.in_order_traversal(sys.stdout.write)
+            assert_equal(out.getvalue().strip(), '12345')
+
+        with captured_output() as (out, err):
+            root.pre_order_traversal(sys.stdout.write)
+            assert_equal(out.getvalue().strip(), '12345')
+
+        with captured_output() as (out, err):
+            root.post_order_traversal(sys.stdout.write)
+            assert_equal(out.getvalue().strip(), '54321')
+
+        print('Success: test_dfs')
+
+
+def main():
+    test = TestDfs()
+    test.test_dfs()
+
+
+if __name__ == '__main__':
+    main()