Add unit test

Author: kernc

backtesting/test/_test.py

@@ -506,6 +506,18 @@ def coroutine(self):
         stats = self._Backtest(coroutine).run()
         self.assertEqual(len(stats._trades), 1)
 
+    def test_order_tag(self):
+        def coroutine(self):
+            yield self.buy(size=2, tag=1)
+            yield self.sell(size=1, tag='s')
+            yield self.sell(size=1)
+
+            yield self.buy(tag=2)
+            yield self.position.close()
+
+        stats = self._Backtest(coroutine).run()
+        self.assertEqual(list(stats._trades.Tag), [1, 1, 2])
+
 
 class TestOptimize(TestCase):
     def test_optimize(self):