diff --git a/tests/test_algorithm.py b/tests/test_algorithm.py
index c93ea308..bc89e5f9 100644
--- a/tests/test_algorithm.py
+++ b/tests/test_algorithm.py
@@ -1081,10 +1081,10 @@ class TestBeforeTradingStart(TestCase):
             cls.trading_days[-1], 2, 50
         )
 
-        cls.minute_reader = BcolzMinuteBarReader(cls.tempdir.path)
-        cls.adj_reader = cls.create_adjustments_reader()
+        minute_reader = BcolzMinuteBarReader(cls.tempdir.path)
+        adj_reader = cls.create_adjustments_reader()
 
-        cls.daily_path = cls.tempdir.getpath("testdaily.bcolz")
+        daily_path = cls.tempdir.getpath("testdaily.bcolz")
         dfs = {
             1: create_daily_df_for_asset(cls.env, cls.trading_days[0],
                                          cls.trading_days[-1]),
@@ -1094,7 +1094,7 @@ class TestBeforeTradingStart(TestCase):
                                          cls.trading_days[-1])
         }
         daily_writer = DailyBarWriterFromDataFrames(dfs)
-        daily_writer.write(cls.daily_path, cls.trading_days, dfs)
+        daily_writer.write(daily_path, cls.trading_days, dfs)
 
         cls.sim_params = SimulationParameters(
             period_start=cls.trading_days[1],
@@ -1105,9 +1105,9 @@ class TestBeforeTradingStart(TestCase):
 
         cls.data_portal = DataPortal(
             env=cls.env,
-            equity_daily_reader=BcolzDailyBarReader(cls.daily_path),
-            equity_minute_reader=cls.minute_reader,
-            adjustment_reader=cls.adj_reader
+            equity_daily_reader=BcolzDailyBarReader(daily_path),
+            equity_minute_reader=minute_reader,
+            adjustment_reader=adj_reader
         )
 
     @classmethod
@@ -1147,6 +1147,8 @@ class TestBeforeTradingStart(TestCase):
 
     @classmethod
     def tearDownClass(cls):
+        del cls.data_portal
+        del cls.env
         cls.tempdir.cleanup()
 
     def test_data_in_bts_minute(self):
@@ -1478,6 +1480,7 @@ class TestAlgoScript(TestCase):
 
     @classmethod
     def tearDownClass(cls):
+        del cls.data_portal
         del cls.env
         cls.tempdir.cleanup()
         teardown_logger(cls)
@@ -1867,6 +1870,7 @@ class TestGetDatetime(TestCase):
 
     @classmethod
     def tearDownClass(cls):
+        del cls.data_portal
         del cls.env
         teardown_logger(cls)
         cls.tempdir.cleanup()
@@ -1946,6 +1950,7 @@ class TestTradingControls(TestCase):
 
     @classmethod
     def tearDownClass(cls):
+        del cls.data_portal
         del cls.env
         cls.tempdir.cleanup()
 
@@ -2362,6 +2367,7 @@ class TestAccountControls(TestCase):
 
     @classmethod
     def tearDownClass(cls):
+        del cls.data_portal
         del cls.env
         cls.tempdir.cleanup()
 
@@ -2529,6 +2535,7 @@ class TestFutureFlip(TestCase):
 
     @classmethod
     def tearDownClass(cls):
+        del cls.data_portal
         cls.tempdir.cleanup()
 
     @skip
@@ -2648,6 +2655,7 @@ class TestOrderCancelation(TestCase):
 
     @classmethod
     def tearDownClass(cls):
+        del cls.data_portal
         cls.tempdir.cleanup()
 
     @classmethod
diff --git a/tests/test_api_shim.py b/tests/test_api_shim.py
index 594a0a5a..b04fb09d 100644
--- a/tests/test_api_shim.py
+++ b/tests/test_api_shim.py
@@ -164,6 +164,11 @@ class TestAPIShim(TestCase):
             env=cls.env
         )
 
+    @classmethod
+    def tearDownClass(cls):
+        del cls.adj_reader
+        cls.tempdir.cleanup()
+
     @classmethod
     def build_daily_data(cls):
         path = cls.tempdir.getpath("testdaily.bcolz")
@@ -217,10 +222,6 @@ class TestAPIShim(TestCase):
 
         return SQLiteAdjustmentReader(path)
 
-    @classmethod
-    def tearDownClass(cls):
-        cls.tempdir.cleanup()
-
     def setUp(self):
         self.data_portal = DataPortal(
             self.env,
@@ -229,6 +230,9 @@ class TestAPIShim(TestCase):
             adjustment_reader=self.adj_reader
         )
 
+    def tearDown(self):
+        del self.data_portal
+
     @classmethod
     def create_algo(cls, code, filename=None, sim_params=None):
         if sim_params is None:
diff --git a/tests/test_bar_data.py b/tests/test_bar_data.py
index bec4d34b..08ae9fdb 100644
--- a/tests/test_bar_data.py
+++ b/tests/test_bar_data.py
@@ -131,6 +131,8 @@ class TestMinuteBarData(TestBarDataBase):
 
     @classmethod
     def tearDownClass(cls):
+        del cls.data_portal
+        del cls.adjustments_reader
         cls.tempdir.cleanup()
 
     @classmethod
@@ -564,6 +566,8 @@ class TestDailyBarData(TestBarDataBase):
 
     @classmethod
     def tearDownClass(cls):
+        del cls.data_portal
+        del cls.adjustments_reader
         cls.tempdir.cleanup()
 
     @classmethod
diff --git a/tests/test_benchmark.py b/tests/test_benchmark.py
index a0f6757b..2b2960f4 100644
--- a/tests/test_benchmark.py
+++ b/tests/test_benchmark.py
@@ -100,6 +100,7 @@ class TestBenchmark(TestCase):
 
     @classmethod
     def tearDownClass(cls):
+        del cls.data_portal
         del cls.env
         cls.tempdir.cleanup()
 
diff --git a/tests/test_history.py b/tests/test_history.py
index b205e34a..bb59ee03 100644
--- a/tests/test_history.py
+++ b/tests/test_history.py
@@ -108,11 +108,18 @@ class HistoryTestCaseBase(TestCase):
 
         cls.create_data()
 
+    @classmethod
+    def tearDownClass(cls):
+        del cls.adj_reader
+        cls.tempdir.cleanup()
+
     def setUp(self):
         self.create_data_portal()
 
-    @classmethod
-    def create_data_portal(cls):
+    def tearDown(self):
+        del self.data_portal
+
+    def create_data_portal(self):
         raise NotImplementedError()
 
     @classmethod
@@ -169,10 +176,6 @@ class HistoryTestCaseBase(TestCase):
             }
         })
 
-    @classmethod
-    def tearDownClass(cls):
-        cls.tempdir.cleanup()
-
     @classmethod
     def create_adjustments_reader(cls):
         path = cls.tempdir.getpath("test_adjustments.db")
@@ -470,12 +473,11 @@ MINUTE_FIELD_INFO = {
 
 
 class MinuteEquityHistoryTestCase(HistoryTestCaseBase):
-    @classmethod
-    def create_data_portal(cls):
-        cls.data_portal = DataPortal(
-            cls.env,
-            equity_minute_reader=BcolzMinuteBarReader(cls.tempdir.path),
-            adjustment_reader=cls.adj_reader
+    def create_data_portal(self):
+        self.data_portal = DataPortal(
+            self.env,
+            equity_minute_reader=BcolzMinuteBarReader(self.tempdir.path),
+            adjustment_reader=self.adj_reader
         )
 
     @classmethod
@@ -1016,15 +1018,14 @@ class MinuteEquityHistoryTestCase(HistoryTestCaseBase):
 
 
 class DailyEquityHistoryTestCase(HistoryTestCaseBase):
-    @classmethod
-    def create_data_portal(cls):
-        daily_path = cls.tempdir.getpath("testdaily.bcolz")
+    def create_data_portal(self):
+        daily_path = self.tempdir.getpath("testdaily.bcolz")
 
-        cls.data_portal = DataPortal(
-            cls.env,
+        self.data_portal = DataPortal(
+            self.env,
             equity_daily_reader=BcolzDailyBarReader(daily_path),
-            equity_minute_reader=BcolzMinuteBarReader(cls.tempdir.path),
-            adjustment_reader=cls.adj_reader
+            equity_minute_reader=BcolzMinuteBarReader(self.tempdir.path),
+            adjustment_reader=self.adj_reader
         )
 
     @classmethod