diff --git a/tests/test_algorithm.py b/tests/test_algorithm.py
index b922a88f..8d286bd1 100644
--- a/tests/test_algorithm.py
+++ b/tests/test_algorithm.py
@@ -30,7 +30,7 @@ from zipline.finance.trading import SimulationParameters
 
 class TestRecordAlgorithm(TestCase):
     def setUp(self):
-        self.sim_params = factory.create_simulation_parameters()
+        self.sim_params = factory.create_simulation_parameters(num_days=4)
         trade_history = factory.create_trade_history(
             133,
             [10.0, 10.0, 11.0, 11.0],
@@ -38,13 +38,15 @@ class TestRecordAlgorithm(TestCase):
             timedelta(days=1),
             self.sim_params
         )
+
         self.source = SpecificEquityTrades(event_list=trade_history)
         self.df_source, self.df = \
             factory.create_test_df_source(self.sim_params)
 
     def test_record_incr(self):
-        algo = RecordAlgorithm()
+        algo = RecordAlgorithm(sim_params=self.sim_params)
         output = algo.run(self.source)
+
         np.testing.assert_array_equal(output['incr'].values,
                                       range(1, len(output) + 1))
 
@@ -52,7 +54,7 @@ class TestRecordAlgorithm(TestCase):
 class TestTransformAlgorithm(TestCase):
     def setUp(self):
         setup_logger(self)
-        self.sim_params = factory.create_simulation_parameters()
+        self.sim_params = factory.create_simulation_parameters(num_days=4)
         setup_logger(self)
 
         trade_history = factory.create_trade_history(
@@ -109,7 +111,9 @@ class TestTransformAlgorithm(TestCase):
         assert isinstance(algo.sources[0], DataFrameSource)
 
     def test_panel_as_input(self):
-        algo = TestRegisterTransformAlgorithm(sids=[0, 1])
+        algo = TestRegisterTransformAlgorithm(
+            self.sim_params,
+            sids=[0, 1])
         algo.run(self.panel)
         assert isinstance(algo.sources[0], DataPanelSource)
 
diff --git a/zipline/utils/factory.py b/zipline/utils/factory.py
index af72c80b..e70d2eef 100644
--- a/zipline/utils/factory.py
+++ b/zipline/utils/factory.py
@@ -40,14 +40,20 @@ from zipline.sources.test_source import (
 
 
 def create_simulation_parameters(year=2006, start=None, end=None,
-                                 capital_base=float("1.0e5")
+                                 capital_base=float("1.0e5"),
+                                 num_days=None
                                  ):
     """Construct a complete environment with reasonable defaults"""
     if start is None:
         start = datetime(year, 1, 1, tzinfo=pytz.utc)
     if end is None:
-        end = datetime(year, 12, 31, tzinfo=pytz.utc)
-
+        if num_days:
+            trading.environment = trading.TradingEnvironment()
+            start_index = trading.environment.trading_days.searchsorted(
+                start)
+            end = trading.environment.trading_days[start_index + num_days - 1]
+        else:
+            end = datetime(year, 12, 31, tzinfo=pytz.utc)
     sim_params = SimulationParameters(
         period_start=start,
         period_end=end,