diff --git a/ceam_tests/util.py b/ceam_tests/util.py
index <HASH>..<HASH> 100644
--- a/ceam_tests/util.py
+++ b/ceam_tests/util.py
@@ -25,8 +25,8 @@ def setup_simulation(components, population_size = 100, start=datetime(1990, 1, 
 
     return simulation
 
-def pump_simulation(simulation, duration=None, iterations=None):
-    timestep = config.getint('simulation_parameters', 'time_step')
+def pump_simulation(simulation, time_step_days=30.5, duration=None, iterations=None):
+    timestep = timedelta(days=time_step_days) 
     start_time = datetime(1990, 1, 1)
     simulation.current_time = start_time
     iteration_count = 0
added time step days arg to pump_simulation