Index: Ringtoets/Common/test/Ringtoets.Common.Service.Test/DesignWaterLevelCalculationActivityTest.cs
===================================================================
diff -u -rb341b132f7007d3f007d19872c0970292edd0d63 -r96a6ad152dc45508f0501e489c29611244e9d76c
--- Ringtoets/Common/test/Ringtoets.Common.Service.Test/DesignWaterLevelCalculationActivityTest.cs	(.../DesignWaterLevelCalculationActivityTest.cs)	(revision b341b132f7007d3f007d19872c0970292edd0d63)
+++ Ringtoets/Common/test/Ringtoets.Common.Service.Test/DesignWaterLevelCalculationActivityTest.cs	(.../DesignWaterLevelCalculationActivityTest.cs)	(revision 96a6ad152dc45508f0501e489c29611244e9d76c)
@@ -222,7 +222,7 @@
                     CalculationServiceTestHelper.AssertCalculationEndMessage(calculationName, messages[4]);
                 });
 
-                AssessmentLevelCalculationInput designWaterLevelCalculationInput = calculator.ReceivedInputs.First();
+                AssessmentLevelCalculationInput designWaterLevelCalculationInput = calculator.ReceivedInputs.Single();
 
                 Assert.AreEqual(hydraulicBoundaryLocation.Id, designWaterLevelCalculationInput.HydraulicBoundaryLocationId);
                 Assert.AreEqual(StatisticsConverter.ProbabilityToReliability(norm), designWaterLevelCalculationInput.Beta);