Index: Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/PipingFailureMechanismTest.cs
===================================================================
diff -u -rc0e407c65daebe4f446f9414367593eff80af1b2 -red0b4ea830beb801bcc0e3eb5b28993001ed2981
--- Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/PipingFailureMechanismTest.cs	(.../PipingFailureMechanismTest.cs)	(revision c0e407c65daebe4f446f9414367593eff80af1b2)
+++ Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/PipingFailureMechanismTest.cs	(.../PipingFailureMechanismTest.cs)	(revision ed0b4ea830beb801bcc0e3eb5b28993001ed2981)
@@ -1,4 +1,6 @@
-using Core.Common.Base;
+using System.Collections.Generic;
+
+using Core.Common.Base;
 using NUnit.Framework;
 using Rhino.Mocks;
 
@@ -127,5 +129,67 @@
             // Call & Assert
             pipingFailureMechanism.Detach(observer);
         }
+
+        [Test]
+        public void Calculations_AddPipingCalculation_ItemIsAddedToCollection()
+        {
+            // Setup
+            var calculation = new PipingCalculation();
+
+            var failureMechanism = new PipingFailureMechanism();
+
+            // Call
+            failureMechanism.Calculations.Add(calculation);
+
+            // Assert
+            CollectionAssert.Contains(failureMechanism.Calculations, calculation);
+        }
+
+        [Test]
+        public void Calculations_RemovePipingCalculation_ItemIsRemovedFromCollection()
+        {
+            // Setup
+            var calculation = new PipingCalculation();
+
+            var failureMechanism = new PipingFailureMechanism();
+            failureMechanism.Calculations.Add(calculation);
+
+            // Call
+            failureMechanism.Calculations.Remove(calculation);
+
+            // Assert
+            CollectionAssert.DoesNotContain(failureMechanism.Calculations, calculation);
+        }
+
+        [Test]
+        public void Calculations_AddPipingCalculationFolder_ItemIsAddedToCollection()
+        {
+            // Setup
+            var folder = new PipingCalculationGroup();
+
+            var failureMechanism = new PipingFailureMechanism();
+
+            // Call
+            failureMechanism.Calculations.Add(folder);
+
+            // Assert
+            CollectionAssert.Contains(failureMechanism.Calculations, folder);
+        }
+
+        [Test]
+        public void Calculations_RemovePipingCalculationFolder_ItemIsRemovedFromCollection()
+        {
+            // Setup
+            var folder = new PipingCalculationGroup();
+
+            var failureMechanism = new PipingFailureMechanism();
+            failureMechanism.Calculations.Add(folder);
+
+            // Call
+            failureMechanism.Calculations.Remove(folder);
+
+            // Assert
+            CollectionAssert.DoesNotContain(failureMechanism.Calculations, folder);
+        }
     }
 }
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