Index: Ringtoets/MacroStabilityInwards/src/Ringtoets.MacroStabilityInwards.Forms/PresentationObjects/MacroStabilityInwardsCalculationGroupContext.cs
===================================================================
diff -u -r7691617baab138d49ebe8a6348f9897582027d6b -rd7de1609fbc7dd752e9d590f9a6637830df06232
--- Ringtoets/MacroStabilityInwards/src/Ringtoets.MacroStabilityInwards.Forms/PresentationObjects/MacroStabilityInwardsCalculationGroupContext.cs	(.../MacroStabilityInwardsCalculationGroupContext.cs)	(revision 7691617baab138d49ebe8a6348f9897582027d6b)
+++ Ringtoets/MacroStabilityInwards/src/Ringtoets.MacroStabilityInwards.Forms/PresentationObjects/MacroStabilityInwardsCalculationGroupContext.cs	(.../MacroStabilityInwardsCalculationGroupContext.cs)	(revision d7de1609fbc7dd752e9d590f9a6637830df06232)
@@ -75,7 +75,7 @@
 
         public override int GetHashCode()
         {
-            return base.GetHashCode() ^ Parent.GetHashCode();
+            return base.GetHashCode() ^ Parent?.GetHashCode() ?? 0;
         }
     }
 }
\ No newline at end of file
Index: Ringtoets/MacroStabilityInwards/test/Ringtoets.MacroStabilityInwards.Forms.Test/PresentationObjects/MacroStabilityInwardsCalculationGroupContextTest.cs
===================================================================
diff -u -ra1abe798a3991d9fff01eae522ccae2a43d0a931 -rd7de1609fbc7dd752e9d590f9a6637830df06232
--- Ringtoets/MacroStabilityInwards/test/Ringtoets.MacroStabilityInwards.Forms.Test/PresentationObjects/MacroStabilityInwardsCalculationGroupContextTest.cs	(.../MacroStabilityInwardsCalculationGroupContextTest.cs)	(revision a1abe798a3991d9fff01eae522ccae2a43d0a931)
+++ Ringtoets/MacroStabilityInwards/test/Ringtoets.MacroStabilityInwards.Forms.Test/PresentationObjects/MacroStabilityInwardsCalculationGroupContextTest.cs	(.../MacroStabilityInwardsCalculationGroupContextTest.cs)	(revision d7de1609fbc7dd752e9d590f9a6637830df06232)
@@ -40,7 +40,7 @@
         [Test]
         [TestCase(true)]
         [TestCase(false)]
-        public void ParameteredConstructor_ExpectedValues(bool withParent)
+        public void ParameteredConstructor_ExpectedValues(bool hasParent)
         {
             // Setup
             var mocks = new MockRepository();
@@ -57,7 +57,7 @@
                 MacroStabilityInwardsStochasticSoilModelTestFactory.CreateValidStochasticSoilModel()
             };
 
-            CalculationGroup parent = withParent ? new CalculationGroup() : null;
+            CalculationGroup parent = hasParent ? new CalculationGroup() : null;
 
             var failureMechanism = new MacroStabilityInwardsFailureMechanism();
 
@@ -81,7 +81,8 @@
             mocks.VerifyAll();
         }
 
-        [TestFixture]
+        [TestFixture(true)]
+        [TestFixture(false)]
         private class MacroStabilityInwardsCalculationGroupContextEqualsTest
             : EqualsTestFixture<MacroStabilityInwardsCalculationGroupContext, DerivedMacroStabilityInwardsCalculationGroupContext>
         {
@@ -91,9 +92,10 @@
             private static readonly IEnumerable<MacroStabilityInwardsSurfaceLine> surfaceLines = new MacroStabilityInwardsSurfaceLine[0];
             private static readonly IEnumerable<MacroStabilityInwardsStochasticSoilModel> stochasticSoilModels = new MacroStabilityInwardsStochasticSoilModel[0];
             private static readonly MacroStabilityInwardsFailureMechanism failureMechanism = new MacroStabilityInwardsFailureMechanism();
-            private static readonly CalculationGroup parent = new CalculationGroup();
             private static readonly CalculationGroup calculationGroup = new CalculationGroup();
 
+            private static CalculationGroup parent;
+
             [SetUp]
             public void SetUp()
             {
@@ -106,6 +108,11 @@
                 mocks.VerifyAll();
             }
 
+            public MacroStabilityInwardsCalculationGroupContextEqualsTest(bool hasParent)
+            {
+                parent = hasParent ? new CalculationGroup() : null;
+            }
+
             protected override MacroStabilityInwardsCalculationGroupContext CreateObject()
             {
                 return new MacroStabilityInwardsCalculationGroupContext(calculationGroup,
Index: Ringtoets/Piping/src/Ringtoets.Piping.Forms/PresentationObjects/PipingCalculationGroupContext.cs
===================================================================
diff -u -r3ddd2dfb07fb310dd90d5aac12e213d188c87a9a -rd7de1609fbc7dd752e9d590f9a6637830df06232
--- Ringtoets/Piping/src/Ringtoets.Piping.Forms/PresentationObjects/PipingCalculationGroupContext.cs	(.../PipingCalculationGroupContext.cs)	(revision 3ddd2dfb07fb310dd90d5aac12e213d188c87a9a)
+++ Ringtoets/Piping/src/Ringtoets.Piping.Forms/PresentationObjects/PipingCalculationGroupContext.cs	(.../PipingCalculationGroupContext.cs)	(revision d7de1609fbc7dd752e9d590f9a6637830df06232)
@@ -75,7 +75,7 @@
 
         public override int GetHashCode()
         {
-            return base.GetHashCode() ^ Parent.GetHashCode();
+            return base.GetHashCode() ^ Parent?.GetHashCode() ?? 0;
         }
     }
 }
\ No newline at end of file
Index: Ringtoets/Piping/test/Ringtoets.Piping.Forms.Test/PresentationObjects/PipingCalculationGroupContextTest.cs
===================================================================
diff -u -ra1abe798a3991d9fff01eae522ccae2a43d0a931 -rd7de1609fbc7dd752e9d590f9a6637830df06232
--- Ringtoets/Piping/test/Ringtoets.Piping.Forms.Test/PresentationObjects/PipingCalculationGroupContextTest.cs	(.../PipingCalculationGroupContextTest.cs)	(revision a1abe798a3991d9fff01eae522ccae2a43d0a931)
+++ Ringtoets/Piping/test/Ringtoets.Piping.Forms.Test/PresentationObjects/PipingCalculationGroupContextTest.cs	(.../PipingCalculationGroupContextTest.cs)	(revision d7de1609fbc7dd752e9d590f9a6637830df06232)
@@ -40,7 +40,7 @@
         [Test]
         [TestCase(true)]
         [TestCase(false)]
-        public void ParameteredConstructor_ExpectedValues(bool withParent)
+        public void ParameteredConstructor_ExpectedValues(bool hasParent)
         {
             // Setup
             var mocks = new MockRepository();
@@ -57,7 +57,7 @@
                 PipingStochasticSoilModelTestFactory.CreatePipingStochasticSoilModel()
             };
 
-            CalculationGroup parent = withParent ? new CalculationGroup() : null;
+            CalculationGroup parent = hasParent ? new CalculationGroup() : null;
 
             var failureMechanism = new PipingFailureMechanism();
 
@@ -76,34 +76,8 @@
             mocks.VerifyAll();
         }
 
-        [Test]
-        public void Equals_ToNull_ReturnFalse()
-        {
-            // Setup
-            var mocks = new MockRepository();
-            var assessmentSection = mocks.Stub<IAssessmentSection>();
-            mocks.ReplayAll();
-
-            var calculationGroup = new CalculationGroup();
-            var parent = new CalculationGroup();
-            var failureMechanism = new PipingFailureMechanism();
-            var context = new PipingCalculationGroupContext(calculationGroup,
-                                                            parent,
-                                                            new PipingSurfaceLine[0],
-                                                            new PipingStochasticSoilModel[0],
-                                                            failureMechanism,
-                                                            assessmentSection);
-
-            // Call
-            bool isEqual = context.Equals(null);
-
-            // Assert
-            Assert.IsFalse(isEqual);
-
-            mocks.VerifyAll();
-        }
-
-        [TestFixture]
+        [TestFixture(true)]
+        [TestFixture(false)]
         private class PipingCalculationGroupContextEqualsTest
             : EqualsTestFixture<PipingCalculationGroupContext, DerivedPipingCalculationGroupContext>
         {
@@ -113,9 +87,10 @@
             private static readonly IEnumerable<PipingSurfaceLine> surfaceLines = new PipingSurfaceLine[0];
             private static readonly IEnumerable<PipingStochasticSoilModel> stochasticSoilModels = new PipingStochasticSoilModel[0];
             private static readonly PipingFailureMechanism failureMechanism = new PipingFailureMechanism();
-            private static readonly CalculationGroup parent = new CalculationGroup();
             private static readonly CalculationGroup calculationGroup = new CalculationGroup();
 
+            private static CalculationGroup parent;
+
             [SetUp]
             public void SetUp()
             {
@@ -128,6 +103,11 @@
                 mocks.VerifyAll();
             }
 
+            public PipingCalculationGroupContextEqualsTest(bool hasParent)
+            {
+                parent = hasParent ? new CalculationGroup() : null;
+            }
+
             protected override PipingCalculationGroupContext CreateObject()
             {
                 return new PipingCalculationGroupContext(calculationGroup,