Index: Core/Gui/test/Core.Gui.TestUtil/Core.Gui.TestUtil.csproj
===================================================================
diff -u -r9d314bdfad94ff3fa9695732f06e4b541facb2a7 -r7d5b45bb235209809f53fabb6bd7b05cfff67765
--- Core/Gui/test/Core.Gui.TestUtil/Core.Gui.TestUtil.csproj	(.../Core.Gui.TestUtil.csproj)	(revision 9d314bdfad94ff3fa9695732f06e4b541facb2a7)
+++ Core/Gui/test/Core.Gui.TestUtil/Core.Gui.TestUtil.csproj	(.../Core.Gui.TestUtil.csproj)	(revision 7d5b45bb235209809f53fabb6bd7b05cfff67765)
@@ -24,6 +24,9 @@
     <PackageReference Include="AvalonDock">
       <Version>2.0.2000</Version>
     </PackageReference>
+    <PackageReference Include="NSubstitute">
+      <Version>4.4.0</Version>
+    </PackageReference>
     <PackageReference Include="NUnit">
       <Version>3.8.1</Version>
     </PackageReference>
Index: Core/Gui/test/Core.Gui.TestUtil/MainWindowTestHelper.cs
===================================================================
diff -u -r9339a780307cdb21ebe38cbd3aa8811e2c98d980 -r7d5b45bb235209809f53fabb6bd7b05cfff67765
--- Core/Gui/test/Core.Gui.TestUtil/MainWindowTestHelper.cs	(.../MainWindowTestHelper.cs)	(revision 9339a780307cdb21ebe38cbd3aa8811e2c98d980)
+++ Core/Gui/test/Core.Gui.TestUtil/MainWindowTestHelper.cs	(.../MainWindowTestHelper.cs)	(revision 7d5b45bb235209809f53fabb6bd7b05cfff67765)
@@ -23,6 +23,7 @@
 using System.Drawing;
 using Core.Gui.Forms.Main;
 using Rhino.Mocks;
+using NSubstitute;
 
 namespace Core.Gui.TestUtil
 {
@@ -45,5 +46,19 @@
 
             return mainWindow;
         }
+        
+        /// <summary>
+        /// Creates a new <see cref="IMainWindow"/> stub.
+        /// </summary>
+        /// <returns>The <see cref="IMainWindow"/> stub.</returns>
+        public static IMainWindow CreateMainWindowStub()
+        {
+            var mainWindow = Substitute.For<IMainWindow>();
+
+            mainWindow.ApplicationIcon.Returns(SystemIcons.Application);
+            mainWindow.Handle.Returns(IntPtr.Zero);
+
+            return mainWindow;
+        }
     }
 }
\ No newline at end of file
Index: Riskeer/WaveImpactAsphaltCover/test/Riskeer.WaveImpactAsphaltCover.Plugin.Test/TreeNodeInfos/WaveImpactAsphaltCoverWaveConditionsCalculationContextTreeNodeInfoTest.cs
===================================================================
diff -u -r9339a780307cdb21ebe38cbd3aa8811e2c98d980 -r7d5b45bb235209809f53fabb6bd7b05cfff67765
--- Riskeer/WaveImpactAsphaltCover/test/Riskeer.WaveImpactAsphaltCover.Plugin.Test/TreeNodeInfos/WaveImpactAsphaltCoverWaveConditionsCalculationContextTreeNodeInfoTest.cs	(.../WaveImpactAsphaltCoverWaveConditionsCalculationContextTreeNodeInfoTest.cs)	(revision 9339a780307cdb21ebe38cbd3aa8811e2c98d980)
+++ Riskeer/WaveImpactAsphaltCover/test/Riskeer.WaveImpactAsphaltCover.Plugin.Test/TreeNodeInfos/WaveImpactAsphaltCoverWaveConditionsCalculationContextTreeNodeInfoTest.cs	(.../WaveImpactAsphaltCoverWaveConditionsCalculationContextTreeNodeInfoTest.cs)	(revision 7d5b45bb235209809f53fabb6bd7b05cfff67765)
@@ -37,7 +37,7 @@
 using Core.Gui.TestUtil.ContextMenu;
 using NUnit.Extensions.Forms;
 using NUnit.Framework;
-using Rhino.Mocks;
+using NSubstitute;
 using Riskeer.Common.Data;
 using Riskeer.Common.Data.AssessmentSection;
 using Riskeer.Common.Data.Calculation;
@@ -69,16 +69,14 @@
         private static readonly string validHrdFilePath = Path.Combine(testDataPath, "HRD dutch coast south.sqlite");
         private static readonly string validHrdFileVersion = "Dutch coast South19-11-2015 12:0013";
 
-        private MockRepository mocks;
         private WaveImpactAsphaltCoverPlugin plugin;
         private TreeNodeInfo info;
 
         [Test]
         public void Initialized_Always_ExpectedPropertiesSet()
         {
             // Setup
-            mocks.ReplayAll();
-
+            
             // Assert
             Assert.IsNotNull(info.Text);
             Assert.IsNull(info.ForeColor);
@@ -104,9 +102,8 @@
         public void Text_Always_ReturnCalculationName()
         {
             // Setup
-            var assessmentSection = mocks.Stub<IAssessmentSection>();
-            mocks.ReplayAll();
-
+            var assessmentSection = Substitute.For<IAssessmentSection>();
+            
             const string name = "cool name";
             var parent = new CalculationGroup();
             var calculation = new WaveImpactAsphaltCoverWaveConditionsCalculation
@@ -130,8 +127,7 @@
         public void Image_Always_ReturnCalculationIcon()
         {
             // Setup
-            mocks.ReplayAll();
-
+            
             // Call
             Image icon = info.Image(null);
 
@@ -143,8 +139,7 @@
         public void EnsureVisibleOnCreate_Always_ReturnTrue()
         {
             // Setup
-            mocks.ReplayAll();
-
+            
             // Call
             bool shouldBeVisible = info.EnsureVisibleOnCreate(null, null);
 
@@ -156,8 +151,8 @@
         public void ChildNodeObjects_CalculationWithoutOutput_ReturnChildrenWithEmptyOutput()
         {
             // Setup
-            var assessmentSection = mocks.Stub<IAssessmentSection>();
-            assessmentSection.Stub(a => a.HydraulicBoundaryData).Return(new HydraulicBoundaryData
+            var assessmentSection = Substitute.For<IAssessmentSection>();
+            assessmentSection.HydraulicBoundaryData.Returns(new HydraulicBoundaryData
             {
                 HydraulicBoundaryDatabases =
                 {
@@ -170,8 +165,7 @@
                     }
                 }
             });
-            mocks.ReplayAll();
-
+            
             var parent = new CalculationGroup();
             var calculation = new WaveImpactAsphaltCoverWaveConditionsCalculation
             {
@@ -215,8 +209,8 @@
         public void ChildNodeObjects_CalculationWithOutput_ReturnChildrenWithOutput()
         {
             // Setup
-            var assessmentSection = mocks.Stub<IAssessmentSection>();
-            assessmentSection.Stub(a => a.HydraulicBoundaryData).Return(new HydraulicBoundaryData
+            var assessmentSection = Substitute.For<IAssessmentSection>();
+            assessmentSection.HydraulicBoundaryData.Returns(new HydraulicBoundaryData
             {
                 HydraulicBoundaryDatabases =
                 {
@@ -229,8 +223,7 @@
                     }
                 }
             });
-            mocks.ReplayAll();
-
+            
             var parent = new CalculationGroup();
             var calculation = new WaveImpactAsphaltCoverWaveConditionsCalculation
             {
@@ -274,8 +267,7 @@
         public void CanRename_Always_ReturnTrue()
         {
             // Setup
-            mocks.ReplayAll();
-
+            
             // Call
             bool canRename = info.CanRename(null, null);
 
@@ -287,10 +279,8 @@
         public void OnNodeRenamed_ChangeNameOfCalculationAndNotifyObservers()
         {
             // Setup
-            var assessmentSection = mocks.Stub<IAssessmentSection>();
-            var observer = mocks.StrictMock<IObserver>();
-            observer.Expect(o => o.UpdateObserver());
-            mocks.ReplayAll();
+            var assessmentSection = Substitute.For<IAssessmentSection>();
+            var observer = Substitute.For<IObserver>();
 
             var parent = new CalculationGroup();
             var calculation = new WaveImpactAsphaltCoverWaveConditionsCalculation
@@ -311,14 +301,14 @@
 
             // Assert
             Assert.AreEqual(name, calculation.Name);
+            observer.Received().UpdateObserver();
         }
 
         [Test]
         public void CanRemove_CalculationInParent_ReturnTrue()
         {
             // Setup
-            var assessmentSection = mocks.Stub<IAssessmentSection>();
-            mocks.ReplayAll();
+            var assessmentSection = Substitute.For<IAssessmentSection>();
 
             var parent = new CalculationGroup();
             var calculation = new WaveImpactAsphaltCoverWaveConditionsCalculation
@@ -348,8 +338,7 @@
         public void CanRemove_CalculationNotInParent_ReturnFalse()
         {
             // Setup
-            var assessmentSection = mocks.Stub<IAssessmentSection>();
-            mocks.ReplayAll();
+            var assessmentSection = Substitute.For<IAssessmentSection>();
 
             var parent = new CalculationGroup();
             var calculation = new WaveImpactAsphaltCoverWaveConditionsCalculation
@@ -378,10 +367,8 @@
         public void OnNodeRemoved_CalculationInParent_CalculationRemovedFromParent()
         {
             // Setup
-            var assessmentSection = mocks.Stub<IAssessmentSection>();
-            var observer = mocks.StrictMock<IObserver>();
-            observer.Expect(o => o.UpdateObserver());
-            mocks.ReplayAll();
+            var assessmentSection = Substitute.For<IAssessmentSection>();
+            var observer = Substitute.For<IObserver>();
 
             var parent = new CalculationGroup();
             var calculation = new WaveImpactAsphaltCoverWaveConditionsCalculation
@@ -411,9 +398,6 @@
         [Test]
         public void CanDrag_Always_ReturnTrue()
         {
-            // Setup
-            mocks.ReplayAll();
-
             // Call
             bool canDrag = info.CanDrag(null, null);
 
@@ -426,7 +410,7 @@
         {
             // Setup
             var failureMechanism = new WaveImpactAsphaltCoverFailureMechanism();
-            IAssessmentSection assessmentSection = AssessmentSectionTestHelper.CreateAssessmentSectionStub(mocks);
+            IAssessmentSection assessmentSection = new AssessmentSectionStub();
 
             var parent = new CalculationGroup();
             var calculation = new WaveImpactAsphaltCoverWaveConditionsCalculation();
@@ -435,53 +419,57 @@
                                                                                      failureMechanism,
                                                                                      assessmentSection);
 
-            var orderedMocks = new MockRepository();
-            var menuBuilder = orderedMocks.StrictMock<IContextMenuBuilder>();
-            using (orderedMocks.Ordered())
-            {
-                menuBuilder.Expect(mb => mb.AddExportItem()).Return(menuBuilder);
-                menuBuilder.Expect(mb => mb.AddSeparator()).Return(menuBuilder);
-                menuBuilder.Expect(mb => mb.AddCustomItem(null)).IgnoreArguments().Return(menuBuilder);
-                menuBuilder.Expect(mb => mb.AddSeparator()).Return(menuBuilder);
-                menuBuilder.Expect(mb => mb.AddRenameItem()).Return(menuBuilder);
-                menuBuilder.Expect(mb => mb.AddCustomItem(null)).IgnoreArguments().Return(menuBuilder);
-                menuBuilder.Expect(mb => mb.AddSeparator()).Return(menuBuilder);
-                menuBuilder.Expect(mb => mb.AddCustomItem(null)).IgnoreArguments().Return(menuBuilder);
-                menuBuilder.Expect(mb => mb.AddCustomItem(null)).IgnoreArguments().Return(menuBuilder);
-                menuBuilder.Expect(mb => mb.AddSeparator()).Return(menuBuilder);
-                menuBuilder.Expect(mb => mb.AddCustomItem(null)).IgnoreArguments().Return(menuBuilder);
-                menuBuilder.Expect(mb => mb.AddDeleteItem()).Return(menuBuilder);
-                menuBuilder.Expect(mb => mb.AddSeparator()).Return(menuBuilder);
-                menuBuilder.Expect(mb => mb.AddCollapseAllItem()).Return(menuBuilder);
-                menuBuilder.Expect(mb => mb.AddExpandAllItem()).Return(menuBuilder);
-                menuBuilder.Expect(mb => mb.AddSeparator()).Return(menuBuilder);
-                menuBuilder.Expect(mb => mb.AddPropertiesItem()).Return(menuBuilder);
-                menuBuilder.Expect(mb => mb.Build()).Return(null);
-            }
+            var menuBuilder = Substitute.For<IContextMenuBuilder>();
+            menuBuilder.AddExportItem().Returns(menuBuilder);
+            menuBuilder.AddSeparator().Returns(menuBuilder);
+            menuBuilder.AddCustomItem(Arg.Any<StrictContextMenuItem>()).Returns(menuBuilder);
+            menuBuilder.AddRenameItem().Returns(menuBuilder);
+            menuBuilder.AddDeleteItem().Returns(menuBuilder);
+            menuBuilder.AddCollapseAllItem().Returns(menuBuilder);
+            menuBuilder.AddExpandAllItem().Returns(menuBuilder);
+            menuBuilder.AddPropertiesItem().Returns(menuBuilder);
+            menuBuilder.Build().Returns((ContextMenuStrip) null);
 
             using (var treeViewControl = new TreeViewControl())
             {
-                var gui = mocks.Stub<IGui>();
-                gui.Stub(g => g.Get(context, treeViewControl)).Return(menuBuilder);
-                gui.Stub(cmp => cmp.MainWindow).Return(mocks.Stub<IMainWindow>());
-                mocks.ReplayAll();
-                orderedMocks.ReplayAll();
+                var gui = Substitute.For<IGui>();
+                gui.Get(context, treeViewControl).Returns(menuBuilder);
+                gui.MainWindow.Returns(Substitute.For<IMainWindow>());
 
                 plugin.Gui = gui;
 
                 // Call
                 info.ContextMenuStrip(context, null, treeViewControl);
             }
 
-            // Assert
-            orderedMocks.VerifyAll();
+            Received.InOrder(() =>
+            {
+                menuBuilder.AddExportItem();
+                menuBuilder.AddSeparator();
+                menuBuilder.AddCustomItem(Arg.Any<StrictContextMenuItem>());
+                menuBuilder.AddSeparator();
+                menuBuilder.AddRenameItem();
+                menuBuilder.AddCustomItem(Arg.Any<StrictContextMenuItem>());
+                menuBuilder.AddSeparator();
+                menuBuilder.AddCustomItem(Arg.Any<StrictContextMenuItem>());
+                menuBuilder.AddCustomItem(Arg.Any<StrictContextMenuItem>());
+                menuBuilder.AddSeparator();
+                menuBuilder.AddCustomItem(Arg.Any<StrictContextMenuItem>());
+                menuBuilder.AddDeleteItem();
+                menuBuilder.AddSeparator();
+                menuBuilder.AddCollapseAllItem();
+                menuBuilder.AddExpandAllItem();
+                menuBuilder.AddSeparator();
+                menuBuilder.AddPropertiesItem();
+                menuBuilder.Build();
+            });
         }
 
         [Test]
         public void ContextMenuStrip_Always_AddCustomItems()
         {
             // Setup
-            var assessmentSection = mocks.Stub<IAssessmentSection>();
+            var assessmentSection = Substitute.For<IAssessmentSection>();
             var failureMechanism = new WaveImpactAsphaltCoverFailureMechanism();
             var parent = new CalculationGroup();
             var calculation = new WaveImpactAsphaltCoverWaveConditionsCalculation();
@@ -493,11 +481,10 @@
 
             using (var treeViewControl = new TreeViewControl())
             {
-                var gui = mocks.Stub<IGui>();
-                gui.Stub(cmp => cmp.Get(context, treeViewControl)).Return(menuBuilder);
-                gui.Stub(cmp => cmp.MainWindow).Return(mocks.Stub<IMainWindow>());
-                mocks.ReplayAll();
-
+                var gui = Substitute.For<IGui>();
+                gui.Get(context, treeViewControl).Returns(menuBuilder);
+                gui.MainWindow.Returns(Substitute.For<IMainWindow>());
+                
                 plugin.Gui = gui;
 
                 // Call
@@ -542,7 +529,7 @@
             // Given
             var failureMechanism = new WaveImpactAsphaltCoverFailureMechanism();
 
-            var assessmentSection = mocks.Stub<IAssessmentSection>();
+            var assessmentSection = Substitute.For<IAssessmentSection>();
 
             var parent = new CalculationGroup();
             var calculation = new WaveImpactAsphaltCoverWaveConditionsCalculation
@@ -556,11 +543,11 @@
 
             using (var treeViewControl = new TreeViewControl())
             {
-                var appFeatureCommandHandler = mocks.Stub<IApplicationFeatureCommands>();
-                var importHandler = mocks.Stub<IImportCommandHandler>();
-                var exportHandler = mocks.Stub<IExportCommandHandler>();
-                var updateHandler = mocks.Stub<IUpdateCommandHandler>();
-                var viewCommands = mocks.Stub<IViewCommands>();
+                var appFeatureCommandHandler = Substitute.For<IApplicationFeatureCommands>();
+                var importHandler = Substitute.For<IImportCommandHandler>();
+                var exportHandler = Substitute.For<IExportCommandHandler>();
+                var updateHandler = Substitute.For<IUpdateCommandHandler>();
+                var viewCommands = Substitute.For<IViewCommands>();
                 var menuBuilder = new ContextMenuBuilder(appFeatureCommandHandler,
                                                          importHandler,
                                                          exportHandler,
@@ -569,11 +556,10 @@
                                                          context,
                                                          treeViewControl);
 
-                var gui = mocks.Stub<IGui>();
-                gui.Stub(g => g.Get(context, treeViewControl)).Return(menuBuilder);
-                gui.Stub(cmp => cmp.MainWindow).Return(mocks.Stub<IMainWindow>());
-                mocks.ReplayAll();
-
+                var gui = Substitute.For<IGui>();
+                gui.Get(context, treeViewControl).Returns(menuBuilder);
+                gui.MainWindow.Returns(Substitute.For<IMainWindow>());
+                
                 plugin.Gui = gui;
 
                 using (ContextMenuStrip contextMenu = info.ContextMenuStrip(context, null, treeViewControl))
@@ -592,7 +578,7 @@
         public void ContextMenuStrip_CalculationWithoutForeshoreProfile_ContextMenuItemUpdateForeshoreProfileDisabledAndToolTipSet()
         {
             // Setup
-            IAssessmentSection assessmentSection = AssessmentSectionTestHelper.CreateAssessmentSectionStub(mocks);
+            IAssessmentSection assessmentSection = new AssessmentSectionStub();
             var failureMechanism = new WaveImpactAsphaltCoverFailureMechanism();
             var parent = new CalculationGroup();
             var calculation = new WaveImpactAsphaltCoverWaveConditionsCalculation();
@@ -604,10 +590,9 @@
 
             using (var treeViewControl = new TreeViewControl())
             {
-                var gui = mocks.Stub<IGui>();
-                gui.Stub(cmp => cmp.Get(nodeData, treeViewControl)).Return(new CustomItemsOnlyContextMenuBuilder());
-                gui.Stub(cmp => cmp.MainWindow).Return(mocks.Stub<IMainWindow>());
-                mocks.ReplayAll();
+                var gui = Substitute.For<IGui>();
+                gui.Get(nodeData, treeViewControl).Returns(new CustomItemsOnlyContextMenuBuilder());
+                gui.MainWindow.Returns(Substitute.For<IMainWindow>());
 
                 plugin.Gui = gui;
 
@@ -630,7 +615,7 @@
         public void ContextMenuStrip_CalculationWithForeshoreProfileAndInputInSync_ContextMenuItemUpdateForeshoreProfileDisabledAndToolTipSet()
         {
             // Setup
-            IAssessmentSection assessmentSection = AssessmentSectionTestHelper.CreateAssessmentSectionStub(mocks);
+            IAssessmentSection assessmentSection = new AssessmentSectionStub();
             var failureMechanism = new WaveImpactAsphaltCoverFailureMechanism();
             var parent = new CalculationGroup();
             var calculation = new WaveImpactAsphaltCoverWaveConditionsCalculation
@@ -648,10 +633,9 @@
 
             using (var treeViewControl = new TreeViewControl())
             {
-                var gui = mocks.Stub<IGui>();
-                gui.Stub(cmp => cmp.Get(nodeData, treeViewControl)).Return(new CustomItemsOnlyContextMenuBuilder());
-                gui.Stub(cmp => cmp.MainWindow).Return(mocks.Stub<IMainWindow>());
-                mocks.ReplayAll();
+                var gui = Substitute.For<IGui>();
+                gui.Get(nodeData, treeViewControl).Returns(new CustomItemsOnlyContextMenuBuilder());
+                gui.MainWindow.Returns(Substitute.For<IMainWindow>());
 
                 plugin.Gui = gui;
 
@@ -674,7 +658,7 @@
         public void ContextMenuStrip_CalculationWithForeshoreProfileAndInputOutSync_ContextMenuItemUpdateForeshoreProfileEnabledAndToolTipSet()
         {
             // Setup
-            IAssessmentSection assessmentSection = AssessmentSectionTestHelper.CreateAssessmentSectionStub(mocks);
+            IAssessmentSection assessmentSection = new AssessmentSectionStub();
             var failureMechanism = new WaveImpactAsphaltCoverFailureMechanism();
 
             var foreshoreProfileInput = new TestForeshoreProfile();
@@ -695,10 +679,9 @@
 
             using (var treeViewControl = new TreeViewControl())
             {
-                var gui = mocks.Stub<IGui>();
-                gui.Stub(cmp => cmp.Get(nodeData, treeViewControl)).Return(new CustomItemsOnlyContextMenuBuilder());
-                gui.Stub(cmp => cmp.MainWindow).Return(mocks.Stub<IMainWindow>());
-                mocks.ReplayAll();
+                var gui = Substitute.For<IGui>();
+                gui.Get(nodeData, treeViewControl).Returns(new CustomItemsOnlyContextMenuBuilder());
+                gui.MainWindow.Returns(Substitute.For<IMainWindow>());
 
                 plugin.Gui = gui;
 
@@ -720,11 +703,10 @@
         public void GivenCalculationWithoutOutputAndWithInputOutOfSync_WhenUpdateForeshoreProfileClicked_ThenNoInquiryAndCalculationUpdatedAndInputObserverNotified()
         {
             // Given
-            var calculationObserver = mocks.StrictMock<IObserver>();
-            var calculationInputObserver = mocks.StrictMock<IObserver>();
-            calculationInputObserver.Expect(o => o.UpdateObserver());
+            var calculationObserver = Substitute.For<IObserver>();
+            var calculationInputObserver = Substitute.For<IObserver>();
 
-            IAssessmentSection assessmentSection = AssessmentSectionTestHelper.CreateAssessmentSectionStub(mocks);
+            IAssessmentSection assessmentSection = new AssessmentSectionStub();
             var failureMechanism = new WaveImpactAsphaltCoverFailureMechanism();
 
             var foreshoreProfileInput = new TestForeshoreProfile(true);
@@ -746,11 +728,10 @@
 
             using (var treeViewControl = new TreeViewControl())
             {
-                var gui = mocks.Stub<IGui>();
-                gui.Stub(g => g.Get(nodeData, treeViewControl)).Return(new CustomItemsOnlyContextMenuBuilder());
-                gui.Stub(cmp => cmp.MainWindow).Return(mocks.Stub<IMainWindow>());
-                mocks.ReplayAll();
-
+                var gui = Substitute.For<IGui>();
+                gui.Get(nodeData, treeViewControl).Returns(new CustomItemsOnlyContextMenuBuilder());
+                gui.MainWindow.Returns(Substitute.For<IMainWindow>());
+                
                 plugin.Gui = gui;
 
                 TestForeshoreProfile.ChangeBreakWaterProperties(foreshoreProfileInput);
@@ -767,6 +748,7 @@
                     Assert.IsTrue(calculation.InputParameters.IsForeshoreProfileInputSynchronized);
                 }
             }
+            calculationInputObserver.Received().UpdateObserver();
         }
 
         [Test]
@@ -775,9 +757,9 @@
         public void GivenCalculationWithOutputAndWithInputOutOfSync_WhenPerformClick_ThenInquiryAndExpectedOutputAndNotifications(bool continuation)
         {
             // Given
-            var calculationObserver = mocks.StrictMock<IObserver>();
-            var calculationInputObserver = mocks.StrictMock<IObserver>();
-            IAssessmentSection assessmentSection = AssessmentSectionTestHelper.CreateAssessmentSectionStub(mocks);
+            var calculationObserver = Substitute.For<IObserver>();
+            var calculationInputObserver = Substitute.For<IObserver>();
+            IAssessmentSection assessmentSection = new AssessmentSectionStub();
             var failureMechanism = new WaveImpactAsphaltCoverFailureMechanism();
 
             var foreshoreProfileInput = new TestForeshoreProfile(true);
@@ -799,12 +781,6 @@
             calculation.Attach(calculationObserver);
             calculation.InputParameters.Attach(calculationInputObserver);
 
-            if (continuation)
-            {
-                calculationObserver.Expect(o => o.UpdateObserver());
-                calculationInputObserver.Expect(o => o.UpdateObserver());
-            }
-
             var messageBoxText = "";
             DialogBoxHandler = (name, wnd) =>
             {
@@ -823,11 +799,10 @@
 
             using (var treeViewControl = new TreeViewControl())
             {
-                var gui = mocks.Stub<IGui>();
-                gui.Stub(g => g.Get(nodeData, treeViewControl)).Return(new CustomItemsOnlyContextMenuBuilder());
-                gui.Stub(cmp => cmp.MainWindow).Return(mocks.Stub<IMainWindow>());
-                mocks.ReplayAll();
-
+                var gui = Substitute.For<IGui>();
+                gui.Get(nodeData, treeViewControl).Returns(new CustomItemsOnlyContextMenuBuilder());
+                gui.MainWindow.Returns(Substitute.For<IMainWindow>());
+                
                 plugin.Gui = gui;
 
                 TestForeshoreProfile.ChangeBreakWaterProperties(foreshoreProfileInput);
@@ -850,6 +825,12 @@
                                             $"verwijderd.{Environment.NewLine}{Environment.NewLine}Weet u zeker dat u wilt doorgaan?";
 
             Assert.AreEqual(expectedMessageBoxText, messageBoxText);
+            
+            if (continuation)
+            {
+                calculationObserver.Received().UpdateObserver();
+                calculationInputObserver.Received().UpdateObserver();
+            }
         }
 
         [Test]
@@ -876,11 +857,11 @@
 
             using (var treeViewControl = new TreeViewControl())
             {
-                var appFeatureCommandHandler = mocks.Stub<IApplicationFeatureCommands>();
-                var importHandler = mocks.Stub<IImportCommandHandler>();
-                var exportHandler = mocks.Stub<IExportCommandHandler>();
-                var updateHandler = mocks.Stub<IUpdateCommandHandler>();
-                var viewCommands = mocks.Stub<IViewCommands>();
+                var appFeatureCommandHandler = Substitute.For<IApplicationFeatureCommands>();
+                var importHandler = Substitute.For<IImportCommandHandler>();
+                var exportHandler = Substitute.For<IExportCommandHandler>();
+                var updateHandler = Substitute.For<IUpdateCommandHandler>();
+                var viewCommands = Substitute.For<IViewCommands>();
                 var menuBuilder = new ContextMenuBuilder(appFeatureCommandHandler,
                                                          importHandler,
                                                          exportHandler,
@@ -889,10 +870,9 @@
                                                          context,
                                                          treeViewControl);
 
-                var gui = mocks.Stub<IGui>();
-                gui.Stub(g => g.Get(context, treeViewControl)).Return(menuBuilder);
-                gui.Stub(cmp => cmp.MainWindow).Return(mocks.Stub<IMainWindow>());
-                mocks.ReplayAll();
+                var gui = Substitute.For<IGui>();
+                gui.Get(context, treeViewControl).Returns(menuBuilder);
+                gui.MainWindow.Returns(Substitute.For<IMainWindow>());
 
                 plugin.Gui = gui;
 
@@ -929,7 +909,7 @@
             // Given
             var failureMechanism = new WaveImpactAsphaltCoverFailureMechanism();
 
-            var assessmentSection = mocks.Stub<IAssessmentSection>();
+            var assessmentSection = Substitute.For<IAssessmentSection>();
 
             var parent = new CalculationGroup();
             var calculation = new WaveImpactAsphaltCoverWaveConditionsCalculation
@@ -943,11 +923,11 @@
 
             using (var treeViewControl = new TreeViewControl())
             {
-                var appFeatureCommandHandler = mocks.Stub<IApplicationFeatureCommands>();
-                var importHandler = mocks.Stub<IImportCommandHandler>();
-                var exportHandler = mocks.Stub<IExportCommandHandler>();
-                var updateHandler = mocks.Stub<IUpdateCommandHandler>();
-                var viewCommands = mocks.Stub<IViewCommands>();
+                var appFeatureCommandHandler = Substitute.For<IApplicationFeatureCommands>();
+                var importHandler = Substitute.For<IImportCommandHandler>();
+                var exportHandler = Substitute.For<IExportCommandHandler>();
+                var updateHandler = Substitute.For<IUpdateCommandHandler>();
+                var viewCommands = Substitute.For<IViewCommands>();
                 var menuBuilder = new ContextMenuBuilder(appFeatureCommandHandler,
                                                          importHandler,
                                                          exportHandler,
@@ -956,10 +936,9 @@
                                                          context,
                                                          treeViewControl);
 
-                var gui = mocks.Stub<IGui>();
-                gui.Stub(g => g.Get(context, treeViewControl)).Return(menuBuilder);
-                gui.Stub(cmp => cmp.MainWindow).Return(mocks.Stub<IMainWindow>());
-                mocks.ReplayAll();
+                var gui = Substitute.For<IGui>();
+                gui.Get(context, treeViewControl).Returns(menuBuilder);
+                gui.MainWindow.Returns(Substitute.For<IMainWindow>());
 
                 plugin.Gui = gui;
 
@@ -999,45 +978,41 @@
 
             using (var treeViewControl = new TreeViewControl())
             {
-                var appFeatureCommandHandler = mocks.Stub<IApplicationFeatureCommands>();
-                var importHandler = mocks.Stub<IImportCommandHandler>();
-                var exportHandler = mocks.Stub<IExportCommandHandler>();
-                var updateHandler = mocks.Stub<IUpdateCommandHandler>();
-                var viewCommands = mocks.Stub<IViewCommands>();
+                var appFeatureCommandHandler = Substitute.For<IApplicationFeatureCommands>();
+                var importHandler = Substitute.For<IImportCommandHandler>();
+                var exportHandler = Substitute.For<IExportCommandHandler>();
+                var updateHandler = Substitute.For<IUpdateCommandHandler>();
+                var viewCommands = Substitute.For<IViewCommands>();
                 var menuBuilder = new ContextMenuBuilder(appFeatureCommandHandler,
                                                          importHandler,
                                                          exportHandler,
                                                          updateHandler,
                                                          viewCommands,
                                                          context,
                                                          treeViewControl);
-                var observer = mocks.StrictMock<IObserver>();
-                observer.Expect(o => o.UpdateObserver());
+                var observer = Substitute.For<IObserver>();
                 calculation.Attach(observer);
 
-                IMainWindow mainWindow = MainWindowTestHelper.CreateMainWindowStub(mocks);
+                IMainWindow mainWindow = MainWindowTestHelper.CreateMainWindowStub();
 
-                var gui = mocks.Stub<IGui>();
-                gui.Stub(g => g.Get(context, treeViewControl)).Return(menuBuilder);
-                gui.Stub(g => g.MainWindow).Return(mainWindow);
+                var gui = Substitute.For<IGui>();
+                gui.Get(context, treeViewControl).Returns(menuBuilder);
+                gui.MainWindow.Returns(mainWindow);
 
                 RoundedDouble assessmentLevel = WaveConditionsInputHelper.GetAssessmentLevel(calculation.InputParameters, assessmentSection);
                 IEnumerable<RoundedDouble> waterLevels = calculation.InputParameters.GetWaterLevels(assessmentLevel);
                 int nrOfCalculators = waterLevels.Count();
-                var calculatorFactory = mocks.Stub<IHydraRingCalculatorFactory>();
-                calculatorFactory.Expect(cf => cf.CreateWaveConditionsCosineCalculator(Arg<HydraRingCalculationSettings>.Is.NotNull))
-                                 .WhenCalled(invocation =>
+                var calculatorFactory = Substitute.For<IHydraRingCalculatorFactory>();
+                calculatorFactory.CreateWaveConditionsCosineCalculator(Arg.Any<HydraRingCalculationSettings>())
+                                 .Returns(callInfo =>
                                  {
                                      HydraRingCalculationSettingsTestHelper.AssertHydraRingCalculationSettings(
                                          HydraulicBoundaryCalculationSettingsFactory.CreateSettings(
                                              assessmentSection.HydraulicBoundaryData,
                                              hydraulicBoundaryLocation),
-                                         (HydraRingCalculationSettings) invocation.Arguments[0]);
-                                 })
-                                 .Return(new TestWaveConditionsCosineCalculator())
-                                 .Repeat
-                                 .Times(nrOfCalculators);
-                mocks.ReplayAll();
+                                         (HydraRingCalculationSettings) callInfo[0]);
+                                     return new TestWaveConditionsCosineCalculator();
+                                 });
 
                 plugin.Gui = gui;
 
@@ -1058,7 +1033,10 @@
                         CalculationServiceTestHelper.AssertCalculationEndMessage(messages[13]);
                         Assert.AreEqual("Golfcondities berekenen voor 'A' is gelukt.", messages[14]);
                     });
+                    calculatorFactory.Received(nrOfCalculators)
+                                     .CreateWaveConditionsCosineCalculator(Arg.Any<HydraRingCalculationSettings>());
                     Assert.AreEqual(3, calculation.Output.Items.Count());
+                    observer.Received().UpdateObserver();
                 }
             }
         }
@@ -1068,7 +1046,7 @@
         {
             // Given
             var failureMechanism = new WaveImpactAsphaltCoverFailureMechanism();
-            IAssessmentSection assessmentSection = AssessmentSectionTestHelper.CreateAssessmentSectionStub(mocks);
+            IAssessmentSection assessmentSection = new AssessmentSectionStub();
 
             var parent = new CalculationGroup();
             var calculation = new WaveImpactAsphaltCoverWaveConditionsCalculation
@@ -1083,11 +1061,11 @@
 
             using (var treeViewControl = new TreeViewControl())
             {
-                var appFeatureCommandHandler = mocks.Stub<IApplicationFeatureCommands>();
-                var importHandler = mocks.Stub<IImportCommandHandler>();
-                var exportHandler = mocks.Stub<IExportCommandHandler>();
-                var updateHandler = mocks.Stub<IUpdateCommandHandler>();
-                var viewCommands = mocks.Stub<IViewCommands>();
+                var appFeatureCommandHandler = Substitute.For<IApplicationFeatureCommands>();
+                var importHandler = Substitute.For<IImportCommandHandler>();
+                var exportHandler = Substitute.For<IExportCommandHandler>();
+                var updateHandler = Substitute.For<IUpdateCommandHandler>();
+                var viewCommands = Substitute.For<IViewCommands>();
                 var menuBuilder = new ContextMenuBuilder(appFeatureCommandHandler,
                                                          importHandler,
                                                          exportHandler,
@@ -1096,11 +1074,10 @@
                                                          context,
                                                          treeViewControl);
 
-                var gui = mocks.Stub<IGui>();
-                gui.Stub(g => g.Get(context, treeViewControl)).Return(menuBuilder);
-                gui.Stub(cmp => cmp.MainWindow).Return(mocks.Stub<IMainWindow>());
-                mocks.ReplayAll();
-
+                var gui = Substitute.For<IGui>();
+                gui.Get(context, treeViewControl).Returns(menuBuilder);
+                gui.MainWindow.Returns(Substitute.For<IMainWindow>());
+                
                 plugin.Gui = gui;
 
                 using (ContextMenuStrip contextMenu = info.ContextMenuStrip(context, null, treeViewControl))
@@ -1121,7 +1098,7 @@
         {
             // Given
             var failureMechanism = new WaveImpactAsphaltCoverFailureMechanism();
-            IAssessmentSection assessmentSection = AssessmentSectionTestHelper.CreateAssessmentSectionStub(mocks);
+            IAssessmentSection assessmentSection = new AssessmentSectionStub();
 
             var parent = new CalculationGroup();
             var calculation = new WaveImpactAsphaltCoverWaveConditionsCalculation
@@ -1136,11 +1113,11 @@
 
             using (var treeViewControl = new TreeViewControl())
             {
-                var appFeatureCommandHandler = mocks.Stub<IApplicationFeatureCommands>();
-                var importHandler = mocks.Stub<IImportCommandHandler>();
-                var exportHandler = mocks.Stub<IExportCommandHandler>();
-                var updateHandler = mocks.Stub<IUpdateCommandHandler>();
-                var viewCommands = mocks.Stub<IViewCommands>();
+                var appFeatureCommandHandler = Substitute.For<IApplicationFeatureCommands>();
+                var importHandler = Substitute.For<IImportCommandHandler>();
+                var exportHandler = Substitute.For<IExportCommandHandler>();
+                var updateHandler = Substitute.For<IUpdateCommandHandler>();
+                var viewCommands = Substitute.For<IViewCommands>();
                 var menuBuilder = new ContextMenuBuilder(appFeatureCommandHandler,
                                                          importHandler,
                                                          exportHandler,
@@ -1149,11 +1126,10 @@
                                                          context,
                                                          treeViewControl);
 
-                var gui = mocks.Stub<IGui>();
-                gui.Stub(g => g.Get(context, treeViewControl)).Return(menuBuilder);
-                gui.Stub(cmp => cmp.MainWindow).Return(mocks.Stub<IMainWindow>());
-                mocks.ReplayAll();
-
+                var gui = Substitute.For<IGui>();
+                gui.Get(context, treeViewControl).Returns(menuBuilder);
+                gui.MainWindow.Returns(Substitute.For<IMainWindow>());
+                
                 plugin.Gui = gui;
 
                 using (ContextMenuStrip contextMenu = info.ContextMenuStrip(context, null, treeViewControl))
@@ -1173,10 +1149,9 @@
         {
             // Given
             var failureMechanism = new WaveImpactAsphaltCoverFailureMechanism();
-            IAssessmentSection assessmentSection = AssessmentSectionTestHelper.CreateAssessmentSectionStub(mocks);
+            IAssessmentSection assessmentSection = new AssessmentSectionStub();
 
-            var observer = mocks.Stub<IObserver>();
-            observer.Expect(o => o.UpdateObserver());
+            var observer = Substitute.For<IObserver>();
 
             var parent = new CalculationGroup();
             var calculation = new WaveImpactAsphaltCoverWaveConditionsCalculation
@@ -1192,11 +1167,11 @@
 
             using (var treeViewControl = new TreeViewControl())
             {
-                var appFeatureCommandHandler = mocks.Stub<IApplicationFeatureCommands>();
-                var importHandler = mocks.Stub<IImportCommandHandler>();
-                var exportHandler = mocks.Stub<IExportCommandHandler>();
-                var updateHandler = mocks.Stub<IUpdateCommandHandler>();
-                var viewCommands = mocks.Stub<IViewCommands>();
+                var appFeatureCommandHandler = Substitute.For<IApplicationFeatureCommands>();
+                var importHandler = Substitute.For<IImportCommandHandler>();
+                var exportHandler = Substitute.For<IExportCommandHandler>();
+                var updateHandler = Substitute.For<IUpdateCommandHandler>();
+                var viewCommands = Substitute.For<IViewCommands>();
                 var menuBuilder = new ContextMenuBuilder(appFeatureCommandHandler,
                                                          importHandler,
                                                          exportHandler,
@@ -1205,11 +1180,10 @@
                                                          context,
                                                          treeViewControl);
 
-                var gui = mocks.Stub<IGui>();
-                gui.Stub(g => g.Get(context, treeViewControl)).Return(menuBuilder);
-                gui.Stub(cmp => cmp.MainWindow).Return(mocks.Stub<IMainWindow>());
-                mocks.ReplayAll();
-
+                var gui = Substitute.For<IGui>();
+                gui.Get(context, treeViewControl).Returns(menuBuilder);
+                gui.MainWindow.Returns(Substitute.For<IMainWindow>());
+                
                 plugin.Gui = gui;
 
                 DialogBoxHandler = (name, wnd) =>
@@ -1226,22 +1200,20 @@
 
                     // Then
                     Assert.IsNull(calculation.Output);
-                    // Check expectancies in TearDown()
+                    observer.Received().UpdateObserver();
                 }
             }
         }
 
         public override void Setup()
         {
-            mocks = new MockRepository();
             plugin = new WaveImpactAsphaltCoverPlugin();
             info = plugin.GetTreeNodeInfos().First(tni => tni.TagType == typeof(WaveImpactAsphaltCoverWaveConditionsCalculationContext));
         }
 
         public override void TearDown()
         {
             plugin.Dispose();
-            mocks.VerifyAll();
             base.TearDown();
         }