Index: Ringtoets/Integration/src/Ringtoets.Integration.Plugin/RingtoetsPlugin.cs
===================================================================
diff -u -r1eed3e3f652618c52a462edc502cfd4250772314 -r1e2b39b01c3c7e64af8c8c2ab1b54b522c9fdd4b
--- Ringtoets/Integration/src/Ringtoets.Integration.Plugin/RingtoetsPlugin.cs	(.../RingtoetsPlugin.cs)	(revision 1eed3e3f652618c52a462edc502cfd4250772314)
+++ Ringtoets/Integration/src/Ringtoets.Integration.Plugin/RingtoetsPlugin.cs	(.../RingtoetsPlugin.cs)	(revision 1e2b39b01c3c7e64af8c8c2ab1b54b522c9fdd4b)
@@ -253,18 +253,23 @@
 
         public void SetAssessmentSectionToProject(RingtoetsProject ringtoetsProject, AssessmentSection assessmentSection)
         {
+            if (ringtoetsProject == null)
+            {
+                throw new ArgumentNullException("ringtoetsProject");
+            }
             if (assessmentSection == null)
             {
-                return;
+                throw new ArgumentNullException("assessmentSection");
             }
+
             assessmentSection.Name = GetUniqueForAssessmentSectionName(ringtoetsProject.Items, assessmentSection.Name);
             ringtoetsProject.Items.Add(assessmentSection);
             ringtoetsProject.NotifyObservers();
 
-            if (Gui != null && (Gui.Selection == null || Gui.Selection.Equals(assessmentSection)))
+            if (Gui != null && (Gui.Selection == null || !Gui.Selection.Equals(assessmentSection)))
             {
                 Gui.Selection = assessmentSection;
-                Gui.DocumentViewController.OpenViewForData(Gui.Selection);
+                Gui.DocumentViewController.OpenViewForData(assessmentSection);
             }
         }
 
@@ -372,6 +377,7 @@
 
             if (assessmentSection == null)
             {
+                return Enumerable.Empty<DataItemInfo>();
             }
 
             return new DataItemInfo[]
@@ -556,6 +562,10 @@
         private void SetAssessmentSectionFromFileToProject(RingtoetsProject ringtoetsProject)
         {
             var assessmentSection = GetAssessmentSectionFromFile();
+            if (!(assessmentSection is AssessmentSection))
+            {
+                return;
+            }
             SetAssessmentSectionToProject(ringtoetsProject, (AssessmentSection) assessmentSection);
         }
 
Index: Ringtoets/Integration/test/Ringtoets.Integration.Plugin.Test/RingtoetsPluginTest.cs
===================================================================
diff -u -r1eed3e3f652618c52a462edc502cfd4250772314 -r1e2b39b01c3c7e64af8c8c2ab1b54b522c9fdd4b
--- Ringtoets/Integration/test/Ringtoets.Integration.Plugin.Test/RingtoetsPluginTest.cs	(.../RingtoetsPluginTest.cs)	(revision 1eed3e3f652618c52a462edc502cfd4250772314)
+++ Ringtoets/Integration/test/Ringtoets.Integration.Plugin.Test/RingtoetsPluginTest.cs	(.../RingtoetsPluginTest.cs)	(revision 1e2b39b01c3c7e64af8c8c2ab1b54b522c9fdd4b)
@@ -24,13 +24,14 @@
 using System.IO;
 using System.Linq;
 using System.Windows.Threading;
-using Core.Common.Base.Data;
+using Core.Common.Base;
 using Core.Common.Base.IO;
 using Core.Common.Base.Storage;
 using Core.Common.Controls.TreeView;
 using Core.Common.Gui;
 using Core.Common.Gui.ContextMenu;
 using Core.Common.Gui.Forms.MainWindow;
+using Core.Common.Gui.Forms.ViewHost;
 using Core.Common.Gui.Plugin;
 using Core.Common.Gui.Settings;
 using Core.Common.TestUtil;
@@ -427,43 +428,213 @@
         public void GetChildDataWithViewDefinitions_UnsupportedData_ReturnEmpty()
         {
             // Setup
-            var plugin = new RingtoetsPlugin();
+            using (var plugin = new RingtoetsPlugin())
+            {
+                // Call
+                var childrenWithViewDefinitions = plugin.GetChildDataWithViewDefinitions(1);
 
-            // Call
-            var childrenWithViewDefinitions = plugin.GetChildDataWithViewDefinitions(1);
+                // Assert
+                CollectionAssert.IsEmpty(childrenWithViewDefinitions);
+            }
+        }
 
+        [Test]
+        public void GetFileImporters_ReturnsExpectedFileImporters()
+        {
+            // Setup
+            using (var plugin = new RingtoetsPlugin())
+            {
+                // Call
+                IFileImporter[] importers = plugin.GetFileImporters().ToArray();
+
+                // Assert
+                Assert.AreEqual(2, importers.Length);
+                Assert.AreEqual(1, importers.Count(i => i is ReferenceLineImporter));
+                Assert.AreEqual(1, importers.Count(i => i is FailureMechanismSectionsImporter));
+            }
+        }
+
+        [Test]
+        public void SetAssessmentSectionToProject_ProjectIsNull_ThrowsArgumentNullException()
+        {
+            // Setup
+            var assessmentSection = new AssessmentSection(AssessmentSectionComposition.Dike);
+            using (var plugin = new RingtoetsPlugin())
+            {
+                // Call
+                TestDelegate call = () => plugin.SetAssessmentSectionToProject(null, assessmentSection);
+
+                // Assert
+                var paramName = Assert.Throws<ArgumentNullException>(call).ParamName;
+                Assert.AreEqual("ringtoetsProject", paramName);
+            }
+        }
+
+        [Test]
+        public void SetAssessmentSectionToProject_AssessmentSectionIsNull_ThrowsArgumentNullException()
+        {
+            // Setup
+            var project = new RingtoetsProject();
+            using (var plugin = new RingtoetsPlugin())
+            {
+                // Call
+                TestDelegate call = () => plugin.SetAssessmentSectionToProject(project, null);
+
+                // Assert
+                var paramName = Assert.Throws<ArgumentNullException>(call).ParamName;
+                Assert.AreEqual("assessmentSection", paramName);
+            }
+        }
+
+        [Test]
+        public void SetAssessmentSectionToProject_WithData_UpdateDataAndNotifyObservers()
+        {
+            // Setup
+            var mockRepository = new MockRepository();
+            var projectObserver = mockRepository.StrictMock<IObserver>();
+            projectObserver.Expect(o => o.UpdateObserver());
+            mockRepository.ReplayAll();
+
+            var project = new RingtoetsProject();
+            var assessmentSection = new AssessmentSection(AssessmentSectionComposition.Dike);
+            using (var plugin = new RingtoetsPlugin())
+            {
+                project.Attach(projectObserver);
+
+                // Precondition
+                CollectionAssert.IsEmpty(project.Items);
+
+                // Call
+                plugin.SetAssessmentSectionToProject(project, assessmentSection);
+            }
             // Assert
-            CollectionAssert.IsEmpty(childrenWithViewDefinitions);
+            Assert.AreEqual(1, project.Items.Count);
+            CollectionAssert.Contains(project.Items, assessmentSection);
+            mockRepository.VerifyAll();
         }
 
         [Test]
-        public void GetFileImporters_ReturnsExpectedFileImporters()
+        public void SetAssessmentSectionToProject_NoSelectionSet_SelectionSetUpdated()
         {
             // Setup
-            var plugin = new RingtoetsPlugin();
+            var mockRepository = new MockRepository();
+            var assessmentSection = new AssessmentSection(AssessmentSectionComposition.Dike);
 
-            // Call
-            IFileImporter[] importers = plugin.GetFileImporters().ToArray();
+            var documentViewControllerMock = mockRepository.StrictMock<IDocumentViewController>();
+            documentViewControllerMock.Expect(d => d.OpenViewForData(assessmentSection)).Return(true);
 
+            var guiMock = mockRepository.StrictMock<IGui>();
+            guiMock.Stub(g => g.SelectionChanged += null).IgnoreArguments();
+            guiMock.Stub(g => g.SelectionChanged -= null).IgnoreArguments();
+            guiMock.Expect(g => g.ProjectOpened += null).IgnoreArguments();
+            guiMock.Stub(g => g.ProjectOpened -= null).IgnoreArguments();
+            guiMock.Expect(g => g.Selection).SetPropertyWithArgument(assessmentSection);
+            guiMock.Expect(g => g.Selection).Return(null);
+            guiMock.Expect(g => g.DocumentViewController).Return(documentViewControllerMock);
+            mockRepository.ReplayAll();
+
+            var project = new RingtoetsProject();
+
+            using (var plugin = new RingtoetsPlugin())
+            {
+                plugin.Gui = guiMock;
+
+                // Call
+                plugin.SetAssessmentSectionToProject(project, assessmentSection);
+            }
+
             // Assert
-            Assert.AreEqual(2, importers.Length);
-            Assert.AreEqual(1, importers.Count(i => i is ReferenceLineImporter));
-            Assert.AreEqual(1, importers.Count(i => i is FailureMechanismSectionsImporter));
+            Assert.AreEqual(1, project.Items.Count);
+            CollectionAssert.Contains(project.Items, assessmentSection);
+            mockRepository.VerifyAll();
         }
 
         [Test]
+        public void SetAssessmentSectionToProject_SelectionAlreadySetToSameAssessmentSection_SelectionNotUpdated()
+        {
+            // Setup
+            var mockRepository = new MockRepository();
+            var assessmentSection = new AssessmentSection(AssessmentSectionComposition.Dike);
+
+            var guiMock = mockRepository.StrictMock<IGui>();
+            guiMock.Stub(g => g.SelectionChanged += null).IgnoreArguments();
+            guiMock.Stub(g => g.SelectionChanged -= null).IgnoreArguments();
+            guiMock.Expect(g => g.ProjectOpened += null).IgnoreArguments();
+            guiMock.Stub(g => g.ProjectOpened -= null).IgnoreArguments();
+
+            guiMock.Expect(g => g.Selection).Return(assessmentSection).Repeat.AtLeastOnce();
+
+            mockRepository.ReplayAll();
+
+            var project = new RingtoetsProject();
+
+            using (var plugin = new RingtoetsPlugin())
+            {
+                plugin.Gui = guiMock;
+
+                // Call
+                plugin.SetAssessmentSectionToProject(project, assessmentSection);
+            }
+
+            // Assert
+            Assert.AreEqual(1, project.Items.Count);
+            CollectionAssert.Contains(project.Items, assessmentSection);
+            mockRepository.VerifyAll();
+        }
+
+        [Test]
+        public void SetAssessmentSectionToProject_SelectionAlreadySetToDifferentAssessmentSection_SelectionUpdated()
+        {
+            // Setup
+            var mockRepository = new MockRepository();
+            var previousAssessmentSection = new AssessmentSection(AssessmentSectionComposition.Dike);
+            var assessmentSection = new AssessmentSection(AssessmentSectionComposition.Dike);
+
+            var documentViewControllerMock = mockRepository.StrictMock<IDocumentViewController>();
+            documentViewControllerMock.Expect(d => d.OpenViewForData(assessmentSection)).Return(true);
+
+            var guiMock = mockRepository.StrictMock<IGui>();
+            guiMock.Stub(g => g.SelectionChanged += null).IgnoreArguments();
+            guiMock.Stub(g => g.SelectionChanged -= null).IgnoreArguments();
+            guiMock.Expect(g => g.ProjectOpened += null).IgnoreArguments();
+            guiMock.Stub(g => g.ProjectOpened -= null).IgnoreArguments();
+            guiMock.Expect(g => g.Selection).SetPropertyWithArgument(assessmentSection);
+            guiMock.Expect(g => g.Selection).Return(previousAssessmentSection).Repeat.AtLeastOnce();
+            guiMock.Expect(g => g.DocumentViewController).Return(documentViewControllerMock);
+            mockRepository.ReplayAll();
+
+            var project = new RingtoetsProject();
+
+            using (var plugin = new RingtoetsPlugin())
+            {
+                plugin.Gui = guiMock;
+
+                // Call
+                plugin.SetAssessmentSectionToProject(project, assessmentSection);
+            }
+
+            // Assert
+            Assert.AreEqual(1, project.Items.Count);
+            CollectionAssert.Contains(project.Items, assessmentSection);
+            mockRepository.VerifyAll();
+        }
+
+        [Test]
         public void WhenAddingAssessmentSection_GivenProjectHasAssessmentSection_ThenAddedAssessmentSectionHasUniqueName()
         {
             // Setup
             var project = new RingtoetsProject();
-            var plugin = new RingtoetsPlugin();
             var assessmentSection1 = new AssessmentSection(AssessmentSectionComposition.Dike);
             var assessmentSection2 = new AssessmentSection(AssessmentSectionComposition.Dike);
-            plugin.SetAssessmentSectionToProject(project, assessmentSection1);
 
-            // Call
-            plugin.SetAssessmentSectionToProject(project, assessmentSection2);
+            using (var plugin = new RingtoetsPlugin())
+            {
+                plugin.SetAssessmentSectionToProject(project, assessmentSection1);
 
+                // Call
+                plugin.SetAssessmentSectionToProject(project, assessmentSection2);
+            }
+
             // Assert
             CollectionAssert.AllItemsAreUnique(project.Items.Select(section => section.Name));
         }