Index: Ringtoets/Common/src/Ringtoets.Common.IO/FileImporters/HydraulicBoundaryDatabaseImporter.cs
===================================================================
diff -u -re182f6f394aa75e739467a77e7bcacd9a8b25429 -r705c72000f0c3e8171ce9494dd31434a3d863f24
--- Ringtoets/Common/src/Ringtoets.Common.IO/FileImporters/HydraulicBoundaryDatabaseImporter.cs	(.../HydraulicBoundaryDatabaseImporter.cs)	(revision e182f6f394aa75e739467a77e7bcacd9a8b25429)
+++ Ringtoets/Common/src/Ringtoets.Common.IO/FileImporters/HydraulicBoundaryDatabaseImporter.cs	(.../HydraulicBoundaryDatabaseImporter.cs)	(revision 705c72000f0c3e8171ce9494dd31434a3d863f24)
@@ -51,6 +51,7 @@
         /// created <see cref="HydraulicBoundaryDatabase"/>.</param>
         /// <param name="filePath">The path of the hydraulic boundary database file to import from.</param>
         /// <returns><c>True</c> if the import was successful, <c>false</c> otherwise.</returns>
+        /// <exception cref="ArgumentNullException">Thrown when <paramref name="targetItem"/> is <c>null</c>.</exception>
         /// <exception cref="CriticalFileReadException">Thrown when:
         /// <list type="bullet">
         /// <item>The given file at <paramref name="filePath"/> cannot be read.</item>
@@ -59,6 +60,10 @@
         /// </exception>
         public bool Import(IAssessmentSection targetItem, string filePath)
         {
+            if (targetItem == null)
+            {
+                throw new ArgumentNullException(nameof(targetItem));
+            }
             ValidateAndConnectTo(filePath);
 
             var hydraulicBoundaryDatabase = targetItem.HydraulicBoundaryDatabase;
Index: Ringtoets/Common/test/Ringtoets.Common.IO.Test/FileImporters/HydraulicBoundaryDatabaseImporterTest.cs
===================================================================
diff -u -r7b85dbce8bcc39e824c367468892764778527ce4 -r705c72000f0c3e8171ce9494dd31434a3d863f24
--- Ringtoets/Common/test/Ringtoets.Common.IO.Test/FileImporters/HydraulicBoundaryDatabaseImporterTest.cs	(.../HydraulicBoundaryDatabaseImporterTest.cs)	(revision 7b85dbce8bcc39e824c367468892764778527ce4)
+++ Ringtoets/Common/test/Ringtoets.Common.IO.Test/FileImporters/HydraulicBoundaryDatabaseImporterTest.cs	(.../HydraulicBoundaryDatabaseImporterTest.cs)	(revision 705c72000f0c3e8171ce9494dd31434a3d863f24)
@@ -65,6 +65,20 @@
         }
 
         [Test]
+        public void Import_AssessmentSectionNull_ThrowsArgumentNullException()
+        {
+            // Setup
+            string validFilePath = Path.Combine(testDataPath, "complete.sqlite");
+
+            // Call
+            TestDelegate test = () => importer.Import(null, validFilePath);
+
+            // Assert
+            string paramName = Assert.Throws<ArgumentNullException>(test).ParamName;
+            Assert.AreEqual("targetItem", paramName);
+        }
+
+        [Test]
         public void Import_ExistingFile_DoesNotThrowException()
         {
             // Setup
Index: Ringtoets/Integration/test/Ringtoets.Integration.TestUtils.Test/DataImportHelperTest.cs
===================================================================
diff -u -r199f41a71b3b4c214f819f4519fffd4dc9418ff9 -r705c72000f0c3e8171ce9494dd31434a3d863f24
--- Ringtoets/Integration/test/Ringtoets.Integration.TestUtils.Test/DataImportHelperTest.cs	(.../DataImportHelperTest.cs)	(revision 199f41a71b3b4c214f819f4519fffd4dc9418ff9)
+++ Ringtoets/Integration/test/Ringtoets.Integration.TestUtils.Test/DataImportHelperTest.cs	(.../DataImportHelperTest.cs)	(revision 705c72000f0c3e8171ce9494dd31434a3d863f24)
@@ -41,9 +41,20 @@
         }
 
         [Test]
-        public void ImportReferenceLine_Always_AddsReferenceLineGeometry()
+        public void ImportReferenceLine_AssesmentSectionNull_ThrowsArgumentNullException()
         {
             // Call
+            TestDelegate test = () => DataImportHelper.ImportReferenceLine(null);
+
+            // Assert
+            string paramName = Assert.Throws<ArgumentNullException>(test).ParamName;
+            Assert.AreEqual("importTarget", paramName);
+        }
+
+        [Test]
+        public void ImportReferenceLine_ValidAssessmentSection_AddsReferenceLineGeometry()
+        {
+            // Call
             DataImportHelper.ImportReferenceLine(dikeSection);
 
             // Assert
@@ -89,7 +100,10 @@
             IFailureMechanism failureMechanism = dikeSection.GetFailureMechanisms().ElementAt(new Random(21).Next(0, 18));
 
             // Call
-            TestDelegate test = () => DataImportHelper.ImportFailureMechanismSections(dikeSection, new [] { failureMechanism });
+            TestDelegate test = () => DataImportHelper.ImportFailureMechanismSections(dikeSection, new[]
+            {
+                failureMechanism
+            });
 
             // Assert
             var exception = Assert.Throws<ArgumentNullException>(test);
@@ -101,13 +115,13 @@
         {
             // Setup
             DataImportHelper.ImportReferenceLine(dikeSection);
-            var failureMechanismCount = 18;
+            const int failureMechanismCount = 18;
             var random = new Random(21);
             var chosenNumbers = new[]
             {
                 random.Next(failureMechanismCount),
                 random.Next(failureMechanismCount),
-                random.Next(failureMechanismCount),
+                random.Next(failureMechanismCount)
             }.Distinct();
             IEnumerable<IFailureMechanism> sectionFailureMechanisms = dikeSection.GetFailureMechanisms().ToArray();
             IEnumerable<IFailureMechanism> failureMechanisms = sectionFailureMechanisms.Where((fm, i) => chosenNumbers.Contains(i));
@@ -125,9 +139,20 @@
         }
 
         [Test]
-        public void ImportHydraulicBoundaryDatabase_Always_AddsFourSurfaceLines()
+        public void ImportHydraulicBoundaryDatabase_AssessmentSectionNull_ThrowsArgumentNullException()
         {
             // Call
+            TestDelegate test = () => DataImportHelper.ImportHydraulicBoundaryDatabase(null);
+
+            // Assert
+            string paramName = Assert.Throws<ArgumentNullException>(test).ParamName;
+            Assert.AreEqual("targetItem", paramName);
+        }
+
+        [Test]
+        public void ImportHydraulicBoundaryDatabase_ValidAssessmentSection_AddsFourSurfaceLines()
+        {
+            // Call
             DataImportHelper.ImportHydraulicBoundaryDatabase(dikeSection);
 
             // Assert
Index: Ringtoets/Integration/test/Ringtoets.Integration.TestUtils.Test/DataUpdateHelperTest.cs
===================================================================
diff -u -r199f41a71b3b4c214f819f4519fffd4dc9418ff9 -r705c72000f0c3e8171ce9494dd31434a3d863f24
--- Ringtoets/Integration/test/Ringtoets.Integration.TestUtils.Test/DataUpdateHelperTest.cs	(.../DataUpdateHelperTest.cs)	(revision 199f41a71b3b4c214f819f4519fffd4dc9418ff9)
+++ Ringtoets/Integration/test/Ringtoets.Integration.TestUtils.Test/DataUpdateHelperTest.cs	(.../DataUpdateHelperTest.cs)	(revision 705c72000f0c3e8171ce9494dd31434a3d863f24)
@@ -38,7 +38,7 @@
         }
 
         [Test]
-        public void ImportPipingStochasticSoilModels_Always_AddsThreeSoilModelsWithProfiles()
+        public void ImportPipingStochasticSoilModels_ValidAssessmentSection_AddsThreeSoilModelsWithProfiles()
         {
             // Call
             DataUpdateHelper.UpdatePipingStochasticSoilModels(dikeSection);