Index: Riskeer/AssemblyTool/src/Riskeer.AssemblyTool.KernelWrapper/Calculators/Assembly/AssessmentSectionAssemblyCalculator.cs
===================================================================
diff -u -r3449f574e011603ca159ccef3d2164ed3c0fd4ff -r9bb4effb0bbb67ac58342e08f78e3e8398e05bb8
--- Riskeer/AssemblyTool/src/Riskeer.AssemblyTool.KernelWrapper/Calculators/Assembly/AssessmentSectionAssemblyCalculator.cs	(.../AssessmentSectionAssemblyCalculator.cs)	(revision 3449f574e011603ca159ccef3d2164ed3c0fd4ff)
+++ Riskeer/AssemblyTool/src/Riskeer.AssemblyTool.KernelWrapper/Calculators/Assembly/AssessmentSectionAssemblyCalculator.cs	(.../AssessmentSectionAssemblyCalculator.cs)	(revision 9bb4effb0bbb67ac58342e08f78e3e8398e05bb8)
@@ -91,6 +91,11 @@
         public IEnumerable<CombinedFailureMechanismSectionAssembly> AssembleCombinedFailureMechanismSections(
             IEnumerable<IEnumerable<CombinedAssemblyFailureMechanismSection>> input, double assessmentSectionLength)
         {
+            if (input == null)
+            {
+                throw new ArgumentNullException(nameof(input));
+            }
+
             try
             {
                 ICommonFailureMechanismSectionAssembler kernel = factory.CreateCombinedFailureMechanismSectionAssemblyKernel();
Index: Riskeer/AssemblyTool/src/Riskeer.AssemblyTool.KernelWrapper/Calculators/Assembly/IAssessmentSectionAssemblyCalculator.cs
===================================================================
diff -u -r882667e55a3e77e2679551c744688950eab842b7 -r9bb4effb0bbb67ac58342e08f78e3e8398e05bb8
--- Riskeer/AssemblyTool/src/Riskeer.AssemblyTool.KernelWrapper/Calculators/Assembly/IAssessmentSectionAssemblyCalculator.cs	(.../IAssessmentSectionAssemblyCalculator.cs)	(revision 882667e55a3e77e2679551c744688950eab842b7)
+++ Riskeer/AssemblyTool/src/Riskeer.AssemblyTool.KernelWrapper/Calculators/Assembly/IAssessmentSectionAssemblyCalculator.cs	(.../IAssessmentSectionAssemblyCalculator.cs)	(revision 9bb4effb0bbb67ac58342e08f78e3e8398e05bb8)
@@ -50,6 +50,7 @@
         /// <param name="input">The collection of failure mechanism section collections to assemble for.</param>
         /// <param name="assessmentSectionLength">The length of the assessment section.</param>
         /// <returns>A collection of <see cref="CombinedFailureMechanismSectionAssembly"/>.</returns>
+        /// <exception cref="ArgumentNullException">Thrown when <paramref name="input"/> is <c>null</c>.</exception>
         /// <exception cref="AssessmentSectionAssemblyCalculatorException">Thrown when
         /// an error occurs while assembling.</exception>
         IEnumerable<CombinedFailureMechanismSectionAssembly> AssembleCombinedFailureMechanismSections(
Index: Riskeer/AssemblyTool/test/Riskeer.AssemblyTool.KernelWrapper.Test/Calculators/Assembly/AssessmentSectionAssemblyCalculatorTest.cs
===================================================================
diff -u -r3449f574e011603ca159ccef3d2164ed3c0fd4ff -r9bb4effb0bbb67ac58342e08f78e3e8398e05bb8
--- Riskeer/AssemblyTool/test/Riskeer.AssemblyTool.KernelWrapper.Test/Calculators/Assembly/AssessmentSectionAssemblyCalculatorTest.cs	(.../AssessmentSectionAssemblyCalculatorTest.cs)	(revision 3449f574e011603ca159ccef3d2164ed3c0fd4ff)
+++ Riskeer/AssemblyTool/test/Riskeer.AssemblyTool.KernelWrapper.Test/Calculators/Assembly/AssessmentSectionAssemblyCalculatorTest.cs	(.../AssessmentSectionAssemblyCalculatorTest.cs)	(revision 9bb4effb0bbb67ac58342e08f78e3e8398e05bb8)
@@ -251,6 +251,24 @@
         }
 
         [Test]
+        public void AssembleCombinedFailureMechanismSections_InputNull_ThrowsArgumentNullException()
+        {
+            // Setup
+            var mocks = new MockRepository();
+            var kernelFactory = mocks.Stub<IAssemblyToolKernelFactory>();
+            mocks.ReplayAll();
+
+            var calculator = new AssessmentSectionAssemblyCalculator(kernelFactory);
+
+            // Call
+            void Call() => calculator.AssembleCombinedFailureMechanismSections(null, double.NaN);
+
+            // Assert
+            var exception = Assert.Throws<ArgumentNullException>(Call);
+            Assert.AreEqual("input", exception.ParamName);
+        }
+
+        [Test]
         public void AssembleCombinedFailureMechanismSections_WithInvalidInput_ThrowsAssessmentSectionAssemblyCalculatorException()
         {
             // Setup
Index: Riskeer/AssemblyTool/test/Riskeer.AssemblyTool.KernelWrapper.Test/Calculators/AssemblyToolCalculatorFactoryTest.cs
===================================================================
diff -u -r00190b5745e366cf2b9977d53401f8182555fe13 -r9bb4effb0bbb67ac58342e08f78e3e8398e05bb8
--- Riskeer/AssemblyTool/test/Riskeer.AssemblyTool.KernelWrapper.Test/Calculators/AssemblyToolCalculatorFactoryTest.cs	(.../AssemblyToolCalculatorFactoryTest.cs)	(revision 00190b5745e366cf2b9977d53401f8182555fe13)
+++ Riskeer/AssemblyTool/test/Riskeer.AssemblyTool.KernelWrapper.Test/Calculators/AssemblyToolCalculatorFactoryTest.cs	(.../AssemblyToolCalculatorFactoryTest.cs)	(revision 9bb4effb0bbb67ac58342e08f78e3e8398e05bb8)
@@ -126,7 +126,7 @@
         }
 
         [Test]
-        public void CreateAssessmentSectionAssemblyCalculator_WithKernelFactory_Returns()
+        public void CreateAssessmentSectionAssemblyCalculator_WithKernelFactory_ReturnsAssessmentSectionAssemblyCalculator()
         {
             // Setup
             IAssemblyToolCalculatorFactory factory = AssemblyToolCalculatorFactory.Instance;
Index: Riskeer/AssemblyTool/test/Riskeer.AssemblyTool.KernelWrapper.TestUtil/CombinedFailureMechanismSectionsInputAssert.cs
===================================================================
diff -u -r20abc90c18fc18a42be226f6104ebf17f3d3756a -r9bb4effb0bbb67ac58342e08f78e3e8398e05bb8
--- Riskeer/AssemblyTool/test/Riskeer.AssemblyTool.KernelWrapper.TestUtil/CombinedFailureMechanismSectionsInputAssert.cs	(.../CombinedFailureMechanismSectionsInputAssert.cs)	(revision 20abc90c18fc18a42be226f6104ebf17f3d3756a)
+++ Riskeer/AssemblyTool/test/Riskeer.AssemblyTool.KernelWrapper.TestUtil/CombinedFailureMechanismSectionsInputAssert.cs	(.../CombinedFailureMechanismSectionsInputAssert.cs)	(revision 9bb4effb0bbb67ac58342e08f78e3e8398e05bb8)
@@ -38,7 +38,7 @@
         /// </summary>
         /// <param name="original">The original collection of <see cref="CombinedAssemblyFailureMechanismSection"/>
         /// collections.</param>
-        /// <param name="actual">The actual collection of <see cref="Assembly.Kernel.Model.FailureMechanismSections.FailureMechanismSectionList"/>.</param>
+        /// <param name="actual">The actual collection of <see cref="FailureMechanismSectionList"/>.</param>
         /// <exception cref="AssertionException">Thrown when <paramref name="actual"/>
         /// is not equal to <paramref name="original"/>.</exception>
         public static void AssertCombinedFailureMechanismInput(IEnumerable<CombinedAssemblyFailureMechanismSection[]> original, IEnumerable<FailureMechanismSectionList> actual)
Index: Riskeer/Common/src/Riskeer.Common.Data/AssemblyTool/AssemblyToolHelper.cs
===================================================================
diff -u -rc975510c82744319cf957dc0018d7abb847ae95b -r9bb4effb0bbb67ac58342e08f78e3e8398e05bb8
--- Riskeer/Common/src/Riskeer.Common.Data/AssemblyTool/AssemblyToolHelper.cs	(.../AssemblyToolHelper.cs)	(revision c975510c82744319cf957dc0018d7abb847ae95b)
+++ Riskeer/Common/src/Riskeer.Common.Data/AssemblyTool/AssemblyToolHelper.cs	(.../AssemblyToolHelper.cs)	(revision 9bb4effb0bbb67ac58342e08f78e3e8398e05bb8)
@@ -68,13 +68,13 @@
         }
 
         /// <summary>
-        /// Assembles the failure path.
+        /// Assembles the failure mechanism.
         /// </summary>
         /// <param name="failureMechanism">The failure mechanism to assemble.</param>
         /// <param name="performSectionAssemblyFunc">The <see cref="Func{T1,TResult}"/> to perform the failure mechanism section assembly.</param>
         /// <param name="failureMechanismN">The n value of the <paramref name="failureMechanism"/>.</param>
         /// <typeparam name="TSectionResult">The type of section result.</typeparam>
-        /// <returns>The failure path probability.</returns>
+        /// <returns>The failure mechanism probability.</returns>
         /// <exception cref="ArgumentNullException">Thrown when <paramref name="failureMechanism"/>
         /// or <paramref name="performSectionAssemblyFunc"/> is <c>null</c>.</exception>
         /// <exception cref="AssemblyException">Thrown when the failure mechanism could not be successfully assembled.</exception>