Index: Application/Ringtoets/src/Application.Ringtoets.Storage/Update/FailureMechanismBaseUpdateExtensions.cs
===================================================================
diff -u -r219f8633c1b5b24f9e9aec3e903734fa94775f0e -r0b923cebc12005d3fec5e5b6830276f1a758928b
--- Application/Ringtoets/src/Application.Ringtoets.Storage/Update/FailureMechanismBaseUpdateExtensions.cs	(.../FailureMechanismBaseUpdateExtensions.cs)	(revision 219f8633c1b5b24f9e9aec3e903734fa94775f0e)
+++ Application/Ringtoets/src/Application.Ringtoets.Storage/Update/FailureMechanismBaseUpdateExtensions.cs	(.../FailureMechanismBaseUpdateExtensions.cs)	(revision 0b923cebc12005d3fec5e5b6830276f1a758928b)
@@ -77,6 +77,17 @@
             }
         }
 
+        /// <summary>
+        /// Gets the <see cref="FailureMechanismEntity"/> based on the <see cref="IFailureMechanism"/>.
+        /// </summary>
+        /// <param name="mechanism">The failure mechanism corresponding with the failure mechanism entity.</param>
+        /// <param name="context">The context to obtain the existing entity from.</param>
+        /// <returns>The stored <see cref="FailureMechanismEntity"/>.</returns>
+        /// <exception cref="EntityNotFoundException">Thrown when either:
+        /// <list type="bullet">
+        /// <item>the <see cref="FailureMechanismEntity"/> couldn't be found in the <paramref name="context"/></item>
+        /// <item>more than one <see cref="FailureMechanismEntity"/> was found in the <paramref name="context"/></item>
+        /// </list></exception>
         internal static FailureMechanismEntity GetSingleFailureMechanism(this IFailureMechanism mechanism, IRingtoetsEntities context)
         {
             try
Index: Application/Ringtoets/test/Application.Ringtoets.Storage.Test/Update/FailureMechanismBaseUpdateExtensionsTest.cs
===================================================================
diff -u -r71123d9c364c97a5ef2eec81acd1bf877a1297b0 -r0b923cebc12005d3fec5e5b6830276f1a758928b
--- Application/Ringtoets/test/Application.Ringtoets.Storage.Test/Update/FailureMechanismBaseUpdateExtensionsTest.cs	(.../FailureMechanismBaseUpdateExtensionsTest.cs)	(revision 71123d9c364c97a5ef2eec81acd1bf877a1297b0)
+++ Application/Ringtoets/test/Application.Ringtoets.Storage.Test/Update/FailureMechanismBaseUpdateExtensionsTest.cs	(.../FailureMechanismBaseUpdateExtensionsTest.cs)	(revision 0b923cebc12005d3fec5e5b6830276f1a758928b)
@@ -24,6 +24,7 @@
 
 using Application.Ringtoets.Storage.Create;
 using Application.Ringtoets.Storage.DbContext;
+using Application.Ringtoets.Storage.Exceptions;
 using Application.Ringtoets.Storage.TestUtil;
 using Application.Ringtoets.Storage.Update;
 using Core.Common.Base.Geometry;
@@ -165,6 +166,81 @@
             Assert.AreEqual(testName, failureMechanismEntity.FailureMechanismSectionEntities.ElementAt(0).Name);
 
             mocks.VerifyAll();
-        } 
+        }
+
+        [Test]
+        public void GetSingleFailureMechanism_ContextWithoutFailureMechanismEntityForId_ThrowsEntityNotFoundException()
+        {
+            // Setup
+            using (RingtoetsEntities ringtoetsEntities = new RingtoetsEntities())
+            {
+                IFailureMechanism failureMechanism = new TestFailureMechanism();
+
+                // Call
+                TestDelegate test = () => failureMechanism.GetSingleFailureMechanism(ringtoetsEntities);
+                
+                // Assert
+                Assert.Throws<EntityNotFoundException>(test);
+            }
+        }
+
+        [Test]
+        public void GetSingleFailureMechanism_ContextWithMultipleFailureMechanismEntityForId_ThrowsEntityNotFoundException()
+        {
+            // Setup
+            MockRepository mocks = new MockRepository();
+            var ringtoetsEntities = RingtoetsEntitiesHelper.Create(mocks);
+            mocks.ReplayAll();
+
+            long testId = new Random(21).Next();
+            var expectedEntity = new FailureMechanismEntity
+            {
+                FailureMechanismEntityId = testId
+            };
+
+            ringtoetsEntities.FailureMechanismEntities.Add(expectedEntity);
+            ringtoetsEntities.FailureMechanismEntities.Add(expectedEntity);
+            IFailureMechanism failureMechanism = new TestFailureMechanism
+            {
+                StorageId = testId
+            };
+
+            // Call
+            TestDelegate test = () => failureMechanism.GetSingleFailureMechanism(ringtoetsEntities);
+
+            // Assert
+            Assert.Throws<EntityNotFoundException>(test);
+
+            mocks.VerifyAll();
+        }
+
+        [Test]
+        public void GetSingleFailureMechanism_ContextWithFailureMechanismEntityForId_ReturnsEntityFromContext()
+        {
+            // Setup
+            MockRepository mocks = new MockRepository();
+            var ringtoetsEntities = RingtoetsEntitiesHelper.Create(mocks);
+            mocks.ReplayAll();
+
+            long testId = new Random(21).Next();
+            var expectedEntity = new FailureMechanismEntity
+            {
+                FailureMechanismEntityId = testId
+            };
+
+            ringtoetsEntities.FailureMechanismEntities.Add(expectedEntity);
+            IFailureMechanism failureMechanism = new TestFailureMechanism
+            {
+                StorageId = testId
+            };
+
+            // Call
+            FailureMechanismEntity entity = failureMechanism.GetSingleFailureMechanism(ringtoetsEntities);
+                
+            // Assert
+            Assert.AreSame(expectedEntity, entity);
+
+            mocks.VerifyAll();
+        }
     }
 }
\ No newline at end of file
Index: Ringtoets/Piping/test/Ringtoets.Piping.Plugin.Test/PipingGuiPluginTest.cs
===================================================================
diff -u -ra61d9a646a09ddee65775c179bba12c40003cf84 -r0b923cebc12005d3fec5e5b6830276f1a758928b
--- Ringtoets/Piping/test/Ringtoets.Piping.Plugin.Test/PipingGuiPluginTest.cs	(.../PipingGuiPluginTest.cs)	(revision a61d9a646a09ddee65775c179bba12c40003cf84)
+++ Ringtoets/Piping/test/Ringtoets.Piping.Plugin.Test/PipingGuiPluginTest.cs	(.../PipingGuiPluginTest.cs)	(revision 0b923cebc12005d3fec5e5b6830276f1a758928b)
@@ -20,7 +20,6 @@
 // All rights reserved.
 
 using System;
-using System.Collections.Generic;
 using System.Linq;
 using Core.Common.Base.Plugin;
 using Core.Common.Controls.TreeView;