Index: Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/PipingSoilProfileTest.cs
===================================================================
diff -u -rd2b5b334c49948fa49297a1d24c13bc98aa6ee1e -rdc2b06cb5a46cf2508d28fe9a6f8dcaa710346a7
--- Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/PipingSoilProfileTest.cs	(.../PipingSoilProfileTest.cs)	(revision d2b5b334c49948fa49297a1d24c13bc98aa6ee1e)
+++ Ringtoets/Piping/test/Ringtoets.Piping.Data.Test/PipingSoilProfileTest.cs	(.../PipingSoilProfileTest.cs)	(revision dc2b06cb5a46cf2508d28fe9a6f8dcaa710346a7)
@@ -1,46 +1,43 @@
 using System;
+using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.Linq;
+using Core.Common.TestUtil;
 using NUnit.Framework;
 
 namespace Ringtoets.Piping.Data.Test
 {
     public class PipingSoilProfileTest
     {
         [Test]
-        [TestCase(1)]
-        [TestCase(5)]
-        public void Constructor_WithNameBottomLayersAndAquifer_ReturnsInstanceWithPropsAndEquivalentLayerCollection(int layerCount)
+        public void Constructor_WithNameBottomLayersAndAquifer_ReturnsInstanceWithPropsAndEquivalentLayerCollection()
         {
             // Setup
             var name = "Profile";
-            var bottom = new Random(22).NextDouble();
-            var equivalentLayers = new Collection<PipingSoilLayer>();
-            for (var i = 0; i < layerCount; i++)
+            var random = new Random(22);
+            var bottom = random.NextDouble();
+            var layers = new Collection<PipingSoilLayer>
             {
-                equivalentLayers.Add(new PipingSoilLayer(0.0)
-                {
-                    IsAquifer = i == 0
-                });
-            }
+                new PipingSoilLayer(bottom)
+            };
 
             // Call
-            var profile = new PipingSoilProfile(name, bottom, equivalentLayers);
+            var profile = new PipingSoilProfile(name, bottom, layers);
 
             // Assert
-            Assert.AreNotSame(equivalentLayers, profile.Layers);
-            CollectionAssert.AreEqual(equivalentLayers, profile.Layers);
+            Assert.AreNotSame(layers, profile.Layers);
             Assert.AreEqual(name, profile.Name);
             Assert.AreEqual(bottom, profile.Bottom);
         }
+
         [Test]
         public void Constructor_WithNameBottomLayersEmpty_ThrowsArgumentException()
         {
             // Call
             TestDelegate test = () => new PipingSoilProfile(String.Empty, Double.NaN, new Collection<PipingSoilLayer>());
 
             // Assert
-            var message = Assert.Throws<ArgumentException>(test).Message;
-            Assert.AreEqual(Properties.Resources.Error_Cannot_Construct_PipingSoilProfile_Without_Layers, message);
+            TestHelper.AssertThrowsArgumentExceptionAndTestMessage<ArgumentException>(test, Properties.Resources.Error_Cannot_Construct_PipingSoilProfile_Without_Layers);
         }
 
         [Test]
@@ -50,11 +47,96 @@
             TestDelegate test = () => new PipingSoilProfile(String.Empty, Double.NaN, null);
 
             // Assert
-            var message = Assert.Throws<ArgumentNullException>(test).Message;
-            StringAssert.StartsWith(Properties.Resources.Error_Cannot_Construct_PipingSoilProfile_Without_Layers, message);
+            TestHelper.AssertThrowsArgumentExceptionAndTestMessage<ArgumentNullException>(test, Properties.Resources.Error_Cannot_Construct_PipingSoilProfile_Without_Layers);
         }
 
         [Test]
+        [TestCase(1)]
+        [TestCase(5)]
+        [TestCase(15)]
+        public void Layers_Always_ReturnsDescendingByTopOrderedList(int layerCount)
+        {
+            // Setup
+            var random = new Random(21);
+            var bottom = 0.0;
+            var equivalentLayers = new List<PipingSoilLayer>(layerCount);
+            for (var i = 0; i < layerCount; i++)
+            {
+                equivalentLayers.Add(new PipingSoilLayer(random.NextDouble())
+                {
+                    IsAquifer = i == 0
+                });
+            }
+
+            var profile = new PipingSoilProfile(string.Empty, bottom, equivalentLayers);
+
+            // Call
+            var result = profile.Layers.ToArray();
+
+            // Assert
+            CollectionAssert.AreEquivalent(equivalentLayers, result);
+            CollectionAssert.AreEqual(equivalentLayers.OrderByDescending(l => l.Top).Select(l => l.Top), result.Select(l => l.Top));
+        }
+
+        [Test]
+        [TestCase(1e-6)]
+        [TestCase(4)]
+        public void Constructor_WithNameBottomLayersBelowBottom_ThrowsArgumentException(double deltaBelowBottom)
+        {
+            // Setup
+            var bottom = 0.0;
+            var pipingSoilLayers = new[]
+            {
+                new PipingSoilLayer(bottom - deltaBelowBottom),
+                new PipingSoilLayer(1.1)
+            };
+
+            // Call
+            TestDelegate test = () => new PipingSoilProfile(String.Empty, bottom, pipingSoilLayers);
+
+            // Assert
+            TestHelper.AssertThrowsArgumentExceptionAndTestMessage<ArgumentException>(test, "Eén of meerdere lagen hebben een top onder de bodem van het profiel.");
+        }
+
+        [Test]
+        [TestCase(0,0)]
+        [TestCase(1,1.1)]
+        public void GetLayerThickness_LayerInProfile_ReturnsThicknessOfLayer(int layerIndex, double expectedThickness)
+        {
+            // Setup
+            var pipingSoilLayers = new[]
+            {
+                new PipingSoilLayer(0.0),
+                new PipingSoilLayer(1.1)
+            };
+            var profile = new PipingSoilProfile(string.Empty, 0.0, pipingSoilLayers);
+
+            // Call
+            var thickness = profile.GetLayerThickness(pipingSoilLayers[layerIndex]);
+
+            // Assert
+            Assert.AreEqual(expectedThickness, thickness);
+        }
+
+        [Test]
+        public void GetLayerThickness_LayerNotInProfile_ThrowsArgumentException()
+        {
+            // Setup
+            var pipingSoilLayers = new[]
+            {
+                new PipingSoilLayer(0.0),
+                new PipingSoilLayer(1.1)
+            };
+            var profile = new PipingSoilProfile(string.Empty, 0.0, pipingSoilLayers);
+
+            // Call
+           TestDelegate test = () => profile.GetLayerThickness(new PipingSoilLayer(1.1));
+
+            // Assert
+            TestHelper.AssertThrowsArgumentExceptionAndTestMessage<ArgumentException>(test, "Layer not found in profile.");
+        }
+
+        [Test]
         [TestCase(null)]
         [TestCase("")]
         [TestCase("some name")]