Index: DamEngine/trunk/src/Deltares.DamEngine.Data.Tests/Geotechnics/SoilProfile2DSurfaceLineHelperTests.cs
===================================================================
diff -u -r7049 -r7057
--- DamEngine/trunk/src/Deltares.DamEngine.Data.Tests/Geotechnics/SoilProfile2DSurfaceLineHelperTests.cs	(.../SoilProfile2DSurfaceLineHelperTests.cs)	(revision 7049)
+++ DamEngine/trunk/src/Deltares.DamEngine.Data.Tests/Geotechnics/SoilProfile2DSurfaceLineHelperTests.cs	(.../SoilProfile2DSurfaceLineHelperTests.cs)	(revision 7057)
@@ -128,7 +128,7 @@
                     GivenZigZagSurfaceLine = FactoryForSurfaceLines.CreateSurfaceLineInZigZag(-50, 13),
                     ExpectedSurfaceCount = 9,
                     // 3 extra surfaces created: 1 below the "zigzag" surface line + 2 on the left side (between Z=60 and 70)
-                    ExpectedFilling1 = FactoryForSoilProfiles.CreatePolygoneSoilLayer2D([
+                    ExpectedFilling1 = FactoryForSoilProfiles.CreatePolygonSoilLayer2D([
                         new Point2D(-50, 13), new Point2D(-30, 15), new Point2D(10, 11), new Point2D(50, 15), new Point2D(70, 13), new Point2D(70, 10), new Point2D(60, 10), new Point2D(0, 10), new Point2D(-20, 10), new Point2D(-50, 10)
                     ], soilFilling, newSoilProfile2D),
                     ExpectedFilling2 = null,
@@ -501,7 +501,7 @@
             7 => FactoryForSoilProfiles.CreatePentagonSoilLayer2D(new Point2D(-10, 0), new Point2D(0, 0), new Point2D(35, 0), new Point2D(35, -15), new Point2D(-10, -15), newSoilProfile2D, soil5),
             _ => null
         };
-        SoilLayer2D expectedSurfaceFilling = FactoryForSoilProfiles.CreatePolygoneSoilLayer2D([
+        SoilLayer2D expectedSurfaceFilling = FactoryForSoilProfiles.CreatePolygonSoilLayer2D([
             new Point2D(-50, 11), surfaceLine.CharacteristicPoints[1].Point, surfaceLine.CharacteristicPoints[2].Point, surfaceLine.CharacteristicPoints[3].Point, new Point2D(xEndSurfaceLine, 11), new Point2D(xEndSurfaceLine, 10), new Point2D(0, 10), new Point2D(-20, 10), new Point2D(-50, 10)
         ], defaultSoil, newSoilProfile2D);
         CheckSoilProfileContainsSoilLayer(newSoilProfile2D, expectedSurface1);
@@ -520,6 +520,57 @@
     }
 
     /// <summary>
+    /// This test reflects the problem found in MWDAM-3279 when creating a new soil profile with a surface line very close to the
+    /// original surface line from the soil profile. 
+    /// </summary>
+    [Test]
+    [TestCase(1, 2, 2)]
+    [TestCase(0.1, 0.2, 2)]
+    [TestCase(0.01, 0.02, 2)]
+    [TestCase(0.007, 0.008, 1)]
+    [TestCase(0.001, 0.002, 1)]
+    public void GivenSoilProfile2DWithSteepOrShallowSlopeInTwoPartsAndSurfaceLineCrossingTheSlope_WhenCombiningWithSurfaceLine_ThenExpectedNewSoilProfile2DCreated(double widthLowestSlope, double widthHighestSlope,int expectedLayerCount)
+    {
+        // Given
+        SoilProfile2D soilProfile2D = FactoryForSoilProfiles.CreateSoilProfile2DWithSteepOrShallowSlopeInTwoParts(widthLowestSlope, widthHighestSlope);
+        var defaultSoil = new Soil("Filling material");
+        GeometryPointString originalSurfaceLine = soilProfile2D.Geometry.SurfaceLine;
+        var surfaceLine = new SurfaceLine2();
+        surfaceLine.Geometry.Points.Add(originalSurfaceLine.Points[0]);
+        surfaceLine.Geometry.Points.Add(originalSurfaceLine.Points[1]);
+        surfaceLine.Geometry.Points.Add(originalSurfaceLine.Points[3]);
+        surfaceLine.Geometry.Points.Add(originalSurfaceLine.Points[4]);
+
+        // When
+        SoilProfile2D newSoilProfile2D = SoilProfile2DSurfaceLineHelper.CombineSurfaceLineWithSoilProfile2D(
+            surfaceLine.Geometry, soilProfile2D, defaultSoil);
+
+        // Then
+        Assert.That(newSoilProfile2D, Is.Not.Null);
+        Assert.That(newSoilProfile2D.Surfaces, Has.Count.EqualTo(expectedLayerCount));
+        var lineNewSurfaceLine = new Line(surfaceLine.Geometry.Points[1], surfaceLine.Geometry.Points[2]);
+        var lineSurfaceSeparation = new Line(new Point2D(widthLowestSlope, -4.15), new Point2D(10, -4.15));
+        var intersectionPoint = new Point2D();
+        Assert.That(LineHelper.DetermineStrictIntersectionPoint(lineNewSurfaceLine, lineSurfaceSeparation, ref intersectionPoint), Is.True);
+
+        if (expectedLayerCount == 2)
+        {
+            var soil1 = new Soil("Surface 1");
+            var soil2 = new Soil("Surface 2");
+            SoilLayer2D expectedSurface1 = FactoryForSoilProfiles.CreatePolygonSoilLayer2D([intersectionPoint, new Point2D(widthLowestSlope + widthHighestSlope, -4.05), new Point2D(10, -4.05), new Point2D(10, -4.15)], soil1, null);
+            SoilLayer2D expectedSurface2 = FactoryForSoilProfiles.CreatePolygonSoilLayer2D([new Point2D(-10, -4.25), new Point2D(0, -4.25), intersectionPoint, new Point2D(10, -4.15), new Point2D(10, -5), new Point2D(-10, -5)], soil2, null);
+            CheckSoilProfileContainsSoilLayer(newSoilProfile2D, expectedSurface1);
+            CheckSoilProfileContainsSoilLayer(newSoilProfile2D, expectedSurface2);
+        }
+
+        if (expectedLayerCount == 1)
+        {
+            // When the surface line is too close to the original surface line, the top surface is not generated.
+            CheckSoilProfileContainsSoilLayer(newSoilProfile2D, soilProfile2D.Surfaces[1]);
+        }
+    }
+
+    /// <summary>
     /// Test case class for GivenSoilProfile2DWhenCombiningWithSurfaceLineThenCorrectNewSoilProfile2DIsCreated()
     /// </summary>
     public class TestCaseSurfaceLine