Index: test/Plugins/Wti/Wti.Service.Test/PipingCalculationServiceTest.cs
===================================================================
diff -u -r1689206627a4343d07fafcebb0a931b7a0e9e2d2 -r49b7320ad56bfa60788e8792b79dd537318f68ff
--- test/Plugins/Wti/Wti.Service.Test/PipingCalculationServiceTest.cs	(.../PipingCalculationServiceTest.cs)	(revision 1689206627a4343d07fafcebb0a931b7a0e9e2d2)
+++ test/Plugins/Wti/Wti.Service.Test/PipingCalculationServiceTest.cs	(.../PipingCalculationServiceTest.cs)	(revision 49b7320ad56bfa60788e8792b79dd537318f68ff)
@@ -1,58 +1,104 @@
 using NUnit.Framework;
-using Wti.Calculation.Piping;
+using Rhino.Mocks;
+using Wti.Calculation.Test.Piping.Stub;
 using Wti.Data;
 
 namespace Wti.Service.Test
 {
     public class PipingCalculationServiceTest
     {
-        private readonly PipingData validPipingData = new PipingData
+        private PipingData validPipingData;
+
+        [SetUp]
+        public void SetUp()
         {
-            AssessmentLevel = 1.0,
-            BeddingAngle = 1.0,
-            CriticalHeaveGradient = 1.0,
-            DampingFactorExit = 1.0,
-            DarcyPermeability = 1.0,
-            Diameter70 = 1.0,
-            ExitPointXCoordinate = 1.0,
-            Gravity = 1.0,
-            MeanDiameter70 = 1.0,
-            PiezometricHeadExit = 1.0,
-            PiezometricHeadPolder = 1.0,
-            PhreaticLevelExit = 2.0,
-            SandParticlesVolumicWeight = 1.0,
-            SeepageLength = 1.0,
-            SellmeijerModelFactor = 1.0,
-            SellmeijerReductionFactor = 1.0,
-            ThicknessAquiferLayer = 1.0,
-            ThicknessCoverageLayer = 1.0,
-            UpliftModelFactor = 1.0,
-            WaterKinematicViscosity = 1.0,
-            WaterVolumetricWeight = 1.0,
-            WhitesDragCoefficient = 1.0
-        };
+            validPipingData = new PipingData
+            {
+                AssessmentLevel = 1.0,
+                BeddingAngle = 1.0,
+                CriticalHeaveGradient = 1.0,
+                DampingFactorExit = 1.0,
+                DarcyPermeability = 1.0,
+                Diameter70 = 1.0,
+                ExitPointXCoordinate = 1.0,
+                Gravity = 1.0,
+                MeanDiameter70 = 1.0,
+                PiezometricHeadExit = 1.0,
+                PiezometricHeadPolder = 1.0,
+                PhreaticLevelExit = 2.0,
+                SandParticlesVolumicWeight = 1.0,
+                SeepageLength = 1.0,
+                SellmeijerModelFactor = 1.0,
+                SellmeijerReductionFactor = 1.0,
+                ThicknessAquiferLayer = 1.0,
+                ThicknessCoverageLayer = 1.0,
+                UpliftModelFactor = 1.0,
+                WaterKinematicViscosity = 1.0,
+                WaterVolumetricWeight = 1.0,
+                WhitesDragCoefficient = 1.0
+            };
+        }
 
         [Test]
-        public void Calculate_ValidPipingData_ShouldSetOutput()
+        public void PerfromValidatedCalculation_ValidPipingDataNoOutput_ShouldSetOutput()
         {
+            // Precondition
+            Assert.IsNull(validPipingData.Output);
+
             // Call
-            PipingCalculationService.PerfromValidatedCalculation(validPipingData);
+            var result = PipingCalculationService.PerfromValidatedCalculation(validPipingData);
 
             // Assert
+            Assert.AreEqual(PipingCalculationResult.Successful, result);
             Assert.NotNull(validPipingData.Output);
         }
 
         [Test]
-        public void Calculate_InValidPipingData_ReturnsErrorMessages()
+        public void PerfromValidatedCalculation_ValidPipingDataWithOutput_ShouldChangeOutput()
         {
             // Setup
-            var invalidPipingData = new PipingData();
+            var output = new TestPipingOutput();
+            validPipingData.Output = output;
 
             // Call
-            var results = PipingCalculationService.PerfromValidatedCalculation(invalidPipingData);
+            var result = PipingCalculationService.PerfromValidatedCalculation(validPipingData);
+
+            // Assert
+            Assert.AreEqual(PipingCalculationResult.Successful, result);
+            Assert.AreNotSame(output, validPipingData.Output);
+        }
+
+        [Test]
+        public void PerfromValidatedCalculation_InValidPipingDataWithOutput_ReturnsFalseNoOutputChange()
+        {
+            // Setup
+            var output = new TestPipingOutput();
+            var invalidPipingData = new PipingData
+            {
+                Output = output
+            };
+
+            // Call
+            var result = PipingCalculationService.PerfromValidatedCalculation(invalidPipingData);
             
             // Assert
-            CollectionAssert.IsNotEmpty(results);
+            Assert.AreEqual(PipingCalculationResult.ValidationErrors, result);
+            Assert.AreSame(output, invalidPipingData.Output);
         }
+
+        [Test]
+        public void PerformValidatedCalculation_Diameter70AndAquiferPermeabilityZero_CalculationErrorOutputNull()
+        {
+            // Setup
+            validPipingData.Diameter70 = 0;
+            validPipingData.DarcyPermeability = 0;
+
+            // Call
+            var result = PipingCalculationService.PerfromValidatedCalculation(validPipingData);
+
+            // Assert
+            Assert.AreEqual(PipingCalculationResult.CalculationErrors, result);
+            Assert.Null(validPipingData.Output);
+        }
     }
 }
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