Index: Ringtoets/Common/test/Ringtoets.Common.Service.Test/TargetProbabilityCalculationServiceHelperTest.cs
===================================================================
diff -u -r8d14456703e8c6cc42cc5474817c92f9141eb72b -r6d8bf9569d5fbf8b2591b00f5beca9a2fd9572cb
--- Ringtoets/Common/test/Ringtoets.Common.Service.Test/TargetProbabilityCalculationServiceHelperTest.cs	(.../TargetProbabilityCalculationServiceHelperTest.cs)	(revision 8d14456703e8c6cc42cc5474817c92f9141eb72b)
+++ Ringtoets/Common/test/Ringtoets.Common.Service.Test/TargetProbabilityCalculationServiceHelperTest.cs	(.../TargetProbabilityCalculationServiceHelperTest.cs)	(revision 6d8bf9569d5fbf8b2591b00f5beca9a2fd9572cb)
@@ -84,6 +84,21 @@
             Assert.AreEqual("Doelkans is te groot om een berekening uit te kunnen voeren.", logMessage);
         }
 
+        [Test]
+        [TestCaseSource(nameof(TargetProbabilitiesThatAreTooSmall))]
+        public void ValidateTargetProbability_TargetProbabilityTooSmall_ReturnsFalseAndHandlesExpectedLogMessage(double targetProbability)
+        {
+            // Setup
+            string logMessage = string.Empty;
+
+            // Call
+            bool isValid = TargetProbabilityCalculationServiceHelper.ValidateTargetProbability(targetProbability, lm => logMessage = lm);
+
+            // Assert
+            Assert.IsFalse(isValid);
+            Assert.AreEqual("Doelkans is te klein om een berekening uit te kunnen voeren.", logMessage);
+        }
+
         private static IEnumerable<TestCaseData> ValidTargetProbabilities()
         {
             yield return new TestCaseData(0.005);
@@ -95,5 +110,11 @@
             yield return new TestCaseData(StatisticsConverter.ReliabilityToProbability(-1.005));
             yield return new TestCaseData(5.0);
         }
+
+        private static IEnumerable<TestCaseData> TargetProbabilitiesThatAreTooSmall()
+        {
+            yield return new TestCaseData(StatisticsConverter.ReliabilityToProbability(40.005));
+            yield return new TestCaseData(0.0);
+        }
     }
 }
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