diff --git a/src/UnitTests/NumberTheoryTests/GcdRelatedTest.cs b/src/UnitTests/NumberTheoryTests/GcdRelatedTest.cs
index b839bb34..caad8985 100644
--- a/src/UnitTests/NumberTheoryTests/GcdRelatedTest.cs
+++ b/src/UnitTests/NumberTheoryTests/GcdRelatedTest.cs
@@ -64,6 +64,21 @@ namespace MathNet.Numerics.UnitTests.NumberTheoryTests
             Assert.AreEqual(1 << 18, IntegerTheory.GreatestCommonDivisor(1 << 18, 1 << 20), "Gcd(1>>18,1<<20)");
         }
 
+        [Test]
+        public void ExtendedGcdHandlesNormalInputCorrectly()
+        {
+            long x, y;
+
+            Assert.AreEqual(3, IntegerTheory.ExtendedGreatestCommonDivisor(6, 15, out x, out y), "Egcd(6,15)");
+            Assert.AreEqual(3, 6 * x + 15 * y, "Egcd(6,15) -> a*x+b*y");
+
+            Assert.AreEqual(3, IntegerTheory.ExtendedGreatestCommonDivisor(-6, 15, out x, out y), "Egcd(-6,15)");
+            Assert.AreEqual(3, -6 * x + 15 * y, "Egcd(-6,15) -> a*x+b*y");
+
+            Assert.AreEqual(3, IntegerTheory.ExtendedGreatestCommonDivisor(-6, -15, out x, out y), "Egcd(-6,-15)");
+            Assert.AreEqual(3, -6 * x + -15 * y, "Egcd(-6,-15) -> a*x+b*y");
+        }
+
         [Test]
         public void ListGcdHandlesNormalInputCorrectly()
         {
@@ -81,6 +96,14 @@ namespace MathNet.Numerics.UnitTests.NumberTheoryTests
             Assert.AreEqual(100, IntegerTheory.GreatestCommonDivisor(-100), "Gcd(-100)");
         }
 
+        [Test]
+        public void ListGcdChecksForNullArguments()
+        {
+            Assert.Throws(
+                typeof (ArgumentNullException),
+                () => IntegerTheory.GreatestCommonDivisor(null));
+        }
+
         [Test]
         public void LcmHandlesNormalInputCorrectly()
         {
@@ -127,5 +150,13 @@ namespace MathNet.Numerics.UnitTests.NumberTheoryTests
             Assert.AreEqual(1, IntegerTheory.LeastCommonMultiple(), "Lcm()");
             Assert.AreEqual(100, IntegerTheory.LeastCommonMultiple(-100), "Lcm(-100)");
         }
+
+        [Test]
+        public void ListLcmChecksForNullArguments()
+        {
+            Assert.Throws(
+                typeof(ArgumentNullException),
+                () => IntegerTheory.LeastCommonMultiple(null));
+        }
     }
 }