diff --git a/Gu.Xml.Tests/XmlTests.ReferenceLoops.cs b/Gu.Xml.Tests/XmlTests.ReferenceLoops.cs
index 4a72755..fad2dc5 100644
--- a/Gu.Xml.Tests/XmlTests.ReferenceLoops.cs
+++ b/Gu.Xml.Tests/XmlTests.ReferenceLoops.cs
@@ -1,4 +1,5 @@
-namespace Gu.Xml.Tests
+// ReSharper disable UnusedAutoPropertyAccessor.Global
+namespace Gu.Xml.Tests
 {
     using System;
     using NUnit.Framework;
@@ -29,7 +30,7 @@ public void LinkedListRootOneNode()
             }
 
             [Test]
-            public void Infinite()
+            public void LinkedListInfinite()
             {
                 var list = new LinkedList();
                 list.Next = list;
@@ -37,10 +38,49 @@ public void Infinite()
                 Assert.AreEqual("Indent level > 1000, reference loop?", exception.Message);
             }
 
+            [Test]
+            public void ParentNoChild()
+            {
+                var actual = Xml.Serialize(new Parent());
+                var expected = "<?xml version=\"1.0\" encoding=\"utf-8\"?>" + Environment.NewLine +
+                               "<Parent />";
+                Assert.AreEqual(expected, actual);
+            }
+
+            [Test]
+            public void ParentChild()
+            {
+                var actual = Xml.Serialize(new Parent { Child = new Child() });
+                var expected = "<?xml version=\"1.0\" encoding=\"utf-8\"?>" + Environment.NewLine +
+                               "<Parent>" + Environment.NewLine +
+                               "  <Child />" + Environment.NewLine +
+                               "</Parent>";
+                Assert.AreEqual(expected, actual);
+            }
+
+            [Test]
+            public void ParentChildInfinite()
+            {
+                var parent = new Parent { Child = new Child() };
+                parent.Child.Parent = parent;
+                var exception = Assert.Throws<InvalidOperationException>(() => Xml.Serialize(parent));
+                Assert.AreEqual("Indent level > 1000, reference loop?", exception.Message);
+            }
+
             public class LinkedList
             {
                 public LinkedList Next { get; set; }
             }
+
+            public class Parent
+            {
+                public Child Child { get; set; }
+            }
+
+            public class Child
+            {
+                public Parent Parent { get; set; }
+            }
         }
     }
 }
\ No newline at end of file