A patch to handle Write-Only properties in WritePropertiesToString<T>. Are write only properties a good idea? I don't know. Did I find one in legacy code? Yes. Did I write that legacy code? Yes.

WriteOnlyProperty.patch

Index: ApprovalUtilities.Tests/Utilities/StringUtilitiesTest.cs
===================================================================
--- ApprovalUtilities.Tests/Utilities/StringUtilitiesTest.cs	(revision 408)
+++ ApprovalUtilities.Tests/Utilities/StringUtilitiesTest.cs	(working copy)
@@ -26,12 +26,34 @@
         [TestMethod]
         public void WritePropertiesToStringTest()
         {
-            var anonymous = new 
+            var anonymous = new
             {
                 SomeString = "Hello",
                 SomeInt = 10
             };
             Approvals.Verify(anonymous.WritePropertiesToString());
         }
+
+        [TestMethod]
+        public void WriteOnlyPropertyTest()
+        {
+            var target = new TestingObject() { WriteOnlyString = "Hello", ReadWriteInt = 10 };
+            Approvals.Verify(target.WritePropertiesToString());
+        }
+
+        public class TestingObject
+        {
+            private string _WriteOnlyString;
+
+            public string WriteOnlyString
+            {
+                set
+                {
+                    _WriteOnlyString = value;
+                }
+            }
+
+            public int ReadWriteInt { get; set; }
+        }
     }
-}
+}
\ No newline at end of file
Index: ApprovalUtilities.Tests/Utilities/StringUtilitiesTest.WriteOnlyPropertyTest.approved.txt
===================================================================
--- ApprovalUtilities.Tests/Utilities/StringUtilitiesTest.WriteOnlyPropertyTest.approved.txt	(revision 0)
+++ ApprovalUtilities.Tests/Utilities/StringUtilitiesTest.WriteOnlyPropertyTest.approved.txt	(working copy)
@@ -0,0 +1,4 @@
+TestingObject
+{
+	ReadWriteInt: 10
+}
Index: ApprovalUtilities/Utilities/StringUtils.cs
===================================================================
--- ApprovalUtilities/Utilities/StringUtils.cs	(revision 408)
+++ ApprovalUtilities/Utilities/StringUtils.cs	(working copy)
@@ -1,7 +1,7 @@
 using System;
 using System.Collections;
+using System.Collections.Generic;
 using System.Text;
-using System.Collections.Generic;
 
 namespace ApprovalUtilities.Utilities
 {
@@ -107,15 +107,19 @@
 
             Type t = typeof(T);
             var sb = new StringBuilder();
-            sb.Append(t.Name + "\r\n{\r\n");
+            sb.AppendLine(t.Name);
+            sb.AppendLine("{");
             foreach (var p in t.GetProperties())
             {
-                var propertyValue = p.GetValue(value, new object[0]) ?? "NULL";
-                sb.AppendFormat("\t{0}: {1}", p.Name, propertyValue).AppendLine();
+                if (p.CanRead)
+                {
+                    var propertyValue = p.GetValue(value, new object[0]) ?? "NULL";
+                    sb.AppendFormat("\t{0}: {1}", p.Name, propertyValue).AppendLine();
+                }
             }
-            sb.Append("}\r\n");
 
+            sb.AppendLine("}");
             return sb.ToString();
         }
-	}
+    }
 }
\ No newline at end of file