CSHARP-767: Added additional unit test that matches scenario described in the JIRA ticket.

Author: rstam

MongoDB.Bson/Serialization/BsonMemberMap.cs

@@ -334,7 +334,7 @@ public BsonMemberMap Reset()
         /// <summary>
         /// Sets the default value creator.
         /// </summary>
-        /// <param name="defaultValueCreator">The default value creator.</param>
+        /// <param name="defaultValueCreator">The default value creator (note: the supplied delegate must be thread safe).</param>
         /// <returns>The member map.</returns>
         public BsonMemberMap SetDefaultValue(Func<object> defaultValueCreator)
         {

MongoDB.BsonUnitTests/Serialization/BsonMemberMapDefaultValueCreatorTests.cs

@@ -48,6 +48,17 @@ public void TestEachDefaultValueIsNewInstance()
             Assert.AreNotSame(c.L, d.L);
         }
 
+        [Test]
+        public void TestModifyingEmptyListDoesNotCorruptDefaultValue()
+        {
+            var json = "{ _id : 1 }";
+            var c1 = BsonSerializer.Deserialize<C>(json);
+            c1.L.Add(1);
+            var c2 = BsonSerializer.Deserialize<C>(json);
+            Assert.AreEqual(1, c1.L.Count);
+            Assert.AreEqual(0, c2.L.Count);
+        }
+
         [Test]
         public void TestValueMissing()
         {