public void TestTwoNestedDecimal128s()
 {
     var document = new BsonDocument();
     using (var writer = new BsonDocumentWriter(document))
     {
         writer.WriteStartDocument();
         writer.WriteStartDocument("nested");
         writer.WriteDecimal128("a", (Decimal128)1.5M);
         writer.WriteDecimal128("b", (Decimal128)2.5M);
         writer.WriteEndDocument();
         writer.WriteEndDocument();
     }
     var json = document.ToJson();
     var expected = "{ 'nested' : { 'a' : NumberDecimal('1.5'), 'b' : NumberDecimal('2.5') } }".Replace("'", "\"");
     Assert.Equal(expected, json);
 }