Mongoose weirdness

subdoc_test.js

var mongoose = require('mongoose');

mongoose.connect("localhost", "subdoc_test");
var SubDocSchema = new mongoose.Schema({ foo: String, bar: String });

var mapFrom = function(x) { x.foo = x.abc; x.bar = x.xyz; delete x.abc; delete x.xyz; return x; }

var TestSchema = new mongoose.Schema({
    values:
    {
        type: [SubDocSchema],
        set: function(docs) {
            console.log('set: ' + JSON.stringify(docs.map(mapFrom)));
            docs.map(mapFrom);
            return docs;
        }
    }
});

var TestModel = mongoose.model("TestSchema", TestSchema);

TestModel.collection.drop(function(e){ console.log('drop error: ' + e);});

// Setter seemingly called, but no values get saved..?
var test = new TestModel({ values: [ { abc: "foo", xyz: "bar" } ] });

test.save(function(error)
{
    console.log('save error: ' + error);

    TestModel.findOne({}, function(error, doc)
    {
        console.log('findOne error: ' + error);

        // Expect [ { foo: "foo", bar: "bar" } ]
        console.log(doc.values);
        process.exit();
    });
});