public void setField(String name, String value) {
        validateField(name, value);
        objectMap.put(name, new ConfigPayloadBuilder(value));
    }
@Test
    public void require_that_simple_fields_can_be_overwritten() {
        ConfigPayloadBuilder builder = new ConfigPayloadBuilder();
        builder.setField("foo", "bar");
        builder.setField("foo", "baz");
        Cursor root = createSlime(builder);
        // XXX: Not sure if this is the _right_ behavior.
        assertEquals("baz", root.field("foo").asString());
    }