    #[test]
    fn string() -> ExpressionNode {
        let source = "\"foo\"";

        assert_eq!(
            source,
            Ok(ExpressionNode {
                id: DUMMY_NODE_ID,
                kind: ExpressionKind::Literal(LiteralNode {
                    symbol: Symbol::intern("foo"),
                    kind: LiteralKind::String,
                }),