const attributes = [
    [sequelize.fn(
      "CONCAT",
      sequelize.fn("YEAR", sequelize.col("createdAt")),
      "-",
      sequelize.fn("MONTH", sequelize.col("createdAt")),
      "-",
      sequelize.fn("DAY", sequelize.col("createdAt")),
    ),
    "test"],
    [sequelize.fn("COUNT", sequelize.col("*")), "count"],
  ];

relult = "2018-11-03": 21

Removed classMethods and instanceMethods options from sequelize.define. Sequelize models are now ES6 classes. You can set class / instance level methods like this