SequelizeForeignKeyConstraintError - mysql

Question

I'm having problems with associations using Sequelize. I'm trying to create a Task, and it should belong to a User and a Department.
Here is my Task file:
module.exports = function (sequelize, DataTypes) {
var Task = sequelize.define("Task", {
id: {
type: DataTypes.INTEGER,
autoIncrement: true,
primaryKey: true
},
task_name: {
type: DataTypes.STRING,
notNull: true
},
description: {
type: DataTypes.STRING,
notNull: true
},
completed: {
type: DataTypes.BOOLEAN
}
}, {
tableName: 'tasks',
timestamps: false,
});
Task.associate = function (models) {
Task.belongsTo(models.Department, {
onDelete: 'CASCADE',
allowNull: true
});
Task.belongsTo(models.User, {
onDelete: 'CASCADE',
allowNull: true
});
}
return Task;
};
My departments file:
module.exports = function (sequelize, DataTypes) {
var Department = sequelize.define("Department", {
id: {
type: DataTypes.INTEGER,
autoIncrement: true,
primaryKey: true
},
departmentName: DataTypes.STRING,
description: {
type: DataTypes.STRING,
notNull: true
}
}, {
tableName: 'departments',
timestamps: false,
});
Department.associate = function (models) {
Department.belongsTo(models.Project, {
allowNull: true
});
Department.hasMany(models.Task, {
allowNull: true
});
}
return Department;
};
And finally my User file:
const bcrypt = require('bcryptjs');
module.exports = function (sequelize, Sequelize) {
var User = sequelize.define('User', {
id: {
autoIncrement: true,
primaryKey: true,
type: Sequelize.INTEGER
},
fullname: {
type: Sequelize.STRING,
notEmpty: true
},
username: {
type: Sequelize.TEXT
},
email: {
type: Sequelize.STRING,
validate: {
isEmail: true
}
},
password: {
type: Sequelize.STRING,
allowNull: false
},
last_login: {
type: Sequelize.STRING
}
}, {
tableName: 'users',
timestamps: false
});
User.associate = function (models) {
User.hasMany(models.Task, {});
}
User.prototype.validPassword = function (password) {
return bcrypt.compareSync(password, this.password);
};
User.hook("beforeCreate", (instance) => {
if (instance.password) {
instance.password = bcrypt.hashSync(instance.password, bcrypt.genSaltSync(10), null);
}
});
return User;
}
I have googled high and low for an answer to this and I cannot find anything! Help is much appreciated.