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Tolerim
23 days ago

How to incorporate testing into a Sequelize migration?

A few months back, I released my application. However, I now have a new idea to enhance its functionality by adding a new column to the table. The database was initiated using the following command:

sequelize.sync()
Although I am familiar with sequelize-cli, I could use the below script:

...
queryInterface.addColumn('Person', 'petName', { type: DataTypes.STRING })
...
The aforementioned solution would have been sufficient if I didn't have to deal with testing as well. I have had to re-initialize the entire database before each test:

beforeEach(async () => {
   await sequelizeConn.sync({ force: true })
})
The combination of migration and testing could've been easily managed if I hadn't used the sync method from the beginning. Is there any way to merge "additional migration" (which only includes minor changes like 'addColumn' and does not initialize the database, like creating tables) with testing? Part of my tests is ensuring that these migrations were performed accurately.

Answers(2)
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Vogi
22 days ago
Verified Answer
Yes, you can use migrations in Sequelize to manage your database schema changes. A Migration in Sequelize is a javascript file which exports two functions, up and down, that dictate how to perform the migration and undo it. You define those functions manually, but you don't call them manually; they will be called automatically by the CLI. You can use migrations to add columns to tables without re-initializing the entire database. You can create a new migration file using the following command:
Then you can add your column using the addColumn method in the up function of the migration file: 
module.exports = {
  up: async (queryInterface, Sequelize) => {
    await queryInterface.addColumn('Person', 'petName', { type: DataTypes.STRING })
  },

  down: async (queryInterface, Sequelize) => {
    await queryInterface.removeColumn('Person', 'petName')
  }
}
You can then run the migration using the following command:
Regarding testing, you can use migrations in combination with testing by creating a separate test database and running your migrations on that database before running your tests. This way you can ensure that your migrations were performed accurately. I hope this helps! Let me know if you have any other questions.

Sources

Migrations | SequelizeMigrations | Sequelizejavascript - Sequelize migration with testing - Stack Overflow
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Tolerim
23 days ago
Yes, you can use sequelize-cli to create a migration file that adds a new column to your table. Here's an example of how you can create a migration file for adding a new column to a table using sequelize-cli: 1. Open the command line in the root directory of your project. 2. Run the following command to create a migration file:
This will create a new migration file in the migrations folder. 3. Edit the migration file to include the code to add a new column to your table: 
module.exports = {
      up: async (queryInterface, Sequelize) => {
        await queryInterface.addColumn('Person', 'petName', {
          type: Sequelize.STRING
        });
      },

      down: async (queryInterface, Sequelize) => {
        await queryInterface.removeColumn('Person', 'petName');
      }
    };
This code will add a new column named petName of type STRING to the Person table. 4. Run the following command to apply the migration to your database:
This will apply the migration to your database and add the new column to your table. 5. You can now run your tests and check if the migration was performed correctly. Note: You can use the sequelize-cli to create many more types of migrations, including changing the data type of a column, dropping a table, and more.
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