How can I connect twice to db in Cypress tests?

Question

I need to connect to my db (Postgres) twice during autotest - at the beginning to truncate and at the end to select a new note from the table.

I tried to do it using pg-promise, but in the second connection it returns null or undefined (the following error shows after asserting expected and real results - "Target cannot be null or undefined.").

If I don't execute the first connecting (for truncating), the second runs normally and returns new note from table.

Also, if I make Truncate after Select, it gives two different result, depending of whether the table empty or not.

If it is empty, the result is the same error. But if there is some record initially, all becomes ok and test finishes without error.

This is how I make connecting and disconnecting to db:

const pgp = require('pg-promise')();
const postgresConfig = require(require('path').resolve('cypress.json'));

function dbConnection(query, userDefineConnection) {
  const db = pgp(userDefineConnection || postgresConfig.db);
  return db.any(query).finally(db.$pool.end)
  // return db.any(query).finally(pgp.end)
}

/**@type {Cypress.PluginConfig} */
module.exports = (on, config) => {
  on("task", {
    dbQuery: (query) => dbConnection(query.query, query.connection)
  });
}

And this is how I make requests to DB in test:

describe('example to-do app', () => {
  beforeEach(() => {
    cy.task('dbQuery', {'query': 'TRUNCATE TABLE auto_db.public.requests RESTART IDENTITY CASCADE'})
  })

  it('tablist displays class', () => {
    cy.contains('button > span', 'Save').click()

    cy.task('dbQuery', {'query': 'SELECT * FROM auto_db.public.requests'})
      .then(queryResponse => {
        expect(queryResponse[0]).to.deep.contain({
          id: 1,
          author_id: 4,
          type_id: 1,
        })
      })
  })

})

Answer 1

If you look at the implementation for cypress-postgres it's similar but they break up the response/return to fit the call to pgp.end() in between.

Since it sounds like the 1st connection isn't closing, I'd suspect the .finally() call isn't working.

const pgp = require('pg-promise')();
const postgresConfig = require(require('path').resolve('cypress.json'));

function dbConnection(query, userDefineConnection) {
  const db = pgp(userDefineConnection || postgresConfig.db);
  let response = db.any(query)
  pgp.end()
  return response
}

/**@type {Cypress.PluginConfig} */
module.exports = (on, config) => {
  on("task", {
    dbQuery: (query) => dbConnection(query.query, query.connection)
  });
}

You should be able to get rid of the postgresConfig line since (on, config) is the same (in fact it's better because you might want to overwrite some config on the command line).

const pgp = require('pg-promise')();

/**@type {Cypress.PluginConfig} */
module.exports = (on, config) => {

  function dbConnection(query, userDefineConnection) {
    const db = pgp(userDefineConnection || config.db);
    let response = db.any(query)
    pgp.end()
    return response
  }

  on("task", {
    dbQuery: (query) => dbConnection(query.query, query.connection)
  });
}

Answer 2

The problem was that new record in database has been creating not right away and cypress just was looking in db earlier that creating. Adding of waiting before db checking helped.