Wrapping a unit test in a transaction for easy cleanup with Knex.js

knex.js

#!/usr/bin/node
const Promise = require('bluebird')
const config  = require('./config.json')
const knex    = require('./lib/knex')(config.database).connection()


const mock = () => ({ user_id: Math.floor(Math.random() * 999) + 1, payload_type: 'foo', attributes: JSON.stringify({}) })


const before = (t) => {
    console.log('before')
    const tmp = {}
    const p = new Promise( (resolve, reject) => tmp.resolve = resolve )
    knex.transaction( tx => { t.tx = tx; tmp.resolve() } ).catch( () => {} )
    return p
}

const test = async (t) => {
    console.log('test')
    let m1 = mock(), m2 = mock()
    await t.tx('notifications').insert(m1)
    await t.tx('notifications').insert(m2)
}

const after = (t) => {
    console.log('after')
//    return t.tx.commit()
    return t.tx.rollback()
}


let t = {}
             before(t)
.then( () => test(t)  )
.then( () => after(t) )
.catch( e => console.log(`e: ${e}`) )

for ava, we can write like this:

test.beforeEach(test => {
  return new Promise(resolve => {
    knex.transaction(function(t) {
        test.context.transaction = t;

        resolve();

        return new Promise(() => {});
      })
      .catch(() => {});  //why things not working if remove this line? 
  });
});

test.afterEach(async test => {
  await test.context.transaction.rollback();
});

I'm just not sure why things will be not working if we removed the empty catch block. any ideas?

catch(() => {}); //why things not working if remove this line?

knex turns the rollback into an exception which then fails the ava test