It's something like this

cypress.config.ts

import { defineConfig } from 'cypress';
import { seed } from './cypress/plugins/seed';
import vitePreprocessor from 'cypress-vite';

export default defineConfig({
	video: false,
	e2e: {
		baseUrl: 'http://localhost:5173',

		specPattern: '**/*.cy.ts',

		setupNodeEvents(on, config) {
			on('task', {
				seed: async ({ spec }) => {
					return seed(spec);
				}
			});

			on(
				'file:preprocessor',
				vitePreprocessor({
					configFile: './cypress/vite.config.ts',
					mode: 'development'
				})
			);

			return config;
		}
	}
});

map.cy.ts

// Sample test calling a seed file

describe('Map', () => {

	it('display locations', () => {
		cy
			.task('seed', { spec: 'locations' })
			.visit('/map')
			.get(`[data-cy=marker]`).should('have.length', 10);
	});
});

seed.ts

import { exec } from 'child-process-promise';
import * as fs from 'fs';
import * as path from 'path';

export async function seed(spec: string) {
	const file = new URL(`../fixtures/sql/${spec}.sql`, import.meta.url);
	if (!fs.existsSync(file.pathname)) {
		// file not exists? create a snapshot.
		await exportData(file.pathname);
	}

	if (spec !== 'reset') {
		await seed('reset');
	}

	const command = `psql -U postgres -f ${file.pathname} -d etransport_test`;
	return exec(command);
}

async function exportData(pathname: string) {
	const dir = path.dirname(pathname);
	if (!fs.existsSync(dir)) {
		fs.mkdirSync(dir, { recursive: true });
	}
	const command = `pg_dump --dbname=etransport_test --schema=public --data-only --file=${pathname} --column-inserts --username=postgres --host=localhost --port=5432`;
	console.log(command);
	return exec(command);
}