Nuxt/test/fixtures/module/modules/template/index.js

const path = require('path')

module.exports = function () {
    // Disable parsing pages/
    this.nuxt.options.build.createRoutes = () => {}
    // Add /api endpoint
    this.addTemplate({
        fileName: 'router.js',
        src: path.resolve(this.options.srcDir, 'router.js')
    })
}