miragejs: add latency to network requests

I wanted to test how my application would react if one of my endpoints was really slow.

While I could have modified the network settings in Chrome to throttle my speeds or introduce latency, I wanted the rest of the application to run as normal - this was particularly useful as the feature I wanted to test was nested fairly deeply in the app, so I didn’t want to have to wait on slow connections the whole way down and/or turn on/off the latency for each test.

Fortunately, I am using MirageJS to mock my endpoints, and there’s a very convenient options object that can be used to introduce latency. This is the third argument in a post:

import { Response, Server } from "miragejs"
import { EightySixedItemAction } from "../../../src/store"

export function routesForAvailability(server: Server) {
  server.post(
    `expo/menu/availability`,
    ({ db }, request) => {
      // handle request
    },
    {
      timing: 5_000,
    },
  )
}

The documentation is here. This is slightly different from the server response time, which is also configurable.

Note, however, as far as I can tell there’s no way to deterministically vary the timing based on the contents of the request. Ah, well. C’est la vie. At least now I know how to modify the timing on the connection!