Testing

Use Rata.Fetch.Mock when code needs {Fetch} but tests should not make network requests.

Always return one response

import Rata.Fetch
import Rata.Fetch.Mock

fun check_status : String -> Result Int Fetch.FetchError needs {Fetch.Fetch}
check_status url = case Fetch.get url {
  Ok response -> Ok response.status
  Err error -> Err error
}

fun test_demo () = {
  let mock = Mock.always (Mock.text_response Fetch.status_ok "ok")

  dbg (check_status "https://example.com" with mock)
}

Mock.always is useful when the URL does not matter and the caller only needs some successful response.

Always fail

let mock = Mock.failing Fetch.Timeout

Use this for transport error branches: timeout, DNS failure, TLS failure, unsupported schemes, and backend errors.

Route matching

Routes match by method and exact URL:

let mock =
  Mock.routes [
    Mock.route_response
      Fetch.GET
      "https://example.com/users"
      (Mock.text_response Fetch.status_ok "users"),
    Mock.route_error
      Fetch.POST
      "https://example.com/users"
      Fetch.Timeout,
  ]

Headers and body are not part of route matching in v1. If no route matches, the mock returns BackendError with the method and URL in the message.

Response helpers

pub fun empty_response : Int -> Response
pub fun text_response : Int -> String -> Response
pub fun bytes_response : Int -> List Header -> BitString -> Response

text_response sets content-type: text/plain; charset=utf-8. bytes_response uses exactly the headers and body you provide.