For_testing (virtual_dom.virtual_dom.ui_effect.Ui_effect.For

module Svar : sig ... end

You can think of an Svar.t as like an Ivar.t whose purpose is to allow us to implement of_svar below.

val of_svar_fun : ('query -> 'result Svar.t) -> 'query -> 'result t

Create an effect from a function that returns an Svar.t. This is mostly useful in testing, to emulate a 'query -> 'result Deferred.t function that does not return immediately. You may find Query_response_tracker a more convenient interface than using of_svar directly.

module Query_response_tracker : sig ... end

val of_query_response_tracker : 
  ('query, 'result) Query_response_tracker.t ->
  'query ->
  'result t