package expect

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Module type
Class type

Expect module for testing interactive program.

This is a simple implementation of expect to help building unitary testing of interactive program. Since this is an OCaml library, only specific part of expect has been implemented. Other function can be replaced by standard OCaml functions (exit...).

The use of this library is built around 4 functions:

  • spawn: to create a process
  • send: to send a string to the process
  • expect: match output of the process
  • close: end the process

Output of the program is processed line by line.

Regular expression is implemented through the library Str. You will need to build a regexp using this module. The regexp should only match a substring of the line. If you need to match something at the beginning or at the end, use "^" and "$". To use a regexp

Additional match functions can be build using a standard function. This function is passed the entire line and should return if it match or not.

There is two additional event to match:

  • eof: process close its output
  • timeout: too much time has been spent waiting to match something

Both of this action, if not matched will use the default_action provided.

Here is an example program, that look for string "." in the output:

open Expect

let (), exit_code =
  with_spawn "ls" [|"-alh"|]
  (fun t () ->
    if expect t [`Exact ".", true] false then
      prerr_endline "'.' found"
      prerr_endline "'.' not found")
  match exit_code with
  | Unix.WEXITED 0 ->
      print_endline "Exit normal"
  | _ ->
      print_endline "Problem when exiting"

See Expect manual

  • author Sylvain Le Gall
type t

A process under the monitoring of Expect.

type expect_match = [
  1. | `Eof

    Look for EOF

  2. | `Fun of string -> bool

    Look for a line matching the string

  3. | `Exact of string

    Look for a line matching exactly this string

  4. | `Suffix of string

    Look for a line ending with this string

  5. | `Prefix of string

    Look for a line starting with this string

  6. | `Contains of string

    Look for a line containing this string

  7. | `Timeout

Describe expectation about the output of the process. Lines includes the EOL (i.e. \n).

val spawn : ?verbose:bool -> ?verbose_output:(string -> unit) -> ?timeout:float option -> ?env:string array -> ?use_stderr:bool -> string -> string array -> t

spawn prg args Start a process and monitor its output. Contrary to Unix.create_process, you don't need to repeat the program name at the beginning of args.

Optional parameters:

  • ~timeout: define the default timeout, in seconds. None means that you can wait forever
  • ~env: provide environment to run the process
  • ~use_stderr: redirect stderr to stdout and process it through expect
val set_timeout : t -> float option -> t

Define the timeout for a process.

val send : t -> string -> unit

Send a string to a process.

val expect : t -> ?fmatches:(string -> 'a option) list -> (expect_match * 'a) list -> 'a -> 'a

expect t ~fmatches matches dflt Waits for output of the process and match it against expectations matches. If no expectations match at timeout, returns dflt. You can use ~fmatch to define while processing the output what the result is, if you find a match, return Some res otherwise return None. The function take into account matches before ~fmatch and it picks the first result which is not None.

val close : t -> Unix.process_status

Close the process.

val with_spawn : ?verbose:bool -> ?verbose_output:(string -> unit) -> ?timeout:float option -> ?env:string array -> ?use_stderr:bool -> string -> string array -> (t -> 'a -> 'a) -> 'a -> 'a * Unix.process_status

Take care of opening and closing the process.


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