Module `Alcotest`

A lightweight and colourful test framework.

Alcotest provides a simple interface to perform unit tests. It exposes a simple TESTABLE module type, a check function to assert test predicates and a run function to perform a list of unit -> unit test callbacks.

From these descriptions, Alcotest builds a quiet and colorful output where only faulty runs are fully displayed at the end of the run (with the full logs ready to inspect), with a simple (yet expressive) query language to select the tests to run.

Release 0.8.5

type speed_level = [ | `Quick | `Slow ]: Speed level of a test. Tests marked as `Quick are always run. Tests marked as `Slow are skipped when the `-q` flag is passed.

type 'a test_case = string * speed_level * ('a -> unit): A test case is an UTF-8 encoded documentation string, a speed level and a function to execute. Typically, the testing function calls the helper functions provided below (such as check and fail).

val test_case : string -> speed_level -> ('a -> unit) -> 'a test_case: test_case n s f is the test case n running at speed s using the function f.

type 'a test = string * 'a test_case list: A test is an US-ASCII encoded name and a list of test cases. * The name can be used for filtering which tests to run on the CLI

exception Test_error: The exception return by run in case of errors.

val run : ?⁠and_exit:bool -> ?⁠argv:string array -> string -> unit test list -> unit

run n t runs the test suite t. n is the name of the tested library.

The optional argument and_exit controls what happens when the function ends. By default, and_exit is set, which makes the function exit with 0 if everything is fine or 1 if there is an issue. If and_exit is false, then the function raises Test_error on error.

The optional argument argv specifies the argument sent to alcotest like "--json", "--verbose", etc. (at least one argument is required).

val run_with_args : ?⁠and_exit:bool -> ?⁠argv:string array -> string -> 'a Cmdliner.Term.t -> 'a test list -> unit: run_with_args n a t Similar to run a t but take an extra argument a. Every test function will receive as arguement the evaluation of the Cdmliner term a: this is useful to configure the test behaviors using the CLI.

Assert functions

module type TESTABLE = sig ... end: TESTABLE provides an abstract description for testable values.

type 'a testable = (module TESTABLE with type t = 'a): The type for testable values.

val testable : 'a Fmt.t -> ('a -> 'a -> bool) -> 'a testable: testable pp eq is a new testable with the pretty-printer pp and equality eq.

val pp : 'a testable -> 'a Fmt.t: pp t is t's pretty-printer.

val equal : 'a testable -> 'a -> 'a -> bool: equal t is t's equality.

val bool : bool testable: bool tests booleans.

val int : int testable: int tests integers.

val int32 : int32 testable: int32 tests 32-bit integers.

val int64 : int64 testable: int64 tests 64-bit integers.

val float : float -> float testable: float tests floats with specified absolute error.

val char : char testable: char tests characters.

val string : string testable: string tests OCaml strings.

val unit : unit testable: unit tests unit values (useful for functions with side-effects).

val list : 'a testable -> 'a list testable: list t tests lists of ts.

val slist : 'a testable -> ('a -> 'a -> int) -> 'a list testable: slist t comp tests sorted lists of ts. The list are sorted using comp.

val array : 'a testable -> 'a array testable: array t tests arrays of ts.

val option : 'a testable -> 'a option testable: option t tests optional ts.

val result : 'a testable -> 'e testable -> ('a, 'e) Result.result testable: result t e tests ts on success and es on failure.

val pair : 'a testable -> 'b testable -> ('a * 'b) testable: pair a b tests pairs of as and bs.

val of_pp : 'a Fmt.t -> 'a testable: of_pp pp tests values which can be printed using pp and compared using Pervasives.compare

val pass : 'a testable: pass tests values of any type and always succeeds.

val reject : 'a testable: reject tests values of any type and always fails.

val check : 'a testable -> string -> 'a -> 'a -> unit: Check that two values are equal.

val fail : string -> 'a: Simply fail.

val failf : ('a, Stdlib.Format.formatter, unit, 'b) Stdlib.format4 -> 'a: Simply fail with a formatted message.

val neg : 'a testable -> 'a testable: neg t is t's negation: it is true when t is false and it is false when t is true.

val check_raises : string -> exn -> (unit -> unit) -> unit: Check that an exception is raised.

Deprecated

val line : Stdlib.out_channel -> ?⁠color:[ `Blue | `Yellow ] -> char -> unit

deprecated

You should write your own line function. For instance:

let line ppf ?color c =
  let line = String.v ~len:terminal_columns (fun _ -> c) in
  match color with
  | Some c -> Fmt.pf ppf "%a\n%!" Fmt.(styled c string)  line
  | None   -> Fmt.pf ppf "%s\n%!"line