Elm BDD API sketch

.gitignore

elm-stuff/

BDD.elm

module BDD exposing (..)

import String
import Expect exposing (Expectation)
import State exposing (State)


type alias Spec a =
    State Trace a


type alias Trace =
    { messages : List String
    , result : Expectation
    }


given : String -> a -> Spec a
given msg x =
    log ("GIVEN " ++ msg) |> andThen (\() -> State.state x)


when : String -> Spec ()
when msg =
    log ("WHEN " ++ msg)


then' : String -> Expectation -> Spec ()
then' msg expectation =
    log ("THEN " ++ msg) |> andThen (assert expectation |> always)


assert : Expectation -> Spec ()
assert expectation =
    State.modify
        <| \({ result } as trace) ->
            result
                |> Expect.getFailure
                |> Maybe.map (always trace)
                |> Maybe.withDefault { trace | result = expectation }


log : String -> Spec ()
log msg =
    State.modify
        <| \({ result, messages } as trace) ->
            case result |> Expect.getFailure of
                Just _ ->
                    trace

                Nothing ->
                    { trace | messages = msg :: messages }


map : (a -> b) -> Spec a -> Spec b
map =
    State.map


andThen : (a -> Spec b) -> Spec a -> Spec b
andThen =
    flip State.andThen


run : Spec a -> Expectation
run spec =
    let
        { messages, result } =
            spec
                |> State.finalState { messages = [], result = Expect.pass }
    in
        result
            |> Expect.getFailure
            |> Maybe.map
                (\{ message } ->
                    messages
                        |> List.reverse
                        |> (::) message
                        |> List.reverse
                        |> String.join "\n"
                        |> Expect.fail
                )
            |> Maybe.withDefault Expect.pass

elm-package.json

{
    "version": "1.0.0",
    "summary": "helpful summary of your project, less than 80 characters",
    "repository": "https://github.com/user/project.git",
    "license": "BSD3",
    "source-directories": [
        "."
    ],
    "exposed-modules": [],
    "dependencies": {
        "elm-community/elm-test": "2.0.1 <= v < 3.0.0",
        "elm-lang/core": "4.0.5 <= v < 5.0.0",
        "folkertdev/elm-state": "1.0.0 <= v < 2.0.0"
    },
    "elm-version": "0.17.0 <= v < 0.18.0"
}