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A test framework for asynchronous Elm code.
version 3.0.0
license MIT
native-modules False
elm-version 0.18.0 <= v < 0.19.0
Tag 3.0.0
Committed At 2017-02-17 01:58:07 UTC
elm-lang/core 5.0.0 <= v < 6.0.0 5.1.1



Build Status

Arborist is a test framework for asynchronous Elm code.

It is intended for use mostly with Tasks. Tests are defined as assertions on tasks, which are executed in parallel and reported on the command line.


You'll need to install Node.js (which is used for running the tests), and the Elm Platform.

Once you have both of those, you can install the package:

elm package install SamirTalwar/arborist

The latest version of Arborist is v1.0.0.

Writing tests

Define a test file as follows, with your own test cases.

module My.Wonderful.Tests exposing (tests)

import Arborist.Framework exposing (..)
import Arborist.Matchers exposing (..)
import Process
import Task

tests : List Test
tests =
    test "performs simple equality checks" (
        a = True |> Task.succeed
        b = True |> Task.succeed
        assert a (equals b)

    test "negates matchers" (
        a = True |> Task.succeed
        b = False |> Task.succeed
        assert a (not_ (equals b))

    test "verifies that an integer is between two others" (
      assert (Task.succeed 88) (isIntBetween (Task.succeed 77) (Task.succeed 99))

    test "waits for tasks to succeed" (
        a = Process.sleep 100 |> Task.andThen (always (Task.succeed 42))
        b = Task.succeed 42
        assert a (equals b)

    test "waits for tasks to fail" (
        a = Process.sleep 100 |> Task.andThen (always ( "Well, that didn't work."))
        b = "Well, that didn't work."
        assert (assert a (equals b)) fails

You'll probably find yourself extracting groups of tests out into files as you need. run just takes a list of Test values, so you can concatenate multiple lists of tests with List.concat.

There are a few matchers in Arborist:

  • equals
  • not_
  • isIntBetween

Please submit issues and pull requests with ideas for more!

Running tests

You'll need to use node to run the tests as follows:

node ./elm-stuff/packages/SamirTalwar/arborist/1.0.0/bin/run My.Wonderful.Tests.tests test/Tests.elm

Arborist compiles the test files for you using elm make, so you don't need to add them to your "source-directories" section of elm-package.json.

As you add more test files, you just need to add them to the end of that command line.


Arborist is bound by the Contributor Covenant. Please raise issues and send pull requests.


Arborist is licenced under the MIT License.