eunit

Minimalistic unit testing framework for Elm.

Installation

In the root directory of an Elm project:

• Run elm-package install eunit to install the eunit Elm package
• Run npm install -g eunit-runner to install the command line test runner

Creating tests

To generate a test example run eunit init in the root directory of an Elm project to which tests should be added. Test example should be created in test/Main.elm

import Expectation exposing (eql, isTrue)
import Test exposing (it, describe, Test)
import Runner exposing (runAll)

import Html exposing (Html)

all : Test
all = describe "Arithmetic operations"
  [ describe "Addition"
    [ it "should add two positive numbers" <|
        eql (1 + 2) 3
      , it "should be commutative" <|
        eql (1 + 2) (2 + 1)
      , it "should be associative" <|
        eql ((1 + 2) + 3) (1 + (2 + 3))
    ]
    , describe "Multiplication"
    [
      it "should multiply two positive numbers" <|
        eql (2 * 3) 6
      , it "should be commutative" <|
        eql (2 * 3) (3 * 2)
      , it "should be associative" <|
        eql ((2 * 3) * 4) (2 * (3 * 4))
    ]
    , describe "Subtraction"
    [
      it "should subtract two  numbers" <|
        eql (2 - 3) -1
      , it "should be commutative?" <| -- Failing test, subtraction is not commutative!
        eql (2 - 3) (3 - 2)
      , it "should be associative?" <| -- Failing test, subtraction is not associative!
        isTrue (((2 - 3) - 4) == (2 - (3 - 4)))
    ]
  ]

main : Html msg
main =
  runAll all

Test structure should be self-explanatory, it is inspired largely by Jasmine. Some differences:

• Test defined by it can have only one expectation
• Available expectations are only limited to eql, isTrue, isFalse
• There is no beforeEach and afterEach as tests are written for stateless functions and do not require setting up shared state

Running tests

In browser

Tests can be simply run in browser, just start elm-reactor in the root directory of the project and access test/Main.elm. Running tests in a browser can be a good way to debug a particular test failure.

Command line

Make sure that eunit-runner NPM package is installed globally, run eunit in the root directory of the project. You should get an output like the following one:

  EUnit test runner 
 Running test suite... 
 
  Arithmetic operations 
 
  .......xx 
 Elapsed time: 500ms 
 Passed: 7 
 FAILED: 2 
 To debug run 'elm-reactor -p 9908 ' and open http://localhost:9908/test/Main.elm in a browser for more details.