elm-test

Write tests in Elm!

Getting Started

Let's start with some example code:

test : Test
test =
    describe "The String module"
        [ describe "String.reverse" -- Nest as many descriptions as you like.
            [ test "has no effect on a palindrome" <|
                \() ->
                    let
                        palindrome =
                            "hannah"
                    in
                        Expect.equal palindrome (String.reverse palindrome)

            -- Expect.equal is designed to be used in pipeline style, like this.
            , test "reverses a known string" <|
                \() ->
                    "ABCDEFG"
                        |> String.reverse
                        |> Expect.equal "GFEDCBA"

            -- fuzz runs the test 100 times with randomly-generated inputs!
            , fuzz string "restores the original string if you run it again" <|
                \randomlyGeneratedString ->
                    randomlyGeneratedString
                        |> String.reverse
                        |> String.reverse
                        |> Expect.equal randomlyGeneratedString
            ]
        ]

This code includes a few common things:

• describe to add a description string to a list of tests
• test to write a unit test
• Expect to determine if a test should pass or fail
• fuzz to run a test several times with randomly-generated inputs.

Check out a more complete example or a large real-world test suite for more.

Running tests locally

There are several ways you can run tests locally:

• from your terminal via npm install -g elm-test
• from your browser
• using a custom runner of your own design

Running tests on CI

Here are some examples of running tests on CI servers:

• travis.yml
• appveyor.yml