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https://github.com/stoeffel/elm-verify-examples


https://github.com/stoeffel/elm-verify-examples

doctest elm elm-test verify

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# elm-verify-examples [![Build Status](https://travis-ci.org/stoeffel/elm-verify-examples.svg?branch=master)](https://travis-ci.org/stoeffel/elm-verify-examples)



> Verify examples in your docs.



:information_source: This was formerly known as `elm-doc-test`.



:warning: This is not a replacement for tests, this tool should be used for improving your documentation.



## Install



```bash

$ npm i elm-test -g

$ npm i elm-verify-examples -g

$ elm-test init

```



## Setup



There is no need for any configuration. elm-verify-examples will run on all elm files in the specified `source-directories` (`elm.json`). It's possible to create a config file if you want to run it on only a subset of files or on additional markdown files.



```bash

$ touch tests/elm-verify-examples.json

```



`elm-verify-examples.json` contains information on which files contain verified examples and where to find them.



```json

{

  "tests": ["Mock", "Mock.Foo.Bar.Moo", "./README.md"]

}

```



Alternatively you can run elm-verify-examples on all elm files in your source directories:



```json

{

  "tests": "all"

}

```



or



```json

{

  "tests": ["all", "Some.md"]

}

```



It's recommended to add `./tests/VerifyExamples` to your `.gitignore`.



If you are building a _package_, you can pass the string `"exposed"` instead of an explicit list of modules,

this will cause all the documented modules in your package to be verified. This makes it easier to keep these in

sync.



## Writing Verified Examples



Verified examples look like normal code examples in doc-comments. \

Code needs to be indented by 4 spaces.

You can specify the expected result of an expression, by adding a comment `-->` (the `>` is important) and an expected expression.



```elm

{-| returns the sum of two int.



    -- You can write the expected result on the next line,



    add 41 1

    --> 42



    -- or on the same line.



    add 3 3 --> 6



-}



add : Int -> Int -> Int

add =

    (+)

```



### Multiline Examples



You can write examples on multiple lines.



```elm

{-| reverses the list



    rev

        [ 41

        , 1

        ]

    --> [ 1

    --> , 41

    --> ]



    rev [1, 2, 3]

        |> List.map toString

        |> String.concat

    --> "321"



-}



rev : List a -> List a

rev =

    List.reverse

```



### Imports



You can specify imports, if you want to use a module or a special test util.



```elm

{-|



    import Dict



    myWeirdFunc (Dict.fromList [(1, "a"), (2, "b")]) [2, 1]

    --> "ba"



-}

```



### Intermediate Definitions



You can use intermediate definitions in your example.

:information: Unused functions don't get added to the test. This is useful if you wanna add incomplete examples to your docs.

:warning: Intermediate definitions need a type signature!



```elm

{-|



    isEven : Int -> Bool

    isEven n =

        remainderBy 2 n == 0



    List.Extra.filterNot isEven [1,2,3,4] --> [1,3]



-}



filterNot : (a -> Bool) -> List a -> List a

```



### Types in Examples



You can define union types and type aliases in your examples.



```elm

{-| With a union type in the example.

type Animal

= Dog

| Cat



    double Dog

    --> (Dog, Dog)



-}



double : a -> ( a, a )

double a =

    ( a, a )

```



```elm

{-| With a type alias in the example.



    customTypeAlias defaultUser "?"

    --> "?Luke"



    type alias User =

        { id: Int -- ID

        , name: String

        }



    defaultUser : User

    defaultUser =

        { id = 1

        , name = "Luke"

        }



    customTypeAlias defaultUser "_"

    --> "_Luke"



-}



customTypeAlias : { a | name : String } -> String -> String

customTypeAlias { name } prefix =

    prefix ++ name

```



### Examples in markdown files



You can also verify code example in markdown files (such as your README). To do so, add the file's path to your `elm-verify-examples.json` file and write your example using the sames rules as above (no need for 4-space indentation here).



````

This is my README!

It explains how the `Documented` module works:



```elm

import Documented



Documented.two --> 2

```

````



## Verify Examples



`elm-verify-examples` converts your verify-examples into elm-tests, and optionally runs them using `elm-test`. To only generate the test files in `tests/VerifyExamples/`:



```bash

$ elm-verify-examples

```



This is useful if you want to run your tests using different runner than `elm-test`, e.g. `elm-coverage`. If you also want to run the generated tests:



```bash

$ elm-verify-examples --run-tests

```



Note that this way the test files will be removed after they are ran.



By default, this command looks for the config file at `tests/elm-verify-examples.json`. If you want it to load a specific config file use the `--config` argument (e.g. `elm-verify-examples --config my/custom/path/elm-verify-examples.json` will read the config from `my/custom/path/elm-verify-examples.json`).



You can run elm-verify-examples for one or more modules explicitly. They don't have to be specified in `tests/elm-verify-examples.json`.



```bash

$ elm-verify-examples ./src/Foo.elm ./src/Foo/Bar.elm

```



You can pass a custom path to elm-test if necessary.



```bash

$ elm-verify-examples --elm-test=./node_modules/.bin/elm-test

$ # or add it to your elm-verify-examples.json `elmTest: "../node....`

$ # you can also pass arguments to elm-test with --elm-test-args

```



It will use the elm-test installed with this package.