Wallaby

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Wallaby helps you test your web applications by simulating realistic user interactions. By default it runs each test case concurrently and manages browsers for you. Here’s an example test for a simple Todo application:

defmodule MyApp.Features.TodoTest do
  use MyApp.FeatureCase, async: true

  import Wallaby.Query, only: [css: 2, text_field: 1, button: 1]

  test "users can create todos", %{session: session} do
    session
    |> visit("/todos")
    |> fill_in(text_field("New Todo"), with: "Write my first Wallaby test")
    |> click(button("Save"))
    |> assert_has(css(".alert", text: "You created a todo"))
    |> assert_has(css(".todo-list > .todo, text: "Write my first Wallaby test"))
  end
end

Because Wallaby manages multiple browsers for you, its possible to test several users interacting with a page simultaneously.

defmodule MyApp.Features.MultipleUsersTest do
  use MyApp.FeatureCase, async: true

  import Wallaby.Query, only: [text_field: 1, button: 1, css: 2]

  @page message_path(Endpoint, :index)
  @message_field text_field("Share Message")
  @share_button button("Share")

  def message(msg), do: css(".messages > .message", text: msg)

  test "That users can send messages to each other" do
    {:ok, user1} = Wallaby.start_session
    user1
    |> visit(@page)
    |> fill_in(@message_field, with: "Hello there!")
    |> click(@share_button)

    {:ok, user2} = Wallaby.start_session
    user2
    |> visit(@page)
    |> fill_in(@message_field, with: "Hello yourself")
    |> click(@share_button)

    user1
    |> assert_has(message("Hello yourself"))

    user2
    |> assert_has(message("Hello there!"))
  end
end

Read on to see what else Wallaby can do or check out the Official Documentation.

Setup

Add Wallaby to your list of dependencies in mix.exs:

def deps do
  [{:wallaby, "~> 0.17.0"}]
end

Then ensure that Wallaby is started in your test_helper.exs:

{:ok, _} = Application.ensure_all_started(:wallaby)

Phoenix

If you’re testing a Phoenix application with Ecto 2.0 and a database that supports sandbox mode then you can enable concurrent testing by adding the Phoenix.Ecto.SQL.Sandbox plug to your Endpoint. It’s important that this is at the top of endpoint.ex before any other plugs.

# lib/endpoint.ex

defmodule YourApp.Endpoint do
  use Phoenix.Endpoint, otp_app: :your_app

  if Application.get_env(:your_app, :sql_sandbox) do
    plug Phoenix.Ecto.SQL.Sandbox
  end

Make sure Phoenix is set up to serve endpoints and that the SQL sandbox is enabled:

# config/test.exs

config :your_app, YourApplication.Endpoint,
  server: true

config :your_app, :sql_sandbox, true

Then in your test_helper.exs you can provide some configuration to Wallaby. At minimum, you need to specify a :base_url, so Wallaby knows how to resolve relative paths.

# test/test_helper.exs

Application.put_env(:wallaby, :base_url, YourApplication.Endpoint.url)

PhantomJS

Wallaby requires PhantomJS. You can install PhantomJS through NPM or your package manager of choice:

$ npm install -g phantomjs-prebuilt

Wallaby will use whatever PhantomJS you have installed in your path. If you need to specify a specific PhantomJS you can pass the path in the configuration:

config :wallaby, phantomjs: "some/path/to/phantomjs"

You can also pass arguments to PhantomJS through the phantomjs_args config setting, e.g.:

config :wallaby, phantomjs_args: "--webdriver-logfile=phantomjs.log"

Writing tests

It’s easiest to add Wallaby to your test suite by creating a new case template:

defmodule YourApp.FeatureCase do
  use ExUnit.CaseTemplate

  using do
    quote do
      use Wallaby.DSL

      alias YourApp.Repo
      import Ecto
      import Ecto.Changeset
      import Ecto.Query

      import YourApp.Router.Helpers
    end
  end

  setup tags do
    :ok = Ecto.Adapters.SQL.Sandbox.checkout(YourApp.Repo)

    unless tags[:async] do
      Ecto.Adapters.SQL.Sandbox.mode(YourApp.Repo, {:shared, self()})
    end

    metadata = Phoenix.Ecto.SQL.Sandbox.metadata_for(YourApp.Repo, self())
    {:ok, session} = Wallaby.start_session(metadata: metadata)
    {:ok, session: session}
  end
end

Then you can write tests like so:

defmodule YourApp.UserListTest do
  use YourApp.FeatureCase, async: true

  import Wallaby.Query, only: [css: 2]

  test "users have names", %{session: session} do
    session
    |> visit("/users")
    |> find(css(".user", count: 3))
    |> List.first()
    |> assert_has(css(".user-name", text: "Chris"))
  end
end

API

The full documentation for the DSL is in the official documentation.

Queries and Actions

Wallaby’s API is broken into 2 concepts: Queries and Actions.

Queries allow us to declaritively describe the elements that we would like to interact with and Actions allow us to use those queries to interact with the DOM.

Lets say that our html looks like this:

<ul class=".users">
  <li class="user">
    <span class="user-name">Ada</span>
  </li>
  <li class="user">
    <span class="user-name">Grace</span>
  </li>
  <li class="user">
    <span class="user-name">Alan</span>
  </li>
</ul>

If we wanted to interact with all of the users then we could write a query like so css(".user", count: 3). If we only wanted to interact with a specific user then we could write a query like this css(".user-name", count: 1, text: "Ada"). Now we can use those queries with some actions:

session
|> find(css(".user", count: 3))
|> List.first
|> assert_has(css(".user-name", count: 1, text: "Ada"))

There are several queries for common html elements defined in the Query module. All actions accept a query. This makes it easy to use queries we’ve already defined. Actions will block until the query is either satisfied or the action times out. Blocking reduces race conditions when elements are added or removed dynamically.

Navigation

We can navigate directly to pages with visit:

visit(session, "/page.html")
visit(session, user_path(Endpoint, :index, 17))

It’s also possible to click links directly:

click(session, link("Page 1"))

Finding

We can find a specific element or list of elements with find:

@user_form   css(".user-form")
@name_field  text_field("Name")
@email_field text_field("Email")
@save_button button("Save")

find(page, @user_form, fn(form) ->
  form
  |> fill_in(@name_field, with: "Chris")
  |> fill_in(@email_field, with: "c@keathley.io")
  |> click(@save_button)
end)

Passing a callback to find will return the parent which makes it easy to chain find with other actions:

page
|> find(css(".users"), & assert has?(&1, css(".user", count: 3)))
|> click(link("Next Page"))

Without the callback find returns the element. This provides a way to scope all future actions within an element.

page
|> find(css(".user-form"))
|> fill_in(text_field("Name"), with: "Chris")
|> fill_in(text_field("Email"), with: "c@keathley.io")
|> click(button("Save"))

Interacting with forms

There are a few ways to interact with form elements on a page:

fill_in(session, text_field("First Name"), with: "Chris")
clear(session, text_field("last_name"))
click(session, option("Some option"))
click(session, radio_button("My Fancy Radio Button"))
click(session, button("Some Button"))

If you need to send specific keys to an element, you can do that with send_keys:

send_keys(session, ["Example", "Text", :enter])

Assertions

Wallaby provides custom assertions to make writing tests easier:

assert_has(session, css(".signup-form"))
refute_has(session, css(".alert"))
has?(session, css(".user-edit-modal", visible: false))

assert_has and refute_has both take a parent element as their first argument. They return that parent, making it easy to chain them together with other actions.

session
|> assert_has(css(".signup-form"))
|> fill_in(text_field("Email", with: "c@keathley.io"))
|> click(button("Sign up"))
|> refute_has(css(".error"))
|> assert_has(css(".alert", text: "Welcome!"))

Windows and Screenshots

It’s possible to interact with the window and take screenshots:

resize_window(session, 100, 100)
window_size(session)
take_screenshot(session)

All screenshots are saved to a screenshots directory in the directory that the tests were run in.

If you want to customize the screenshot directory you can pass it as a config value:

# config/test.exs
config :wallaby, screenshot_dir: "/file/path"

# test_helper.exs
Application.put_env(:wallaby, :screenshot_dir, "/file/path")

Automatic screenshots

You can automatically take screenshots on an error:

# config/test.exs
config :wallaby, screenshot_on_failure: true

# test_helper.exs
Application.put_env(:wallaby, :screenshot_on_failure, true)

JavaScript

Asynchronous code

Testing asynchronous JavaScript code can expose timing issues and race conditions. We might try to interact with an element that hasn’t yet appeared on the page. Elements can become stale while we’re trying to interact with them.

Wallaby helps solve this by blocking. Instead of manually setting timeouts we can use assert_has and some declarative queries to block until the DOM is in a good state.

session
|> click(button("Some Async Button"))
|> assert_has(css(".async-result"))
|> click(button("Next Action"))

Interacting with dialogs

Wallaby provides several ways to interact with JavaScript dialogs such as window.alert, window.confirm and window.prompt. To accept/dismiss all dialogs in the current session you can use accept_dialogs and dismiss_dialogs. The default behavior is equivalent to using dismiss_dialogs.

For more fine-grained control over individual dialogs, you can use one of the following functions:

  • For window.alert use accept_alert/2
  • For window.confirm use accept_confirm/2 or dismiss_confirm/2
  • For window.prompt use accept_prompt/2-3 or dismiss_prompt/2

All of these take a function as last parameter, which must include the necessary interactions to trigger the dialog. For example:

alert_message = accept_alert session, fn(session) ->
  click(session, link("Trigger alert"))
end

To emulate user input for a prompt, accept_prompt takes an optional parameter:

prompt_message = accept_prompt session, [with: "User input"], fn(session) ->
  click(session, link("Trigger prompt"))
end

JavaScript logging and errors

Wallaby captures both JavaScript logs and errors. Any uncaught exceptions in JavaScript will be re-thrown in Elixir. This can be disabled by specifying js_errors: false in your Wallaby config.

JavaScript logs are written to :stdio by default. This can be changed to any IO device by setting the :js_logger option in your Wallaby config. For instance if you want to write all JavaScript console logs to a file you could do something like this:

{:ok, file} = File.open("browser_logs.log", [:write])
Application.put_env(:wallaby, :js_logger, file)

Logging can be disabled by setting :js_logger to nil.

Config

Adjusting timeouts

Wallaby uses hackney under the hood, so we offer a hook that allows you to control any hackney options you’d like to have sent along on every request. This can be controlled with the :hackney_options setting in config.exs.

# default values
config :wallaby,
  hackney_options: [timeout: :infinity, recv_timeout: :infinity]

# Overriding a value
config :wallaby,
  hackney_options: [timeout: 5_000]

Contributing

Wallaby is a community project. PRs and Issues are greatly welcome.

To get started and setup the project, make sure you’ve got Elixir 1.3+ installed and then:

$ mix deps.get
$ npm install -g phantomjs-prebuilt # unless you've already got PhantomJS installed
$ mix test # Make sure the tests pass!

Besides running the unit tests above, it is recommended to run the driver integration tests too:

# Run only phantomjs integration tests
$ WALLABY_DRIVER=phantom mix test

# Run all tests (unit and all drivers)
$ mix test.all