Mâché
Mâché (pronounced "mash-ay") is a tool that helps you to write cleaner and more expressive acceptance tests for your Ruby web applications using page objects.
Table of Contents
What is a Page Object?
A page object is a data structure that provides an interface to your web application for the purposes of test automation. For example, it could represent a single HTML page, or perhaps even a fragment of HTML on a page.
From Martin Fowler:
A page object wraps an HTML page, or fragment, with an application-specific API, allowing you to manipulate page elements without digging around in the HTML.
Capybara can get us part of the way
there. It allows us to work with an API rather than manipulating the HTML
directly, but what it provides isn't an application specific API. It gives us
low-level API methods like find, fill_in, and click_button, but it
doesn't provide us with high-level methods to do things like "sign in to the
app" or "click the Dashboard item in the navigation bar".
This is where page objects come in. Using Mâché, we can define a page object
class called SignInPage and use it any time we want to automate
authenticating with our app. It could handle visiting the sign in page,
entering the user's credentials, and clicking the "Sign in" button.
Getting Started
Let's dive straight in and take a look at an example. Consider the following HTML fragment for the welcome page in our app:
<html>
<body>
<header>
<h1>Welcome</h1>
<div id="flash" class="notice">lorem ipsum</div>
</header>
<nav>
<ul>
<li><a href="/foo" class="selected">foo</a></li>
<li><a href="/bar">bar</a></li>
<li><a href="/baz">baz</a></li>
</ul>
</nav>
<main>
lorem ipsum
</main>
</body>
</html>To define a WelcomePage page object class to wrap this HTML page, we extend
the Mache::Page class. The only method our class needs to provide is path,
this tells Mâché where to go when we want to visit the page:
require "mache"
class WelcomePage < Mache::Page
def path
"/welcome"
end
endWe can visit our welcome page using our page object:
page = WelcomePage.visit
page.current? # trueMâché also handily exposes the Capybara API on our page object:
page.find("main").text # "lorem ipsum"Elements
To make our page object more useful, we can define an element on our page
object class using the element macro. An element is simply an HTML element
that we expect to find on the page using a CSS selector.
Let's define a main element to represent the main section of our HTML page:
require "mache"
class WelcomePage < Mache::Page
element :main, "main"
def path
"/welcome"
end
endWe can query the main element as an attribute of our page object:
page.main.text # "lorem ipsum"Components
For elements that can be shared across any number of page object classes it may
be useful to define a reusable component by extending the Mache::Node class.
A component can contain any number of elements (or even other components).
Let's define a Header component to represent the header of our HTML page:
require "mache"
class Header < Mache::Node
element :title, "h1"
endWe can mount the Header component in our page object class at a given CSS
selector using the component macro:
require "mache"
class WelcomePage < Mache::Page
component :header, Header, "header"
element :main, "main"
def path
"/welcome"
end
endQuerying a component of our page object is much the same as with an element:
page.header.title.text # "Welcome"Helpers
Mâché provides helpers for testing Rails apps.
Flash
The Flash helper provides methods for testing flash messages. First define a
flash in your page object class:
require "mache"
require "mache/helpers/rails"
class WelcomePage < Mache::Page
include Mache::Helpers::Rails::Flash
flash "#flash"
endThen you can query the flash on your page object:
page.has_message?(:success, "lorem ipsum")
page.has_message?(:success, /lorem ipsum/)There are even convenience matchers for the common types of flash messages:
page.has_success_message?("lorem ipsum")
page.has_notice_message?("lorem ipsum")
page.has_alert_message?("lorem ipsum")
page.has_error_message?("lorem ipsum")Routes
The Routes helper mixes the Rails URL helpers into your page object class.
This allows you to use the *_path and *_url methods as you normally would
in your Rails.
require "mache"
require "mache/helpers/rails"
class WelcomePage < Mache::Page
include Mache::Helpers::Rails::Routes
def path
welcome_path
end
endExamples
Let's look at an example of an acceptance test for our WelcomePage. Note that
the Header, NavItem, and Nav components can be reused in any other page
object classes we may define later for our web application.
require "mache"
require "mache/helpers/rails"
class Header < Mache::Node
element :title, "h1"
end
class NavItem < Mache::Node
def selected?
node[:class].include?("selected")
end
end
class Nav < Mache::Node
components :items, NavItem, "a"
def selected_item
items.find(&:selected?)
end
end
class WelcomePage < Mache::Page
include Mache::Helpers::Rails::Flash
include Mache::Helpers::Rails::Routes
component :header, Header, "header"
component :nav, Nav, "nav"
element :main, "main"
flash "#flash"
def path
welcome_path
end
end
feature "Welcome page" do
let(:home_page) { WelcomePage.visit }
scenario "A user visits the welcome page" do
expect(home_page).to be_current
# header
expect(home_page).to have_header
expect(home_page.header.title).to eq("Welcome")
# nav
expect(home_page).to have_nav
expect(home_page.nav).to have_items
expect(home_page.nav.items.count).to be(3)
expect(home_page.nav.items[0].text).to eq("foo")
expect(home_page.nav.items[1].text).to eq("bar")
expect(home_page.nav.items[2].text).to eq("baz")
expect(home_page.nav.selected_item).to eq("foo")
# main
expect(home_page.main.text).to eq("lorem ipsum")
# flash
expect(home_page).to have_flash
expect(home_page).to have_notice_message("lorem ipsum")
end
endDocumentation
Read the API reference on RubyDoc.
License
Mâché is licensed under the MIT License.