[rspec-users] [ANN] assert2-0.4.6 provides assert_xhtml, an alternative to assert_select

Phlip phlip2005 at gmail.com
Thu Mar 26 08:53:35 EDT 2009


Consider the following monstrosity, coded using assert_select:

   assert_select "div#logo_box img[src=/0000/0001/logo.gif][alt=My Company]"

Now, behold it rewritten to use assert_xhtml:

   assert_xhtml do
     div.logo_box! do
       img :src => /logo.gif$/, :alt => 'My Company'

That sample contains more Ruby; it's not just one big string.

Still not convinced? Oh, I forgot the <a> around the <img>! Try this:

   assert_xhtml do
     div.logo_box! do
       a :href => '/' do
         img :src => /logo.gif$/, :alt => 'My Company'

And we had an issue with the small logo sneaking into the logo_box once. Let's 
exclude it:

   assert_xhtml do
     div.logo_box do
       a :href => '/' do
         img :src => /logo.gif$/, :alt => 'My Company'
       without!{ img :src => /mini_logo.gif/ }

Imagine adding all that to assert_select - it would get much harder to read, and 
more complex. assert_xhtml uses Nokogiri::HTML::Builder notation, so anything it 
can build, you can query.

Version 0.4.6 adds all the following features. To begin, enter:

   gem install nokogiri assert2

== require 'assert2/xhtml' ==

All assert{ 2.0 } dependencies are optional. If you have Nokogiri
(>=1.2.2), you can test Rails views like this:

      user = users(:Moses)
      get :edit_user, :id =>  user.id

      assert_xhtml do

        form :action =>  '/users' do
          fieldset do
            legend 'Personal Information'
            label 'First name'
            input :type =>  'text',
                  :name =>  'user[first_name]'
                  :value =>  user.first_name


That's a Rails functional test on a form. The assertion expects the form
to target the given action, and contain a fieldset, a legend, a label, and
a populated text input field. The assertion forgives any other details,
such as intervening structural tags, excess spaces, or extra attributes;
and complains if any required detail is missing, out of order, or ill-formed.

The DSL inside that block is Nokogiri::HTML::Builder notation. Generally
speaking, anything Nokogiri can build, you can specify.

=== arguments ===

Call assert_xhtml(my_xml){} to interrogate your XML. When called without
an argument, the method reads @response.body.

=== without! ===

Every assert* has a matching deny* method. assert_xhtml recognizes the
special element without! as a request to fail if the given elements
do indeed appear in your output:

     get :info, :record_id => record.id
     assert_xhtml do
       div :class => :content do
         without!{ div :class => :download }

That assertion will fail if the outer <div class='content'> tag does not
exist, or if any inner <div class='download'> does exist.

The without! element respects your document layout. This assertion

     assert_xhtml SAMPLE_LIST do
       ul{ li{ ul{ li 'Sales report'
           without!{ li 'All Sales report criteria' } } } }

...even though the target document contains an <li>All Sales report

     <ul style='font-size: 18'>
           <li>Billings report</li>
           <li>Sales report</li>
           <li>Billings criteria</li>
           <li>Common system</li>
           <li>All Sales report criteria</li>
           <li>All Billings reports</li>

The two <li> elements appear in different <ul> lists, so the assertion
does not associate them.

The committee does not yet know what without!{ without!{} } does, so please
do not rely on its current behavior, whatever that is!

=== escapes ===

Certain elements, such as <select> and <id>, have the same names as internal
methods. If you experience a bizarre error message, such as "wrong argument
type Hash (expected Array)", add a ! to the end of the element, like this:

     assert_xhtml do
       h2 'Sites'

       select! :id => 'sites',
               :name => 'sites[]',
               :multiple => :multiple,
               :size => SaleController::LIST_SIZE

=== text ===

An element such as h3{ 'text' } will match <h3> text </h3>, with leading or
trailing blanks, but it won't match <h3><span>text</span></h3>. This rule
prevents runaway matches between high- and low-level elements.

The example for the next section illustrates how to mix text and attribute
specifications on the same element.

A text specification may be a /regexp/.

=== :xpath!=> ===

assert_xhtml works by throwing away structural information. If you need
more control over your structure, use an :xpath! attribute to apply raw
XPath specifications to your target elements.

This assertion detect the rather pedestrian fact that your <title>
element remains inside your <html><head> block - and it did not
escape and rampage off to somewhere else:

     assert_xhtml do
       title :xpath! => 'parent::head/parent::html' do
         text 'Chamber of Commerce - Info - Hope Orphanage'

Note the XPath evaluates as a predicate of the target <title>, so its parent 
axis lists the familiar elements in reverse.

That code also shows the 'text' directive, inserting text contents directly
into the enclosing element. A future version of Nokogiri will allow the
element's first argument to specify its text.

An :xpath! of a number evaluates to the 1-based index of an item in its
parent. This assertion forces list items to appear in the correct order:

     assert_xhtml do
       ul :style => 'font-size: 18' do
         li 'model' do
           li(:xpath! => 1){ text 'Sales report'  }
           li(:xpath! => 2){ text 'Billings report' }
           li(:xpath! => 3){ text 'Billings criteria' }

=== :verbose! => true ===

Sometimes when an assertion fails, you can't tell why. To see each
context the assertion considers, add :verbose! => true to the lowest
element you know works, and run the tests:

     assert_xhtml SAMPLE_FORM do
       fieldset do
         li :verbose! => true do
           label 'First name', :for => :user_first_name

The verbose option works as "spew", not as a diagnostic, and it reports
each considered element's contents.

Because XPath evaluates the <label>, in our example, before the <li>, you
might need to comment the <label> out to see a successful spew on the <li>.

=== scope ===

assert_xhtml{} yields its block to Nokogiri::HTML::Builder, which turns
every method call into an HTML element. This freedom comes at a price -
you can't easily call your own methods!

Use this scope trick to pass your outer scope into the specification:

      get :edit_user, :id => users(:Moses).id
      scope = self

      assert_xhtml do
        form :action => '/users' do
          input :value => scope.users(:Moses).first_name

Notice we could improve that test by declaring a variable,
user = users(:Moses), in the outer scope, and simply passing
the user variable itself into the specification.

=== :class=> ===

The :class attribute is magic. This assertion passes...

     assert_xhtml SAMPLE_LIST do
       ul :class => :kalika do
         li 'Billings report'

...despite the actual HTML contains <ul class='kalika goddess'>. This feature
simulates the CSS Selector notation that matches classes by their cascading

=== class & ID shortcuts ===

Nokogiri expands div.rad.thing! to <div class='rad' id='thing'/>. That
means you don't need to write div :class => 'rad', :id => 'thing' (or
ul :class => :kalika). You can then put other arguments after the shortcut,
and the <div> in our example receives them, too.

=== diagnostic message ===

When this assertion fails, it attempts to print out...

  - your reference elements, rendered as HTML
  - each "near-miss" region of your sample HTML

The next version will feature much better diagnostics. Until they work, if these 
diagnostics are not sufficient, put :verbose! on the lowest element you think 
works, and comment out its contents...

=== RSpec ===

The matching "specification", in RSpec language, is be_html_with{}.
Its syntax and behavior are the same:

   it 'should have a cute form' do
     render '/users/new'

     response.body.should be_html_with{
       form :action => '/users' do
         fieldset do
           legend 'Personal Information'
           label 'First nome'
           input :type => 'text', :name => 'user[first_name]'

Good hunting!


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