Capybara::Differ

Print the diff of snapshots with Capybara.
This will help refactoring of views.

The main feature of this library is diffing beautified htmls.

You cannot always get nice diffs with 'git diff' or 'diff' command.
But this library gives them.
This library try to remove the concerns on diff of whitespaces, linebreaks.

Expected use cases are

• Refactoring views of Rails app
  • Migration of erb -> haml/slim
  • Integration with datagrid
• Tracking sites
  • visit -> save_page -> check_page

When you run the following commands periodically,

Capybara.save_path = 'tmp/capybara'
session = Capybara::Session.new(:selenium)
session.visit 'http://rubyonrails.org/'
session.check_page('rails_page', diffy: true)

you could get the following output.

Comparing two files
--- tmp/capybara/rails_page/20180407095217.html.beauty  2018-04-11 17:04:28.000000000 +0900
+++ tmp/capybara/rails_page/20180411170428.html.beauty  2018-04-11 17:04:28.000000000 +0900
@@ -21,5 +21,5 @@
   <section>
     <p class="mobile-center">
-      <img src="/images/rails-logo.svg" width="220" height="78" alt="Ruby on Rails">
+      <img src="/images/rails-logo.svg" alt="Ruby on Rails" height="78" width="220">
     </p>
   </section>
@@ -48,15 +48,15 @@
   </section>
   <section class="version">
-    <p><a href="http://weblog.rubyonrails.org/2018/3/29/Rails-5-0-7-and-5-1-6-have-been-released/">
-        Latest version — Rails 5.1.6
+    <p><a href="http://weblog.rubyonrails.org/2018/4/9/Rails-5-2-0-final/">
+        Latest version — Rails 5.2.0
         <span class="hide-mobile">
-          released March 29, 2018
+          released April 9, 2018
         </span></a></p>
     <p class="show-mobile"><small>
-        Released March 29, 2018
+        Released April 9, 2018
       </small></p>
   </section>
   <section class="video-container">
-    <iframe src="https://www.youtube.com/embed/OaDhY_y8WTo" frameborder="0" allowfullscreen="" class="video"></iframe>
+    <iframe src="https://www.youtube.com/embed/OaDhY_y8WTo" allowfullscreen="" class="video" frameborder="0"></iframe>
   </section>
   <section class="interior">

This library can display diff using git diff (default)
Check the output without diffy option

session.visit 'http://rubyonrails.org/'
session.check_page('rails_page')

Supports the option(context) to change the number of lines of context. It sets the value of --unified=(default 3) of git diff option.

session.check_page('test_page', context: 0)

It's possible to change the value from command line using env var if you have code something like the following.

session.check_page('test_page', context: ENV.fetch('CONTEXT', 3))

• git
• https://github.com/samg/diffy
• https://github.com/threedaymonk/htmlbeautifier

Add this line to your application's Gemfile:

gem 'capybara-differ'

And then execute:

$ bundle

Or install it yourself as:

$ gem install capybara-differ

In your system test(feature spec)

page.check_page('name_of_snapshot', selector: 'table')

You can get the diff from the history of Capybara:Session#save_page.

In this example(when you add class to table header),
you will see the diff of latest snapshot and the first snapshot in tmp/capybara/name_of_snapshot/ .

       <th class="id">
         ID
       </th>
-      <th class="name">
+      <th class="name foo">
         Name
       </th>

You can reset the target snapshot by removing files in tmp/capybara/name_of_snapshot/ .
Or remove the directory of snapshots.

By default, the target snapshot is the first version.

You can compare with the previous version with the following option

page.check_page('name_of_snapshot', compare_with: :previous, selector: 'table')

This library depends on diffy You can pass the options for diffy something like 'context'.

page.check_page('name_of_snapshot', selector: 'table', diffy: {context: 3})

And you can change the format of output with diffy with 'format' option. (default :color)

page.check_page('name_of_snapshot', selector: 'table', diffy: {format: :html_simple})

• Add an option to suppress log
• Others

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/kyamaguchi/capybara-differ.

The gem is available as open source under the terms of the MIT License.