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Running Rspec examples by name, or: Running a single shared example

When an Rspec example fails, I usually investigate by running that example again using rspec <file:line>. However, this does not work with shared examples, since Rspec doesn't know in which context the shared example should be run.

But there is a different way: You can run the shared example using the -e, --example option. It takes a string value and runs all scenarios containing that substring in their full description.

This allows you to run a single uniquely named example, all examples with
similar names, all the examples in a u…

Geordi 2.7.0 released

  • Fixed #68: The "cucumber" command now fails early when @solo features fail.
  • Added: The "setup" command now prints the db adapter when prompting db credentials.
  • Fixed #71: When used without staged changes, the "commit" command will print a warning and create an empty commit. Any arguments to the command are forwarded to Git.
  • Fixed: The "commit" command will not print the extra message any more.
  • Added: The "commit" command prints a (progre…

Linux, Arial and Helvetica: Different font rendering in Firefox and Chrome

When text renders differently in Firefox and Chrome, it may be caused by a font alias that both browsers handle differently.

Situation

A machine running Linux, and a website with the Bootstrap 3 default font-family: "Helvetica Neue", Helvetica, Arial, sans-serif.

Issue

Anti-aliasing and kerning of text looks bad in Firefox. Worse, it is rendered 1px lower than in Chrome (shifted down).

Reason

Firefox resolves "Helvetica" to an installed ["TeX Gyre Heros", which is its Ghostscript clone](https://www.fontsquirrel.com/fonts/…

How to enable Chromedriver logging

When using Chrome for Selenium tests, the chromedriver binary will be used to control Chrome. To debug problems that stem from Selenium's Chrome and/or Chromedriver, you might want to enable logging for the chromedriver itself. Here is how.

Option 1: Use Selenium::WebDriver::Service

In your test setup, you may already have something like Capybara::Selenium::Driver.new(@app, browser: :chrome, options: ...), especially when passing options like device emulation.

Similar to options, simply add an extra key service and pass an ins…

Repeats

PSA: Umlauts are not always what they seem to be

When you have a string containing umlauts which don't behave as expected (are not matched with a regexp, can't be found with an SQL query, do not print correctly on LaTeX documents, etc), you may be encountering umlauts which are not actually umlaut characters.

They look, depending on the font, like their "real" umlaut counterpart:

  • ä ↔ ä
  • ö ↔ ö
  • ü ↔ ü

However, they are not the same:

>> 'ä' == 'ä'
=> false
>> 'ä'.size
=> 1
>> 'ä'.size
=> 2

Looking at how those strings are constructed reveals what is going…

Joining PDFs with Linux command line

There are several ways to merge two (or more) PDF files to a single file using the Linux command line.

If you're looking for graphical tools to edit or annotate a PDF, we have a separate card for that.

pdfjam

The pdfjoin binary from pdfjam is probably already installed on your system. Usage:

pdfjoin one.pdf two.pdf --outfile out.pdf

Pages from joined documents might be rotated. To avoid this, call it like this:

pdfjoin one.pdf two.pdf --outfile out.pdf --paper a4paper --rotateoversize false

Fo…

Repeats

Google Analytics: Change the tracked URL path

By default, Google Analytics tracks the current URL for every request. Sometimes you will want to track another URL instead, for example:

  • When an application URL contains a secret (e.g. an access token)
  • When you want to track multiple URLs under the same bucket
  • When you want to track interactions that don't have a corresponding URL + request (e.g. a Javascript button or a PDF download)

Luckily the Analytics code snippet allows you to freely choose what path is being tracked. Simple change this:

ga('send', 'pageview');

… to th…

Repeats

Matching unicode characters in a Ruby (1.9+) regexp

On Ruby 1.9+, standard ruby character classes like \w, \d will only match 7-Bit ASCII characters:

"foo" =~ /\w+/   # matches "foo"
"füü" =~ /\w+/   # matches "f", ü is not 7-Bit ASCII

There is a collection of character classes that will match unicode characters. From the documentation:

  • /[[:alnum:]]/ Alphabetic and numeric character
  • /[[:alpha:]]/ Alphabetic character
  • /[[:blank:]]/ Space or tab
  • /[[:cntrl:]]/ Control character
  • /[[:digit:]]/ Digit
  • /[[:graph:]]/ Non-blank character (excludes spaces, co…
Linked contentRepeats

Ruby blocks: Braces and do/end have different precedence

Braces and do/end are completely swappable—almost all the time. They have different precedence. It’s not often that anyone comes across what this means in practice.

TL;DR {} binds stronger than do…end (as always in Ruby, special characters bind stronger than words)

Demo

Right way

names = ['bRUce', 'STaN', 'JOlIE']

# Blocks in braces are passed to the rightmost method
print names.map { |name| name.downcase }
print(names.map do |name| name.downcase end) # equivalent
=> ["bruce", "stan", "jolie"]

Wrong way

Avoid…

Repeats

ActionMailer: Preview mails directly in your email client

In Rails, we usually have a mailer setup like this:

class MyMailer < ActionMailer::Base

  def newsletter
    mail to: 'receiver@host.tld',
      from: 'sender@host.tld',
      subject: 'My mail'
  end

end

If you want to preview your mail in the browser, you can use the Action Mailer Preview. To inspect the mail directly in your email client, just create an .eml file and open it with your client:

```ruby
mail = MyMailer.newsletter
Fil…

Repeats

Guide to localizing a Rails application

Localizing a non-trivial application can be a huge undertaking. This card will give you an overview over the many components that are affected.

When you are asked to give an estimate for the effort involved, go through the list below and check which points are covered by your requirements. Work with a developer who has done a full-app localization before and assign an hour estimate to each of these points.

Static text

  • Static strings and template text in app must be translated: Screens, mailer templates, PDF templates, helpe…
Linked contentRepeats

Things you probably didn’t know you could do with Chrome’s Developer Console

Collection of useful tools in the Chrome JavaScript console.

Make the whole page editable
This is not special to Chrome, but still a clever thing:
document.body.contentEditable=true 
Taking time
You can easily measure the time on the console with named timers:
console.time('myTime'); // Start timer
console.timeEnd('myTime'); // End timer and print the time
Reference previously inspected elements (from the Elements panel)
Variables $0, $1, … $n reference the nth-last inspected Element. $0 is the…
Linked contentRepeats

Make your Rails console (and irb) output better readable

Pour color on your Rails console with awesome_print. Turn confusing long strings into formatted output. Have objects and classes laid out clearly whenever you need it.

Put gem 'awesome_print', :group => :development into your Gemfile. Now on the Rails console you have the command ap that will give you a colored, formatted output of whatever you pass it. See the example output of the User class below.

For customization visit the repository on Github.

![awesome_print.png](https://makan…

Cucumber: How to find unused step definitions

Cucumber has an output format that prints step definitions only. You can use this to find unused ones:

  1. Temporarily add require_relative 'env' to the top of the first file in features/support. --dry-run makes Cucumber skip loading env.rb.
  2. Open a really wide terminal window.
  3. bundle exec cucumber --dry-run --format stepdefs | grep -B1 'NOT MATCHED' --no-group-separator | grep features/step_definitions

This will print all unused step definitions from your project – however, the result will include false positives. Step…

ActiveJob Inline can break the autoloading in development

We figured out, that ActiveJob Inline might lead to autoloading problems in development. The result was an exception when running an import script, which delivers async mails.

A copy of XXX has been removed from the module tree but is still active! (ArgumentError)

Our fix was to use .deliver_now and not .deliver_later (this is not a general fix, but it was okey for us). Below there are some debug hints which helped us to locate the problem:

  • We placed a pry debugger in [ActiveSupport#clear](https://github.com/rails/rails/blob…
Repeats

Building web applications: Beyond the happy path

When building a web application, one is tempted to claim it "done" too early. Make sure you check this list.

Different screen sizes and browsers

Desktops, tablets and mobile devices have all different screen resolutions. Does your design work on each of them?

  • Choose which browsers to support. Make sure the page looks OK, is usable and working in these browsers.
  • Use @media queries to build a responsive design
    • If you do not suppo…

Fixing "identify: not authorized"

Ubuntu has decided to disable PDF processing because ImageMagick and the underlying Ghostscript had several security issues.

When your Ghostscript is up to date (and receiving updates regularly), you can safely reactivate PDF processing on your computer like this:

  1. Open /etc/ImageMagick-6/policy.xml
    • For older versions of Ubuntu (or possibly ImageMagick), the path is /etc/ImageMagick/policy.xml
  2. Remove/Comment lines after <!-- disable ghostscript format types -->

If you need it enabled for a…

An incomplete guide to migrate a Rails application from paperclip to carrierwave

In this example we assume that not only the storage gem changes but also the file structure on disc.

A general approach

Part A: Create a commit which includes a script that allows you to copy the existing file to the new file structure.

Part B: Create a commit which removes all paperclip logic and replace it with the same code you used in the first commit

Part A

Here are some implementation details you might want to reuse:

  • Use the existing models to read the files from
  • Use your own carrierwave models to write t…
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