HOWTOs for Ruby on Rails and JavaScript

About the HTML and the BODY tag

The <html> and <body> tags both come with some non-default behavior that you know from other tags.
Do not try to style html or body for positioning, width/heigth, or similar. Every browser has its own caveats and you can not test them all.

Generally speaking:

Use the html tag to define your page's default background color (because on short pages or large screens, your body may not be as tall as the browser window).
Use the html tag to define a base font-size so you can use [rem units](https://www.sitepoint.com/underst...

phrogz.net

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Pierce through Javascript closures and access private symbols

If you are writing any amount of Javascript, you are probably using closures to hide local state, e.g. to have private methods.

In tests you may find it necessary to inspect a variable that is hidden behind a closure, or to mock a private method using Jasmine spies.

You can use the attached Knife helper to punch a hole into your closure, through which you can read, write or mock local symbols:

klass = (->

 privateVariable = 0

 privateMethod = ->
   ...

knife.js.coffee

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RubyMine crashes Ubuntu 11.04 window decorator on exit

My RubyMine (and it seems like many other Java GUI applications) crashes the Compiz window decorator almost every time on exit. This also seems to happen for the Unity decorator.

Update: The commited fix from below seems to have made it into the stable Ubuntu repository.

Easy mode

You can restore window decorations by executing this command:

gtk-window-decorator --replace &

This is only a temporary fix.

Hard mode

Also, there is a committed fix that is n...

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Strip carriage returns in submitted textareas

When submitting textareas, browsers sometimes include carriage returns (\r) instead of just line feeds (\n) at the end of each line. I don't know when this happens, and most of the time it doesn't matter.

In cases where it does matter, use the attached trait to remove carriage returns from one or more attributes like this:

class Note
  does 'strip_carriage_returns', :prose, :code
end

Here is the test that goes with it:

describe Note do

  describe 'before_validation' do...

strip_carriage_returns_trait.rb

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Accessing Rails config in webpack(er)

It is possible to access Rails config (for example secrets) from within your webpack bundles, thanks to rails-erb-loader. When using webpacker, the setup is like this:

Install rails-erb-loader:
```
yarn add rails-erb-loader
```

Add this to your config/webpacker/environment.js:

environment.loaders.prepend('erb', {
  test: /\.erb$/,
  enforce: 'pre',
  use: [{
    loader: 'rails-erb-loader',
  }]
})

Start using erb. For examp...

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The Easiest Way to Parse URLs with JavaScript

A very clever hack to parse a structured URL object is to create a <a> element and set its href to the URL you want to parse.

You can then query the <a> element for its components like schema, hostname, port, pathname, query, hash:

var parser = document.createElement('a');
parser.href = 'http://heise.de/bar';
parser.hostname; // => 'heise.de'
pathname = parser.pathname; // => '/bar'

if (pathname[0] != '/')
  pathname = '/' + pathname // Fix IE11

One advantag...

tutorialzine.com

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Rails: Default generators

This is a visualization of the files that will be generated by some useful rails generators. Invoke a generator from command line via rails generate GENERATOR [args] [options]. List all generators (including rails generators) with rails g -h.

generator	model	migration	controller	entry in `routes.rb`	views	tests
scaffold	✔	✔	✔	✔	✔	✔
resource	✔	✔	✔ ...

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How to open a new tab with Selenium

Until recently, you could open a new tab via window.open when using execute_script in Selenium tests. It no longer works in Chrome (will show a "popup blocked" notification).

This is because browsers usually block window.open unless the user interacted with an element for security reasons. I am not sure why it did work via Selenium before.

Here is an approach that will insert a link into the page, and have Selenium click it:

path = "/your/path/here"
id = "helper_#{SecureRandom.hex(8)}"
execute_script <<-JAVASCRIPT
  ...

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Fix "subprocess installed post-removal script returned error exit status ..." when installing/removing/updating a package with apt

If you get an error like:

subprocess installed post-removal script returned error exit status 78

when installing/removing/updating a package with apt you should check the postinst, postrm, prerm, ... script in /var/lib/dpkg/info/.

For example in my case I had a problem when removing varnish:

Removing varnish (4.0.3-2~trusty) ...
dpkg: error processing package varnish (--remove):
 subprocess installed post-removal script returned error exit status 78
Errors were encountered while processing:
 varnish

So I checked ...

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Selenium: How to close another tab (popup)

If you open a pop-up window [1] in your Selenium tests and you want to close it, you can do this:

# Find our target window
handle = page.driver.find_window("My window title")

# Close it
page.driver.browser.switch_to.window(handle)
page.driver.browser.close

# Have the Selenium driver point to another window
last_handle = page.driver.browser.window_handles.last
page.driver.browser.switch_to.window(last_handle)

Mind these:

find_window returns a window handle, which is something like `"{485fa8bd-fa99-...

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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:

Temporarily add require_relative 'env' to the top of the first file in features/support. --dry-run makes Cucumber skip loading env.rb.
Open a really wide terminal window.
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...

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Hack of the day: One-liner to run all changed Cucumber features

Similar to our snippet that runs all Cucumber features matching a given string, the following will run all modified or new Cucumber features by looking at your git status:

git status --short | grep -v '^ D ' | grep '.feature' | sed 's/.. //' | tr '\n' ' ' | xargs geordi cucumber

If you want to know what each of the above commands does, see [explainshell](http://explainshell.com/explain?cmd=git+status+--short+%7C+grep+-v+%27%5E+D+%27+%7C+grep+%27.feature%27+%7C+sed+%27s%2F..+%2F%2F%27+%7C+tr+%27%5Cn%27+%27+%27+%7C...

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Take care of existing users when upgrading Clearance

When upgrading Clearance, pay attention whether the password hashing strategy might have changed. Old clearance versions (< 1.0) used SHA1-encrypted passwords by default. Current versions default to BCrypt.

If you simply upgrade without taking this into account, users will get a BCrypt::Errors::InvalidHash when trying to sign in. Your tests will not notice this, since they create new users for each scenario.

To fix it, you'll either have to force all users to reset their passwords, or you can allow old users to keep signing in with t...

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Quick HTML testing with RubyMine

If you need to test some HTML, e.g. an embed code, you can use RubyMine's "scratch files":

File > New Scratch File (or Ctrl + Shift + Alt + Ins)
Select "HTML" as file type
Write or paste the HTML
Move your mouse to the upper right corner of the scratch file editor. Pick a browser to instantly open your file.

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randym/axlsx · GitHub

Axlsx is an incredible gem to generate "Office Open XML" spreadsheet files (XLSX). Does not break on large spreadsheets and supports a ton of features like graphs.

API looks mature and existing code is easy to migrate when coming from the spreadsheet gem.
The documentation of some methods is a bit out of date, but you'll find your way around the gem's code.

No support for reading files, however. :( If you want to open XLSX spreadsheets (for example to confirm your output in tests), you can use [roo](h...

github.com

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Prevent your Firefox from auto-updating

Note that if you plan to freeze your Firefox versions because your Selenium tests break whenever Firefox updates, there is a better way that lets you keep an up-to-date Firefox. Mozilla has stated that they will no longer provide security patches for any but the most recent versions of Firefox. So running an old Firefox should not be a long-term solution for anything.

If you still wish to disable the auto-update in Firefox, a poste...

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Puppet: Could not evaluate: Field 'device' is required

If you get an error like this for a puppet mount:

$ > puppet agent --test 
Info: Retrieving pluginfacts
Info: Retrieving plugin
Info: Loading facts
Info: Caching catalog for example.makandra.de
Info: Applying configuration version '1483001792'
Info: Computing checksum on file /etc/fstab
Info: FileBucket got a duplicate file {md5}34b9adc036cf1dbd2392df84f921547d
Notice: /Stage[main]/Foobar/Swap_file::Files[default]/Mount[/var/swapfile]/ensure: defined 'ensure' as 'defined'
Error: /Stage[main]/Foobar/Swap_file::Files[default]/Mount[/var/s...

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How to remove RSpec "old syntax" deprecation warnings

RSpec 3.0 deprecates the :should way of writing specs for expecting things to happen.

However, if you have tests you cannot change (e.g. because they are inside a gem, spanning multiple versions of Rails and RSpec), you can explicitly allow the deprecated syntax.

Fix

Inside spec/spec_helpber.rb, set rspec-expectations’ and/or rspec-mocks’ syntax as following:

RSpec.configure do |config|
  # ...
  config.mock_with :rspec do |c|
    c.syntax = [:should, :expect]
 ...

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How to upgrade Cucumber on Rails 3+

Run bundle update cucumber capybara cucumber-rails to update to the newest versions.
Backup your features/support/path.rb to be able to add your own paths again after the cucumber installation script in step 4.

Backup your features/support/env.rb file to be able to reintegrate parts like your blueprints setup:

ENV["RAILS_ENV"] ||= "cucumber"
require File.expand_path(File.dirname(__FILE__) + '/../../config/environment')
require 'spec/support/blueprints'

Run `$ rails generate cucumber:install --capyba...

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Removing MiniTest warnings from Rails 4 projects

Warnings like those below may originate from rspec or shoulda-matchers or other gems that have not updated yet to the new MiniTest API.

One

Warning: you should require 'minitest/autorun' instead.
Warning: or add 'gem "minitest"' before 'require "minitest/autorun"'
# (backtrace)

Solution: Add gem 'minitest' to your Gemfile, before any rspec gem.

Another

MiniTest::Unit::TestCase is now Minitest::Test. From /Users/makandra/.rvm/rubies/ruby-1.9.3-p484/lib/ruby/1.9.1/tes...

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MySQL: How to dump single tables instead of a complete database

Sometimes you want to test migrations with production or staging data. Dumping single tables makes sense if a complete dump would be to big.

mysqldump -u deploy_user -p application_production table1 table2 table2 > table1_table2_table2.sql.dump

Hint: If a table has to many constraints, a complete dump could be more handy.

Perform HTTP basic authentication in Cucumber (with or without Selenium)

This card describes a Cucumber step that lets you say:

When I perform basic authentication as "username/password" and I visit the admin area

The path component ("... the admin area") is parsed through your path_to helper in features/support/paths.rb.

Capybara

The step definition is part of Spreewald. The step has been tested with multiple versions of Capybara, Rack::Test and Selenium.

Webrat (legacy)

This is a simpler version of the step above:

When /...

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How to pair a Bose Quiet Comfort 35 with your Ubuntu computer

You need to disable "Bluetooth low energy", then follow these core steps:

Make sure the headphones are in pairing mode.
Pair with System Settings > Bluetooth. On 16.04 I had to choose "proceed without pairing" and enter the PIN "0000"
Select & test the headphones in System Settings > Sound. Choose High Fidelity Playback (A2DP Sink).

I also had to install a package with sudo apt-get install pulseaudio-module-bluetooth and load it with pactl load-module module-bluetooth-discover. Put the latter command into ~/.bashrc or you'll...

askubuntu.com

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Linux: How to add a task bar to VNC displays

If you are using VNC to run Selenium tests, it may be hard to see what's going on since by default there is no list of open windows and Alt+Tab won't work.

Solving that is easy:

Install a panel of your choice (like lxpanel) which offers task switching:
```
sudo apt-get install lxpanel
```
(You can't use gnome-panel because it won't start twice -- but lxpanel does a good job)
To have that panel appear on VNC screens by default, edit ~/.vnc/xstartup...

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