3904 cards

Raising JavaScript errors in Cucumber scenarios and how to silence them for particular scenarios

Raising JavaScript errors in Cucumber

With selenium JavaScript errors do not cause any failure in your cucumber scenarios. To archive a failure we can use the the Ruby bindings to Selenium Webdriver expose the Webdriver logging API introduced in version 2.38 .

The following step can be used:

Then /^there should be no JavaScript errors$/ do
  if alert_present?
    # Chrome 54 and/or Chromedriver 2.24 introduced a breaking change on how
    # accessing browser logs work.
    # Apparently, while an alert/confirm is open, Chrome...

How to list updateable dependencies with Bundler and Yarn


bundle outdated [--filter-major|--filter-minor|--filter-patch]

Example output for bundle outdated --filter-major



yarn outdated

Example output



Insomnia helps you querying your API

Insomnia is a GUI tool to help you communicating with an API. There are also other tools to do this, e.g. Postman or or the command line tool cURL.

While it is quite similar to Postman, I found the UI to be less cluttered and therefore easier to use.


The usage is almost self explanatory.

You can install i...


Whenever: Don't forget leading zeros for hours!

Whenever is a Ruby gem that provides a nicer syntax for writing and deploying cron jobs.

Leading zeros are important for whenever if you use the 24-hours format!

This schedule.rb:

every 1.day, at: '3:00', roles: [:primary_cron] do
  runner 'Scheduler.delay.do_things'

will lead to this crontab entry (crontab -l):

0 15 * * * /bin/bash -l -c 'cd /var/www/my-project/releases/20180607182518 && bin/rails runner -e production '\''Scheduler.delay.do_things'\'''

Which would run on 3pm instead of 3am.

Using the l...


Git: How to rebase your feature branch from one branch to another

In a nutshell: Use git rebase source-commit --onto target-branch

  • target-branch means "branch you want to be based on"
  • source-commit means "commit before your first feature commit"

Let's say my-feature-branch is based on master and we want it to be based on production. Consider this history (topmost = latest):

  • commit 6 [my-feature-branch]
  • commit 5
  • commit 4 [master]
  • commit 3
  • commit 2 [production]
  • commit 1

Here, master has commits that are not yet in production (number 3 and 4).



Git stash: Working with old Entries

First find the reference for the entry you want through looking at the stash:

$ git stash list
stash@{0}: WIP on feature/foo
stash@{1}: WIP on feature/bar
stash@{2}: WIP on fix/baz

Now you can simply use that reference, but curly braces must be escaped:

git stash pop stash@\{1\}

or quoted:

git stash apply "stash@{1}"

Quick reminder to [not shoot yourself in the foot](https://makandracards.com/makandra/634-use-the-git-stash-withou...

Linked content

Some tips for upgrading Bootstrap from 3 to 4

Recently I made an upgrade from Bootstrap 3 to Bootstrap 4 in a bigger project. Here are some tips how to plan and perform such an upgrade. The effort will scale with the size of the project and its structure. If your stylesheets already follow strict rules, it may take less time to adapt them to the new version.


There are several gems and libraries that works well with bootstrap or provide at least stylesheets/plugins to easily integrate the bootstrap theme. But very often they only work with specific version or are no long...

ActiveType #change_association: Define { autosave: true } on parent models

Consider the following models and form models:

class Parent < ApplicationRecord
  has_many :children, class_name: 'Child', foreign_key: 'parent_id'

class Parent::AsForm < ActiveType::Record[Parent]
  change_association :children, class_name: 'Child::AsForm', foreign_key: 'parent_id', autosave: true, inverse_of: :parent

  accepts_nested_attributes_for :children
  validates_associated :children
class Child < ApplicationRecord
  belongs_to :parent, inverse_of: :children

class Child::AsForm < ActiveType::Reco...

How to fix: Version in "./docker-compose.yml" is unsupported

When running an older version of docker-compose you might see the following error:

ERROR: Version in "./docker-compose.yml" is unsupported. You might be seeing this error because you're using the wrong Compose file version. Either specify a supported version (e.g "2.2" or "3.3") and place your service definitions under the `services` key, or omit the `version` key and place your service definitions at the root of the file to use version 1.
For more on the Compose file format versions, see https://docs.docker.com/compose/compose-file/

Linux: How to make a terminal window title reflect the current path

By default, your terminal emulator (Gnome Terminal, Terminator, etc.) sets some kind of window title to reflect the shell type you are running (e.g. /bin/bash).
This is most often not too helpful, but you can change that from your shell.

To set a specific title, print an escape sequence like this:

echo -en "\033]0;Hello\a"

You can easily include the current path:

echo -en "\033]0;$(pwd)\a"

Or, to replace your home directory's part with a tilde:

echo -en "\033]0;$(pwd | sed -e "s;^$HOME;~;")\a"



Shortcut for getting ids for an ActiveRecord scope

You can use .ids on an ActiveRecord 4+ scope to pluck all the ids of the relation

User.where("users.name LIKE 'Foo Bar'").ids

# same as (since Rails 3.2)
User.where("users.name LIKE 'Foo Bar'").pluck(:id)

If you are stuck on Rails 2.3 you can use Edge Rider's collect_ids:

User.where("users.name LIKE 'Foo Bar'").collect_ids(:id)

Carrierwave processing facts

  1. Class-level process definitions are only applied to the original file
  2. Versions are generated based on the processed original file
  3. Callbacks (before/after) are applied to original file and each version by itself
  4. Under the hood, a version is an instance of the uploader class that has no versions
  5. Version uploader and original uploader can be distinguished by checking #version_name: version uploaders return the version name, whereas the original uploader instance returns nil
  6. Version instances do not have a re...

Difference between respond_to/format and params[:format]

To return non-HTML responses (like XLS spreadsheets), we usually use the

respond_to do |format|
  format.xls do
    # send spreadsheet

This is often, but not always the same as checking for params[:format] == :xls, so don't rely on this when e.g. one format checks for authorization and the other doesn't.

params[:format] is only set when a user explicitly puts a .xls at the end of the URL.

The format.xls block also responds when the user's browser requests the application/excel MIME type.

If Intern...

WYSIWYG with Action Text

Rails 6 includes a WYSIWYG editor, Action Text. It works out of the box quite well, but chances are that you want to add some custom functionality. This card contains some tips how to achieve this.


Basically, follow the guide in the Rails documentation. The automated script may not work with the way webpacker is configured in your project, but it should be easy to fix.

If you don't want the default c...

Linked content

Rails: Postgres Partial Indexing

PostgreSQL has partial indexes. With a partial index you tell Postgres to only index rows matching a given query.

Some uses cases for a partial index:

  • You want a uniqueness index, but only under some conditions
  • Your table is very large and indexing every row becomes expensive

The linked article shows how to create a partial index with Rails.


DNS debug tools

There are several tools for DNS debugging which offer you more or less information. Most of the time the more simple ones, like host oder nslookup will be sufficient.


simple DNS lookup utility.

>host heise.de
heise.de has address
heise.de has IPv6 address 2a02:2e0:3fe:1001:302::
heise.de mail is handled by 10 relay.heise.de.


query Internet domain name servers. Nslookup has two modes: interactive and non-interactive.

>nslookup heise.de

How to fix "Command "webpack" not found"

I just ran into this deployment error after switching from the asset pipeline to webpack:

01:05 deploy:assets:precompile
      01 bundle exec rake assets:precompile
      01 Compiling...
      01 Compilation failed:
      01 yarn run v1.22.5
      01 error Command "webpack" not found.
rake stderr: Nothing written

The problem is not related to the "webpack" dependency. You probably just forgot to add a binstub to run "yarn install":

Add these lines to "bin/ya...

Linked content

InfoQ: How to Design a Good API & Why it Matters

A well-written API can be a great asset to the organization that wrote it and to all that use it. Given the importance of good API design, surprisingly little has been written on the subject. In this talk (recorded at Javapolis), Java library designer Joshua Bloch teaches how to design good APIs, with many examples of what good and bad APIs look like.

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