Whenever you have to deal with randomness in a jasmine test there are some spy strategies to help you out!

Let's say we have a method Random.shuffle(array) to shuffle an array randomly and a class that uses shuffle within the constructor.

returnValue & returnValues

it('shuffles the array', () => {
  spyOn(Random, 'shuffle').and.returnValue([3, 2, 1])
  array = [1, 2, 3]
  
  testedClass = new testedClass(array)
  
  expect(Random.shuffle).toHaveBeenCalled()
  expect(testedClass.array).toEqual([3, 2, 1])
})

If you have...

You might know a few examples, where you configure some library via a block. One example is the Rails configuration:

Rails.application.configure do |config|
  config.enable_reloading = false
end

This card describes a simple example on how to make your ruby library configurable.

Example

module FooClient
  class Client
    class_attribute :config

    def self.configure
      self.config ||= Configuration.new
      yield(config)
    end

    def test
      uri = URI.parse(FooClient::Client.config.endpoint)
      Net:...

Starting with Ruby 1.9, most #each methods can be called without a block, and will return an enumerator. This is what allows you to do things like

['foo', 'bar', 'baz'].each.with_index.collect { |name, index| name * index }
# -> ["", "bar", "bazbaz"]

If you write your own each method, it is useful to follow the same practice, i.e. write a method that

• calls a given block for all entries
• returns an enumerator, if no block is given

How to write a canonical each method

To write a m...

The goal is to get Jasmine specs running in a Rails project using Webpacker, with the browser based test runner. Should be easily adaptable to a pure Webpack setup.

Step 1: Install Jasmine

yarn add jasmine-core

Step 2: Add two separate packs

Since we do not want to mix Jasmine into our regular Javascript, we will create two additional packs. The first only contains Jasmine and the test runner. The second will contain our normal application code and the specs themselves.

We cannot...

When an AJAX request raises an exception on the server, Rails will show a minimal error page with only basic information. Because all Unpoly updates work using AJAX requests, you won't get the more detailled better_errors page with the interactive REPL.

Below is an event listener that automatically repeats the request as a full-page load if your development error shows an error page. This means you get...

You can use the config.x configuration in combination with config_for to configure global settings for your Rails 4.2+ application.

Example

In your config/application.rb assign the settings from e.g. config/settings.yml as follows:

module FooApplication
  class Application < Rails::Application
    config.x.settings = config_for(:settings)
  end
end

The config/settings.yml might look as follows:

shared: &shared
  email: info@example.com
...

When you generate a URL in a mailer view, ActionMailer will raise an error unless you previously configured it which hostname to use.

There are two options to set the default_url_options of ActionMailer:

1. Hardcoded solution (preferred solution when using Rails with ActiveJob/Sidekiq or Cronjobs)
2. Dynamic solution

1. Hardcoded solution

When you are sending mails from outside the request cycle, e.g. ActiveJob/Sidekiq or Cronjobs, y...

Besides Plotting graphs in Ruby with Gruff, which comes handy for many uses cases, you sometimes might need configuration for more advanced plots, e.g. for academic concerns. Then using Gnuplot, the first academic open source plotting software, might be a good option.

There are several wrappers for Ruby available and I mainly looked at one of the two most frequently used ones, which are [ruby_gnuplot](https://github.com/rdp/ruby_gnuplot...

tl;dr When browsers start to adapt proposals from Open UI, it might not be necessary to use any 3rd party libraries to have nice components and controls in web applications e.g. selects. It would require only a minimum of CSS and Javascript to get them working and looking good.

The purpose of the Open UI, a W3C Community Group, is to allow web developers to style and extend built-in web UI components and controls, such as <select> dropdowns, checkboxes, radio buttons, and date/color pickers.

To do that, we’ll need to fully speci...

tl;dr

Set profile.password_manager_leak_detection to false in your Selenium Chrome options to disable password leak detection and suppress the warning.

Problem

When running Selenium tests with recent versions of Chrome and Chromedriver (e.g., version 136+), entering “unsafe” (weak or reused) passwords in forms triggers a browser warning:

"This password has appeared in a data breach…"

This alert can break automated test runs, especially in CI/CD pipelines.

Solution

You can **disable Chrome’s password leak ...

Here are a few common patterns that will probably lead to flaky specs. If you notice them in your specs, please make sure that you have not introduced a flaky spec.

Using RSpec matchers

One rule of thumb I try to follow in capybara tests is using capybara matchers and not plain rspec matchers.

One example:

visit(some_page)
text_field = find('.textfield')
expect(text_field['value']).to match /pattern/

This can work, but is too brittle and flaky. match will not retry or synchronize the value of text_field.

The equivale...

There are three ways to define your own RSpec matchers, with increasing complexibility and options:

1) Use RSpec::Matchers.define

RSpec::Matchers.define :be_a_multiple_of do |expected|
  match do |actual|
    actual % expected == 0
  end
  
  # optional
  failure_message do |actual|
    "expected that #{actual} would be a multiple of #{expected}"
  end
  
  # optional
  failure_message_when_negated do |actual|
    "expected that #{actual} would not be a multiple of #{expected}"
  end
end

• This is automatically available i...

When an event listener on a DOM element throws an error, that error will be silenced and not interrupt your program.

In particular, other event listeners will still be called even after a previous listener threw an error. Also the function that emitted the event (like element.dispatchEvent() or up.emit()) will not throw either.

In the following example two handlers are listening to the foo event. The first handler crashes, th...

RubyMine comes with a nice way to grep through your project's files: The finder (ctrl + shift + f). Don't be discouraged about the notice 100+ matches in n+ files if your searched keyword is too general or widely used in your project.

RubyMine comes with a few ways to narrow down the resulting list, don't hesitate to apply those filters to speed up your search. Your keybinding might vary based on your personal settings.

File mask (alt + k)

If you already know the file extension of your ...

RSpec 3 has verifying doubles. This breed of mock objects check that any methods being stubbed are present on an instance of a given class. They also check methods aren't called with the wrong number of arguments.

This dual approach allows you to move very quickly and test components in isolation, while
giving you confidence that your doubles are not a complete fiction.

You should always prefer using a verifying double to using an old-school mock...

When you have a powerful machine with many CPU cores, you might run into an error like

ERR DB index is out of range (Redis::CommandError)

This is because Redis defaults to at most 16 databases (0 to 15) and running tests in parallel might exceed that (your tests might run on databases 1..n or 2..(n+1)).

You can increase that limit:

1. Get number of CPUs of your machine.

   nproc --all
   

2. Open up Redis configuration file.

   sudo vim /etc/redis/redis.conf
   

3. Find databases row and increase it, e.g. set to 32:

...

When you allow file uploads in your app, a user might upload content that hurts other users.

Our primary concern here is users uploading .html or .svg files that can run JavaScript and possibly hijack another user's session.

A secondary concern is that malicious users can upload executables (like an .exe or .scr file) and use your server to distribute it. However, modern operating systems usually warn before executing files that were downloaded from t...

RSpec allows you to mark a single Example/ExampleGroup so that only this will be run. This is very useful when using a test runner like guard.

Add the following config to spec/spec_helper.rb:

RSpec.configure do |config|
  # These two settings work together to allow you to limit a spec run
  # to individual examples or groups you care about by tagging them with
  # `:focus` metadata. When nothing is tagged with `:focus`, all examples
  # get run.
  config.filter_run_including :focus => true
  config.run_all_when_everything_filtere...

Within Capybara you most certainly use the #check- and #uncheck-method to (un)check checkboxes.
But there's one problem, if you want to test a custom styled checkbox, which hides its <input>-Tag:

• The methods cannot (un)check checkboxes without an visible <input>.
• The error message will be something like: Unable to find visible checkbox "Some label" that is not disabled

Solution 1

Use the keyword argument allow_label_click: true within the method call.
So instead of check('Some label'), use `check('Some label', allow...

We have a long-standing checklist for merge requests. However, it hardly matches the intricate requirements for design. This checklist fills the gap.

Before starting implementing, look at all designs: are there components similar to yours? Have they already been implemented? Can you build on this prior art when implementing yours?

Checklist: I confirm my design implementation

• has been tested manually by me
• adheres to the code style of the project (e.g. BEM)
• avoids "magic numbers" (don't say e.g. ...

When changing code in mailers, updating the corresponding mailer preview can be forgotten very easily.

Mailer previews can be tested like other code as well and I sometimes add the following tests to test suites:

# Make sure to require the previews
Dir[Rails.root.join('spec/mailers/previews/*.rb')].each { |file| require(file) }


ActionMailer::Preview.all.index_with(&:emails).each do |preview, mails|
mails.each do |mail|
    describe preview do
      specify "##{mail} works" do
        expect { preview.call(mail...

When you find yourself in the situation that you would like to define a custom matcher in your specs, but you do not want to define a global matcher since you need it only for your specific test, there are two ways to do it:

Custom matcher for a single group

If you're only going to include a matcher once, you can also use the matcher macro within an example group:

describe "group" do
  
  matcher :be_just_like do |expected|
    match {|ac...

Jasmine comes with two matchers that test for equality. The first is toBe:

expect(first).toBe(second)

toBe passes when first === second. Unfortunately this is useless for non-primitive values because JavaScript is a horrible language.

However, Jasmine comes with another matcher toEqual:

expect(first).toEqual(second)

This matcher behaves as a human would expect for types like the following:

• Arrays
• Objects
• Nested array/object constructs
• Regular expressions...

If a project ist configured to spawn CI runners for tests or deployment when pushing to the Repo, a habit of pushing WIP commits regularly may conflict with that.
Here are two solutions that allow you to keep pushing whenever you feel like it.

Special commit message

To skip a CI run, simply add [ci skip] or [skip ci] to your commit message. Example:

git commit -m "wip authentication [ci skip]"

Git push options (GitLab)

In addition to that, GitLab CI supports Git push options. Instead of changing your commit message, ...