How to make changes to a Ruby gem (as a Rails developer)
At makandra, we've built a few gems over the years. Some of these are quite popular: spreewald (475k downloads), active_type (330k downloads), and geordi (210k downloads) for example (numbers from 2018).
Developing a Ruby gem is different from developing Rails applications, with the biggest difference: there is no Rails. This means:
- no defined structure (neither for code nor directories)
- no autoloading of classes, i.e. you need to
requireall files yourself - no [
active_support](https://api.rubyonrails.org/classes/ActiveSupport.ht…
Cucumber features as documentation
Cucumber allows for prose in features and scenarios. Example:
Feature: Cancel account
There are several ways to cancel a user account. Admins need to
do it in complex cases, but normally, users can do it themselves.
Scenario: User cancels his own account
Users should be able to cancel an account themselves, so the
admins do not need to do it.
Given a user account for "willy@astor.de"
When I sign in as "willy@astor.de"
And I follow "Cancel account"
Then I should see "Account canceled"
B…
How to fill in multiple lines in a textarea with cucumber
If you want to fill in textareas with multiple lines of text (containing line breaks) you can use Cucumber's docstrings:
And I fill in "Comment" with:
"""
This is a long comment.
With multiple lines.
And paragraphs.
"""
The step definition is part of the spreewald gem
Find an ActiveRecord by any column (useful for Cucumber steps)
The attached patch lets you find a record by a string or number in any column:
User.find_by_anything('carla')
User.find_by_anything('email@domain.de')
User.find_by_anything(10023)
There's also a bang variant that raises ActiveRecord::NotFound if no record matches the given value:
User.find_by_anything!('carla')
Boolean and binary columns are excluded from the search because that would be crazy.
I recommend copying the attachment to features/support/find_by_anything.rb, since it is most useful in Cucumber step …
How to update a single gem conservatively
The problem
Calling bundle update GEMNAME will update a lot more gems than you think. E.g. when you do this:
bundle update cucumber-rails
… you might think this will only update cucumber-rails. But it actually updates cucumber-rails and all of its dependencies. This will explode in your face when one of these dependencies release a new version with breaking API changes. Which is all the time.
In the example above updating cucumber-rails will give you Capybara 2.0 (because capybara is a dependency of `cucumber-rail…
Jasmine: Adding custom matchers
Definition
A matcher is a function that returns an object with a compare key. Usually it is registered with beforeEach:
beforeEach ->
jasmine.addMatchers
# Example matcher
toBeAnything: ->
compare: (actualValue, matcherArguments...) ->
# Do some computations here ...
# Return whether the actualValue matches the expectation
pass: true
Usage
expect(actualValue).toBeAnything(matcherArguments...)
When a matcher is invoked, Jasmine will call its compare() fu…
Grep through the DOM using the Capybara API
When your Cucumber feature needs to browse the page HTML, and you are not sure how to express your query as a clever CSS or XPath expression, there is another way: You can use all and find to grep through the DOM and then perform your search in plain Ruby.
Here is an example for this technique:
Then /^I should see an image with the filename...
Firefox: Focus-sensitive Selenium tests do not work reliably in parallel test execution
This is a problem when using Selenium with Firefox. We recommend using ChromeDriver for your Selenium tests.
Firefox will not trigger focus/blur events when its window is not focused. While this makes sense in standard usage, it breaks in parallel test execution.
Please do not rely on focus events in your tests. The linked card has an example of how to build passing tests that deal with focus/blur events.
Nested Spreewald patiently blocks are now patient
In Spreewald 1.10.4+, nested patiently blocks are now patient.
Here is an example:
patiently do
outer_code
patiently do
inner_code
end
end
On spreewald 1.11.2+ the inner block will wait for the full configured wait time (by default 5 seconds). The outer patiently block would now be out of time, but it will always be retried at least a second time. This behavior allows with_scope to be patient, and it must be patient, as explained below.
In versions 1.10.4 - 1.11.1, inner blocks would keep giving the ou…
How to stub class constants in RSpec
Hint: There's another card with this helper for Cucumber features.
Sometimes you feel like you need to stub some CONSTANT you have defined in an other class. Since actually constants are called constants because they're constant, there's no way to easily stub a constant.
Here are three solutions for you.
Easiest solution
Rethink! Do you really need CONSTANT = %w[foo bar] to be constant? In many cases, setting it as a…
How to control Chromedriver using curl
Here is how to use Chromedriver without libraries like selenium-webdriver. This can be useful for debugging.
The following example visits a web page and reads the a headline's text contents.
-
Create a session:
curl -XPOST http://localhost:9515/session -d '{"desiredCapabilities":{"browserName":"chrome"}}'You will get a JSON response containing lots of information about your Chrome session, including a
sessionId. Use this to send any future commands to your chromedriver session.{"sessionId":"your-session...