Notes: Josh McArthur

Access ActionView context in an RSpec test

I recently created a Presenter object to wrap around an ActiveStorage::Blob that I wanted to decorate with some presentation methods for things like a human file size and content type. The initialisation signature for my presenter looks like this: class MyPresenter < SimpleDelegator def initialize(obj, view_context) super(obj) @view_context = view_context end def human_file_size @view_context.number_to_human_size(byte_size, precision: 1) end # more presentation...

Access parent node with Capybara

Sometimes I’ll need to find an element in relation to another. An example of this is a link with a single icon element inside it: <a href="/example"><img src="icon.png" alt="Example Page" /></a> Because Capybara element finders can be chained (e.g. you can do find().find().find() to traverse down elements, the ability of XPath to traverse the DOM tree can be used to...

ActiveRecord::Base.update actually calls model setter methods

When an update method like @my_record.update(test_attr_1: "foo", test_attr_2: "bar") is called, my assumption was that those attributes immediately got passed to some ActiveRecord magic to update the record. Not true! Each attribute key calls the setter on the object - in this case, @my_record.test_attr_1=(new_value) and @my_record.test_attr_2=(new_value) would be called. This is neat because you can ‘redirect’ that attribute assignment to...

Handy Ruby shorthand for testing class ancestors

Today I was working on a method that had to take a string, and resolve it to a class. This method needed to perform some validation on the model class, to make sure it was a type we expected. My first iteration of this didn’t work - I expected that I could use Object#kind_of?, however this only works for testing...

Go offline with Capybara, Selenium and Chromedriver

There’s some preamble here. Jump to solution Recently, I’ve been working on a client project that needs to function offline. This means that I have a subset of tests where I need to change the connectivity status of the browser driving the tests to simulate being offline to make assertions that the application is behaving correctly. I already knew that...

Access browser console messages from a Capybara test

A very handy API I’ve stumbled across today: page.driver.browser.manage.logs.get(:browser) This returns an array of Selenium::LogEntry instances which have the expected properties - level, timestamp, and message. You can use standard Enumerable methods to filter the log entries down to the information relevant to you. For example, all error messages: page.driver.browser.manage.logs.get(:browser).select { |le| le.level == "SEVERE" }.map(&:message) => ["http://127.0.0.1:40539/madeup - Failed...

Use Foundation data attributes in a React functional component

I’ve been porting some previously server-rendered Rails templates to instead sit within a React application. This particular application uses Foundation Sites for base styles, and uses some of Foundation’s components which use Javascript to function - mostly basic stuff like data-dropdown, data-accordion, data-tabs. Foundation (still) uses jQuery for setting up these elements, and by default, initializes based on the ready...

What happens when I run 'rake db:migrate' in Ruby on Rails?

This post is written stepping through the most recent stable branch of Rails on Github: 6-1-stable. It may not remain up to date. Reading time: about 20 minutes Skip table of contents How is the ‘db:migrate’ rake task defined? The Rails gem includes ‘activerecord’ as a gem dependency: The activerecord gem adds it’s own ‘lib/` directory to Ruby’s load path:...

Preview Devise mailers

I use ActionMailer::Previews whenever I am implementing a transactional email. They’re a super handy way of working with email development, and I’ve even enabled them in UAT environments before so clients and designers can check the email easily. In many apps, nearly all the transactional email is actually sent by Devise, so I wanted to set up a ActionMailer preview...

Docker: You must use Bundler 2 or greater with this lockfile

Ever seen the error “You must use Bundler 2 or greater with this lockfile.” trying to build a Docker image from a Dockerfile that uses an older Ruby version? Even though you are gem installing the correct version of Bundler? It turns out that the Ruby Docker images set an environment variable called BUNDLER_VERSION, which Bundler will always try to...

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