By default parallel_tests will spawn as many test processes as you have CPUs. If you have issues with flaky tests, reducing the number of parallel processes may help.

Important

Flaky test suites can and should be fixed. This card is only relevant if you need to run a flaky test suite that you cannot fix for some reason. If you have no issues...

It is good programming practice to Don't Repeat Yourself (or DRY). In Ruby on Rails we keep our code DRY by sharing behavior by using inheritance, modules, traits or partials.

When you reuse behavior you want to reuse tests as well. You are probably already reusing examples in unit tests. Unfortunately it is much harder to reuse code when writing integration tests with Cucumber, where you need to...

PostgreSQL, unlike MySQL, treats strings as case sensitive in all circumstances.

This includes

• comparison with = and LIKE
• collision detection in unique indexes

Usually this is fine, but some strings (like emails and usernames) should typically be treated as case insensitive.

There are a few workarounds available:

• use the citext extension (not recommended)
• use ILIKE instead of LIKE
• use Postgres' lower() function
• add an index on lower(email)

Probably th...

View specs are a powerful tool to test several rendering paths by their cases instead of using a more costing feature spec. This is especially useful because they become quite convenient when used with Capybara::Node::Finders and Capybara::RSpecMatchers. This allows to wirte view unit specs as you can isolate specific part...

Basic configuration

Please keep this config simple. It should be a starting point for new developers learning Git.

[user]
  name = Your Name
  email = your.name@domain.com

[branch]
  sort = -committerdate
[color]
   ui = auto
[color "branch"]
  current = yellow reverse
  local = yellow
  remote = green
[color "diff"]
  whitespace = white reverse
  meta = blue reverse
  frag = blue reverse
  old = red
  new = green
[color "status"]
  added = green
  changed = yellow
  untracked = cyan
[interactive]
  singlekey = true # Do not requir...

This RailsCast demonstrated a very convenient method to activate VCR for a spec by simply tagging it with :vcr.

For RSpec3 the code looks almost the same with a few minor changes. If you have the vcr and webmock gems installed, simply include:

# spec/support/vcr.rb
VCR.configure do |c|
  c.cassette_library_dir = Rails.root.join("spec", "vcr")
  c.hook_into :webmock
end

RSpec.configure do |c|
  c.around(:each, :vcr) do |example|
    name = example.metadata[:full_descripti...

Rack::SteadyETag is a Rack middleware that generates the same default ETag for responses that only differ in CSRF tokens or CSP nonces.

By default Rails uses Rack::ETag to generate ETag headers by hashing the response body. In theory this would enable caching for multiple requests to the same resourc...

Git allows you to do a binary search across commits to hunt down the commit that introduced a bug.

Given you are currently on your branch's HEAD that is not working as expected, an example workflow could be:

git bisect start # Start bisecting
git bisect bad # Tag the revision you are currently on (HEAD) as bad. You could also pass a commit's SHA1 like below:
git bisect good abcdef12345678 # Give the SHA1 of any commit that was working as it should
# shorthand:
git bisect start <bad ref> <good ref>

Git will fetch a comm...

We use foreman to start all necessary processes for an application, which are declared in a Procfile. This is very convenient, but the outputs of all processes get merged together. Especially while debugging you might not want other processes to flood your screen with their log messages.

The following setup allows you to start Terminator in a split view with the Rails server running in the left pane and all remaining processes running via foreman in the right pane. It was heavily inspired by [this card](https://makandracards.com/makandr...

On some of our older projects, we use the mysql2 gem. Unfortunately, versions 0.2.x (required for Rails 2.3) and versions 0.3.x (required for Rails 3.2) can no longer be installed on Ubuntu 20.04. Trying this either leads to errors when compiling the native extension, or a segfaults when using it.

For Rails 4.2, mysql2 version 0.4.10 seems to work okay. If you still have issues, upgrade to 0.5.x, which should be compatible.

To install it, you have to switch the mysql2 gem to our fork. In your Gemfile, ...

Slow test suites are a major pain point in projects, often due to RSpec and FactoryBot. Although minitest and fixtures are sometimes viewed as outdated, they can greatly improve test speed.

We adopted a project using minitest and fixtures, and while it required some initial refactoring and establishing good practices, the faster test suite was well worth it! Stick with me to explore how these tools might actually be a good practice.

So, why is this setup faster? Partially, it's because minitest is more lightweight than RSpec, which...

Capybara-screenshot can automatically save screenshots and the HTML for failed Capybara tests in Cucumber, RSpec or Minitest.

Requires Capybara-Webkit, Selenium or poltergeist for making screenshots. They're saved into $APPLICATION_ROOT/tmp/capybara

The attached files contain config for cucumber integration and a Then show me a screenshot step.
If your project uses Spreewald, you can use its Then show me the page step instead.

Inclu...

tl;dr
You can use attribute? as shorthanded version of attribute.present?, except for numeric attributes and associations.

Technical Details

attribute? is generated for all attributes and not only for boolean attributes.

These methods are using #query_attribute under the hood. For more details you can see ActiveRecord::AttributeMethods::Query.

In most circumstances query_attribute is working like attribute.present?. If your attribute is responding to :zero? then you have to be aware that `query_attri...

• To retrieve only unique combinations of the selected attributes: You can omit rows, where all selected columns are equal with the DISTINCT statement.
• To retrieve the group wise maximum of certain columns: You can keep only one record for each group with the DISTINCT ON statement, to omit equal rows within each specified group.

Use case

You have a query where you want only one record for a set of specifically ordered attributes.

How to use?

Let's say we look at the example how to query only the latest post for each user:
...

This should be fixed in the latest LTS-branches of our mysql2 fork, 0.2.x-lts and 0.3.x-lts.

Use

gem 'mysql2', git: 'https://github.com/makandra/mysql2', branch: '0.2.x-lts' # for Rails 2.x
gem 'mysql2', git: 'https://github.com/makandra/mysql2', branch: '0.3.x-lts' # for Rails 3.x

in your Gemfile, and do a

bundle update mysql2

Background

mysql2 used to check that the client library used at runtime actually matches the one it was compiled against. However, at least on Ubunt...

Note: For PostgreSQL you should use advisory locks. For MySQL we still recommend the solution in this card.

If you need to synchronize multiple rails processes, you need some shared resource that can be used as a mutex. One option is to simply use your existing (MySQL) database.

The attached code provides a database-based model level mutex for MySQL. You use it by simply calling

Lock.acquire('string to synchronize on') do
  # non-th...

When you have string contents (e.g. a generated binary stream, or data from a remote source) that you want to store as a file using Carrierwave, here is a simple solution.

While you could write your string to a file and pass that file to Carrierwave, why even bother? You already have your string (or stream).
However, a plain StringIO object will not work for Carrierwave's ActiveRecord integration:

>> Attachment.create!(file: StringIO.new(contents))
TypeError: no implicit conversion of nil into String

This is because Carrierwav...

The ActiveSupport::BroadcastLogger allows you to log to multiple sinks. You know this behavior from from the rails server command, that both logs to standard out and the log/development.log file.

Here is an example from the ActiveSupport::BroadcastLogger API:

stdout_logger = ActiveSupport::Logger.new(STDOUT)
file_logger = ActiveSupport::Logger.new("development.log")
broadcast = ActiveSupport::BroadcastLogger.new(stdout_logger, file_logger)

broadcast.i...

Example

I, [2024-01-21T06:22:17.484221 #2698200]  INFO -- : [4cdad7a4-8617-4bc9-84e9-c40364eea2e4] test
I, [2024-01-21T06:22:17.484221 #2698200]  INFO -- : [4cdad7a4-8617-4bc9-84e9-c40364eea2e4] more
I, [2024-01-21T06:22:17.484221 #2698200]  INFO -- : [6e047fb3-05df-4df7-808e-efa9fcd05f87] test
I, [2024-01-21T06:22:17.484221 #2698200]  INFO -- : [6e047fb3-05df-4df7-808e-efa9fcd05f87] more
I, [2024-01-21T06:22:17.484221 #2698200]  INFO -- : [53a240c1-489e-4936-bbeb-d6f77284cf38] nope
I, [2024-01-21T06:22:17.484221 #2698200]  INFO -- ...

OpenAI is currently limiting the Audio generating API endpoint to text bodies with a maximum of 4096 characters.
You can work around that limit by splitting the text into smaller fragments and stitch together the resulting mp3 files with a CLI tool like mp3wrap or ffmpeg.

Example Ruby Implementation

Usage

input_text = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Mi eget mauris pharetra et ultrices neque."
output_mp3_path = Rails.root.join("tts/ipsum...

Webpack is the future. We're using it in our latest Rails applications.

For tests, we want to compile assets like for production.
For parallel tests, we want to avoid 8 workers compiling the same files at the same time.
When assets did not change, we do not want to spend time compiling them.

Here is our solution for all that.

Its concept should work for all test suites.

Copy the following to config/initializers/webpacker_compile_once.rb. It will patch Webpacker, but only for the test environment:

# Avoid hardcoded asset host...

If you ever need to restore exact records from one database to another, Marshal might come in handy.

Marshal.dump is part of the ruby core and available in all ruby versions without the need to install anything. This serializes complete ruby objects including id, object_id and all internal state.

Marshal.load deserializes a string to an object. A deserialized object cannot be saved to database directly as the the dumped object was not marked dirty, thus rails does not see the need to save it, even if the object is not present in...

When using Rails to truncate strings, you may end up with strings that are still too long for their container or are not as long as they could be. You can get a prettier result using stylesheets.

The CSS property text-overflow: ellipsis has been around for quite a long time now but since Firefox did not support it for ages, you did not use it. Since Firefox 7 you can!

Note that this only works for single-line texts. If you want to truncate tests across multiple lines, use a JavaScript solution like...

Rails' ActiveSupport::TimeWithZone objects have both a timezone code and offset, e.g. Thu, 28 Mar 2019 16:00:00 CET +01:00. Ruby's stdlib TZInfo also has time zones, but with different identifiers.
Unfortunately, not all timezone codes can be used to parse strings or to move time objects into another time zone.

Some timezone codes like CET are supported by ActiveSupport extensions like String#in_time_zone, while many codes will actually not work:

>> '2019-03-01 12:00'.in_time_zone('PST')
ArgumentError (Invalid Timezone: PST)
...