AWS S3 Policies for Carrierwave

When you create IAM credentials and policies for your app, you should make sure that they have access to the resources that they need and not more than that!.

This way, if anyone gets access to those credentials, the impact of this leak is reduced to the resources associated with them (and not all the buckets in your S3 account)

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'Flaky' tests: a short story

One of the hardest failing tests to debug are those which fail randomly, also known as "flaky" tests. You write your test cases, you run the tests in your environment (in random order), and see them all pass. Afterwards, you push your code, your CI server runs them and one test fails.

This is not an uncommon scenario, and one too common when using integration tests which use JS, with Capybara-Webkit or Selenium. But if your failing test doesn't communicate with an external API, doesn't use JS, and passes locally, it can be a bit nerve-wracking.

After you have identified the failing test, and it still passes after running it locally, one way to figure out why it's failing is running its context multiple times.

To automate this process a bit, I like to use the following command:

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How to run multiple dependent builds on Circle CI

We all know the importance of having a CI tool integrated in your project. It allows you to run your entire test suite every time you want to merge a set of changes. If you have a core project and many projects that depend on it, you want to run the tests for the core project and the dependent projects at the same time. This article explains how you can do it with Circle CI.

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How to test a React app using capybara-webkit

I have been using the capybara-webkit gem for a while now since I first tried it out after making the switch from Capybara + Selenium.

Using capybara-webkit speeds up my Selenium tests due to its headless nature, and it's very straightforward. However, I had some trouble testing a Rails based React app.

In this post, I will explain how I worked around the issues that came up when trying to use capybara-webkit with React.

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Announcing AfipBill

If you live in Argentina and you ever use AFIP, you should already know that their platform is not the best in terms of user friendliness. We wanted to integrate OmbuShop with AFIP (using their API) in order to generate and print the bills for each seller. Unfortunately, there is no way to do this because the API doesn't generate a printable version (PDF) of the bill.

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How to use any gem in the Rails production console

How many times did you come across a great gem you wanted to try out in a production console, like benchmark-ips or awesome-print?

Be it for performance or for readability, sometimes it's nice to be able to try out something new quickly without going through a pull request + deployment process. This is possible by modifying the $LOAD_PATH Ruby global variable and requiring the gem manually.

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Present? vs Any? vs Exists?

When working on a Rails project, you may have seen present? calls on ActiveRecord relationships. This might feel natural, mostly because present? exists on all objects via ActiveSupport, so you expect the relationship to respond to it, but it's actually not a very good idea. If all we want to do is check if the scope returns any results from the database, there are better ways than using present?.

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Brief look at RSpec's formatting options

A few weeks ago, I noticed weird output in the RSpec test suite (~4000 tests) for a Rails application:

.............................................................................................unknown OID 353414: failed to recognize type of '<field>'. It will be treated as String  ...........................................................................................................................................

This Rails app uses a PostgreSQL database. After some Googling, it turns out that this is a warning from PostgreSQL. When the database doesn't recognize the type to use for a column, it casts to string by default.

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Tips for Writing Fast Rails: Part 1

Rails is a powerful framework. You can write a lot of features in a short period of time. In the process you can easily write code that performs poorly.

At Ombu Labs we like to maintain Ruby on Rails applications. In the process of maintaining them, adding features and fixing bugs, we like to improve the code and its performance (because we are good boy scouts!)

Here are some tips based on our experience.

Prefer where instead of select

When you are performing a lot of calculations, you should load as little as possible into memory. Always prefer a SQL query vs. an object's method call.

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Spy vs Double vs Instance Double

When writing tests for services, you may sometimes want to use mock objects instead of real objects. In case you're using ActiveRecord and real objects, your tests may hit the database and slow down your suite. The latest release of the rspec-mocks library bundled with RSpec 3 includes at least three different ways to implement a mock object.

Let's discuss some of the differences between a spy, a double and an instance_double. First, the spy:

[1] pry(main)> require 'rspec/mocks/standalone'
=> true
[2] pry(main)> user_spy = spy(User)
=> #<Double User>
[3] pry(main)> spy.whatever_method
=> #<Double (anonymous)>
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The Need for bin/start

Getting started with a new project should be as simple as possible, even for someone who is not technical. As a maintainer, you must make sure that anyone can clone your project and get it up and running in a few minutes.

After you clone a project, you should follow two steps:

  1. Setup
  2. Start
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Tips for upgrading from Rails 3.2 to 4.0

There are already quite a few guides in the wild to help with the upgrade of Rails 3.2 to Rails 4.0. The official Rails guide for upgrading from Rails 3.2 to 4.0 is very thorough. With the recent release of Rails 5.0, apps currently in production running Rails 3.2 should probably be updated to any stable Rails 4 release as soon as possible.

There is even an e-book about upgrading from Rails 3 to 4, which serves as a useful guide to make this upgrade easier, and also helps understand the advantages & disadvantages of this new (soon to be old) version.

However, if you're using any non-standard gems, you're mostly on your own. Some gems stopped being maintained before Rails 4 was released, as was the case with CanCan, a well known authorization library. After many open pull requests were left unmerged, CanCanCan was released. It is a community driven effort to have a semi-official fork of CanCan. It serves as a drop-in replacement for people who want to use CanCan after upgrading to Rails 4.

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Introducing Pecas: Dashboards for Freckle

At Ombu Labs we are big fans and happy customers of Freckle. We use their widget to track all the hours that we spend on client projects, open source development, and our own products.

Today I'm happy to introduce Pecas, time tracking leaderboards for Freckle! Pecas is an open source tool that integrates with your account and generates beautiful leaderboards per project and per teammate.

Here is a sample dashboard for all your projects:

A sample leaderboard in the Pecas web interface

On top of that, it will send you an email alert if you haven't tracked any hours during a work day. If it's a holiday, it won't bother you. :)

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A comprehensive guide to interacting with IMAP using Ruby

A few times in the past I've had to interact with IMAP via Ruby, and wrapping your head around its API is not so easy. Not only is the IMAP API a bit obscure and cryptic, but Ruby's IMAP documentation is not so great either.

Searching the internet for examples doesn't yield too many results, so I'll try to write down some of the things I've learned. The examples I'll show use Gmail as the target IMAP server.

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