Tag: Scala

Automating integration tests with docker-compose and Makefile

~ Luciano Molinari ~ 1 Comment

I remember a few years ago the adventure developers would face in order to run integration tests on their machines, as they had to install and configure external services (usually some RDBMS and application servers), use some shared testing environment, or something similar. Nowadays, docker has simplified a lot that situation, once external dependencies are available as images that can be used in any environment.

However, today it’s rather common to see applications that rely on many more external services than before, like different databases. Docker compose is another tool in the docker universe that helps applications to define all of their external dependencies, making much easier and cleaner to run (mainly) integration tests. But sometimes, only these tools are not enough. One still needs to start the containers, run some initialisation steps (like creating database, messaging topics, etc) and only then run their tests. For that, one can still rely on a quite old but popular tool: Makefiles.

In this article we’ll use a very simple application that has a repository class responsible for adding and retrieving entities in/from a MySql database. We also want to create a few integration test cases for this class using a real MySql server. The application is written in Scala and managed using SBT, but don’t get distracted by these details. The ideas shown here can be applied to any other programming language/building tool, as they are more related to the infrastructure than to the application itself.

Without further ado, let’s start!

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Testing Future Objects with ScalaTest

~ Luciano Molinari ~ Leave a comment

Scala provides nice and clean ways of dealing with Future objects, like Functional Composition and For Comprehensions. Future objects are a great way of writing concurrent and parallel programs, as they allow you to execute asynchronous code and to extract the result of it at some point in the future.

However, this type of software requires a different mindset in terms of reasoning about it, be it while writing the main code or while thinking about testing it. This article will focus primarily in testing this type of code and, for this, we’ll be looking into ScalaTest, one of the best and most popular testing frameworks in the Scala ecosystem (If you want to take a look at running integration tests with Docker/Docker-compose and Makefiles, take a look at this post).

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Building a service using Akka HTTP and Redis – Part 2 of 2

~ Luciano Molinari ~ 1 Comment

In this second and last part, we’ll see how to use Akka HTTP to create RESTful Web Services. The idea is to expose the operations defined in the first part of this article, using HTTP and JSON.

Akka HTTP implements a full server/client-side HTTP based on top of Akka Actors. It describes itself as “a more general toolkit for providing and consuming HTTP-based services instead of a web-framework“. One interesting aspect is that it provides different abstraction levels for doing the same thing in most of the scenarios, i.e., provides high and low level APIs. Akka HTTP is pretty much the continuation of the Spray Project and Spray’s creators are part of Akka HTTP team. In our example, we’ll be using the high level Routing DSL to expose services, which allows routes to be defined and composed by directives. We’ll also use the Spray Json project to provide the infrastructure needed to use JSON with Akka HTTP.

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Building a service using Akka HTTP and Redis – Part 1 of 2

~ Luciano Molinari ~ 1 Comment

This article is split in 2 parts and it aims to show how to create a small application (or a microservice if you prefer) using Akka HTTP (Scala) and Redis database.The application is very focused and provides means for a customer to be added, removed and retrieved.

In terms of technologies/tools/libs, the following ones will be used:

  • Scala
  • SBT
  • Akka HTTP/Akka HTTP Json Support/Akka HTTP Test kit
  • Rediscala
  • Scalatest
  • Redis database

In this first part, we’ll focus on the layer responsible for communicating with Redis, while the second part will focus on Akka HTTP.

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Reading and processing a CSV file with Scala

~ Luciano Molinari ~ Leave a comment

In this article we will create a simple but comprehensive Scala application responsible for reading and processing a CSV file in order to extract information out of it.

Although simple, this app will touch in the following points:

  • Creating an application from scratch using SBT
  • Usage of traits, case class and a few collection methods
  • Usage of scalatest framework to write unit tests

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