This is part of an ongoing series of posts about how to get started writing tests for Ruby on Rails. The series begins with an introduction and overview of the ideas behind testing.

In previous sections, we learned to unit test the ActiveRecord associations and validations in our classes. Both are extremely common and appear in most Rails models. While less common, attribute definition methods and callbacks are still used somewhat frequently and are worth learning to test.

Hopefully by now your knowledge and confidence about writing tests is growing!

Attribute Definition Methods

When I refer to attribute definition methods, a classification I made up, I am referring to the methods that define and describe attributes in our model. There are two kinds. First, there are methods in the Ruby language that define attribute reader and writer methods: attr, attr_accessor, attr_reader, and attr_writer. Second, there are methods in the Rails framework that limit the access to attributes: attr_accessible, attr_protected, and attr_readonly.

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This is part of an ongoing series of posts about how to get started writing tests for Ruby on Rails. The series begins with the introduction and overview of the ideas behind testing.

Now that we have unit tests to insure that our models are related properly, we are ready to test our the validations in our models.

There are two approaches to testing your validations. It will be useful to examine both techniques because it will help you to write better tests overall. First, we need to write tests that confirm the code we have in place is working properly—as we have done thus far. Second, we need to think about special cases that we might not have coded into our validations already. This is where writing tests can really improve your code, and validations are a great place to see it in action.

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This is part of an ongoing series of posts about how to get started writing tests for Ruby on Rails. The series begins with the introduction and overview of the ideas behind testing.

Unit Testing ActiveRecord

In the unit tests we wrote previously, we tested everything in the class. The rule of thumb was that everything needs to be tested. That has not changed now that we are working with ActiveRecord—each method still needs a test.

But what testing should be done on the basic database CRUD (Create, Read, Update, Delete)? After all, that is what is most different about classes that inherit from ActiveRecord, right? It may surprise you to learn that we do not need to test basic CRUD.

Why not? ActiveRecord handles all of our database activity for us. It knows how to connect to the database, how to create, find, read, update, delete, use conditions and sort. That is the reason why we are using a framework like Rails to begin with: because we can inherit all that ActiveRecord goodness without having to rewrite it ourselves. We can trust that ActiveRecord will do its job correctly.

photo by Tomás Castelazo

That is not blind trust—ActiveRecord has its own unit tests that the core Rails team uses to insure that it works properly. Therefore we can assume that everything our class inherits from ActiveRecord is solid and tested. It was unit tested before we installed it. We just need to focus on our code in the subclass.

The corollary to “Test Everything” is: “If it is code you added, it is code you need to test.”

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This is part of an ongoing series of posts about how to get started writing tests for Ruby on Rails. The series begins with the introduction and overview of the ideas behind testing.

Fixtures

In the most general terms, a test fixture is an environment for running tests which is in a fixed state (i.e. it is ‘fixed’). While the term is primarily associated with software development, it applies to any testing environment.

Think back to our car battery example for a moment. If we unit test the battery inside the car, there is a chance that our testing environment will throw off the results. Ideally, we would remove the battery from the car and put it in a test environment that we know is stable, thereby removing as many variables and potential sources of error as possible. Then our unit test results should be predictable, accurate and repeatable. The environment we put the battery in—the meters, the wires attached to it, the amount of voltage we put in or out, etc.—is the test fixture. It will stay the same during each test we run on the battery.

You have encountered fixtures in other contexts before without knowing it. A race track is an example of fixture. The cars and drivers racing around it are different, but the pavement and curves are the same for everyone. When a race (which is essentially a benchmark test) pits the cars against each other, the fixtures are important in ensuring that the winner is meaningful. Everyone faces the same conditions, yet one car will be faster than the rest. If every car raced on a different course the race results would be meaningless. Sports and competitive events are filled with examples of fixtures—generally known as “having a level playing field.”

The idea is to fix the environment so that the environment will not skew the results.

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This is part of an ongoing series of posts about how to get started writing tests for Ruby on Rails. The series begins with the introduction and overview of the ideas behind testing.

Setting Up for Unit Testing ActiveRecord Models

In the previous section, we saw that running unit tests inside the Rails framework is not that different from running tests outside it. We have learned how to test the Car class in both Ruby and Rails. But Car does not inherit from ActiveRecord::Base (or, if yours did, our tests did not probe any ActiveRecord traits). Let’s see how our unit tests would be different if our class was using ActiveRecord to store instances in a database.

For this example, we will keep using the same sample application, but we will move away from cars and create two new classes: Winery and Wine. Each winery will produce several different wines. We start by using script/generate to create our two models.

The generator will create the model, a migration, a skeleton for your unit test and even a fixture file we will use later, all in one easy step. You do not need to worry about creating controllers, scaffolding or views. They are irrelevant for unit testing.

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This is part of an ongoing series of posts about how to get started writing tests for Ruby on Rails. The series begins with the introduction and overview of the ideas behind testing.

Unit Tests + Rails

After so much discussion of unit testing in Ruby you are probably anxious to start applying your new-found skills to a Rails application. The good news is that everything you have learned so far is directly applicable to testing in Rails.

When you first create a new Rails application (e.g. rails sample_app), a folder called ‘test’ is created in your application’s root directory. This is the folder where all of your test code will reside.

As you would expect, we will be putting all of our application’s unit tests inside the subfolder called ‘unit’. At first that folder will be empty. When a new model is generated, the generator script will also create a skeleton for unit testing that model.

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This is part of an ongoing series of posts about how to get started writing tests for Ruby on Rails. The series begins with the introduction and overview of the ideas behind testing.

Testing the colors Method

Now that we have examined the thought process behind writing tests, I will move more quickly through test_colors and test_full_name. test_colors is simple: invoking colors on the class Car will return an array of colors. How much and what kind of testing this requires is up to you and really depends on your application’s usage. Here are some examples:

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This is part of an ongoing series of posts about how to get started writing tests for Ruby on Rails. The series begins with the introduction and overview of the ideas behind testing.

Unit Testing Classes and Instances

Any Ruby code can be tested with TestUnit. Working with classes and instances of objects is no different. Let’s create definition for a Car class (keeping with the car theme from the last section). Then we can write tests that will test the Car class. We will also spend some time considering what we should test and how we can test it.

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This is part of an ongoing series of posts about how to get started writing tests for Ruby on Rails. The series begins with the introduction and overview of the ideas behind testing.

Unit Testing

I am going to cover several types of tests over the course of this tutorial: unit tests, functional tests, integration tests. I will start with unit tests. Unit tests are a good way to introduce the subject of testing and, if you already have a working Rails application, they are the first tests you should consider adding. Think of unit tests as our first testing layer, a foundation for the other layers.

Unit testing is a testing technique to validate that individual “units” of code are working properly. A “unit” refers to the smallest testable part of the code. When unit testing, we are not interested in how all the units fit together, just in make sure that each unit is functioning properly on its own.

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For some time, I’ve been wanting to teach how to get started writing tests for Ruby on Rails. Eventually I’d like to do a video training on the subject, but until then I’ve decided to write a series of blog posts as a tutorial.

Everyone agrees that testing is important, yet a small percentage of developers actually write tests. That’s understandable because there is a lot to learn when first starting with Ruby on Rails: installation, Ruby, the MVC framework, Rails, ActiveRecord, migrations, validations, routes, pagination, plug-ins, deployment… There’s more than enough to keep beginners busy during their first few projects. Testing requires learning yet another skill for something that seems like it can be put off until later. After all, you just want to get the site built, right?

Experienced developers often preach to beginners how important it is to test. I’ve even heard it said: “You are not a professional developer unless you write tests.” That is simply not true. You can write great applications, have lots of clients and make lots of money without writing tests. There are thousands of professional developers who don’t. But what I think they really mean by that statement is: Once you start writing tests, you’ll reap a lot of benefits (saving time and writing better code), take your programming to another level, and have a competitive edge over developers who don’t write tests. And who doesn’t want to save time and write better code???

But how do you get there? If you are a Ruby on Rails beginner, focus on the essentials first. Write an application or two. You can start writing tests from the beginning, but I think it’s best if you learn to program in Ruby and have a solid understanding of what Rails is doing first. After you have the fundamentals down, you’ll be ready to learn to write tests. Don’t worry, it’s not as difficult as it might seem. I’m going to walk you through the process step-by-step. (It’ll be an ongoing project spread out over many blog posts.)

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