The last lesson covered unit testing and now we will move into model testing. Here you will get an idea of how to test within Rails for model testing as well as a deeper dive of how to structure these tests.
This section contains a general overview of topics that you will learn in this lesson.
- What are model tests?
- How do I run a model test?
- How to structure model testing?
A model test is a unit test in the context of Ruby on Rails. When testing our models we usually want to focus on testing the business logic. Essentially what goes on behind each model that enables the user experience to work correctly. This could mean ensuring promotion tickets prices are correct, only correct form data is accepted, custom user verification etc. It's important to note that each model should have it's own file in the spec/models file. This is helpful for keeping your model tests organized and readable.
The first tool that we are going to go over for setting up the data is factory bot. Factory bot is a gem that you can use to set up test data and create necessary data for your tests. Adding Factory bot is similar to adding other testing gems. Add the following line to the to the following section in your Gemfile.
group :development, :test do
gem "factory_bot_rails" #Add this line.
end
Then in your terminal enter bundle install to the terminal where it will install the gem. Now we need to move into setting up our test configuration to utilize Factory bot. First were going to navigate to spec/support/factory_bot.rb and add the following configuration.
RSpec.configure do |config|
config.include FactoryBot::Syntax::Methods
end
Make sure to require this file in rails_helper.rb. While you can require the file by adding require support/factory_bot to the top of the file. Rails also provides this in the commented out line Dir[Rails.root.join("spec/support/**/*.rb")].each { |f| require f } which enables you to load all of the support files when booting up. This is useful for not having to manually add all of the support files and avoids issues if you forget to add a file for example.
The last thing you might be wondering is how the test database clears itself in between it's tests. Rail's does this automatically for you, however if Rail's is not doing it for you make sure your following the instructions in the rails_helper.rb file and make sure to ask in the Discord first! If you are interested, you can learn more about database cleaning in the additional resources.
Below is an example of a user factory. Notice that the factory will be a User class based off of the name of your factory. You can also define as many attributes as you want and it can be useful to focus on adding only the attributes you are testing and adding them as need be.
# This will guess the User class
FactoryBot.define do
factory :user do
first_name { "John" }
last_name { "Doe" }
admin { false }
end
end
When creating a factory bot record you have the choice of using the create(:user) which returns a saved instance of the object from your database or build(:user) which returns an unsaved instance of an object.
In the following example one of the things we often see when users sign up is that sites will ask for an email to send a user notifications for example. RSpec can help you test this by utilizing model tests. Let's take a look at what a requiring the presence of a user email would look like in a model and the corresponding tests.
class User < ApplicationRecord
validates :email, presence: true
end
In the above code validates will check for the presence of the email. By using validates the model will check the following conditions which in this case is that the email is present when the record is created. That then brings us to the following RSpec test where we will write the context and what we expect the outcome to be.
RSpec.describe User, type: :model do
describe '#valid?' do
context "when the user does not have an email address" do
user = build(:user)
it "will not be valid" do
expect(user.valid?).to be false
end
end
context "when the user has an email address" do
user = build(:user, email_address: "jdoe@example.com")
it "will be valid" do
expect(user.valid?).to be true
end
end
end
end
One thing to note is that we have two tests. We want to test both the successful conditions while having a separate test for rejecting the invalid condition. The other thing to note is that you can set attributes when creating a factory record as well rather than going back to the factory file. The Factory bot repository has excellent information for diving in deeper and it's highly recommended to read through it to understand factory bot better.
This section contains questions for you to check your understanding of this lesson on your own. If you’re having trouble answering a question, click it and review the material it links to.
- What are model tests?
- How would I create a factory to use in my tests?
- What are some examples of testing business logic?
This section contains helpful links to related content. It isn't required, so consider it supplemental.
- For an example of a model test and having a useful resource. You can visit code with Jason.
- For an alternative if RSpecs built in database cleaner isn't working for testing. You can find it here.
- A resource for going over some of the best practices for tests.