Create only the data you need

If you have ever worked in a medium size project(but also in small ones), test suites can be heavy to run. To solve this problem, it’s important not to load more data than needed. Also, if you think you need dozens of records, you are probably wrong.

• Good

describe "User" do
  describe ".top" do
    before { FactoryGirl.create_list(:user, 3) }
    it { expect(User.top(2)).to have(2).item }
  end
end

Use factories and not fixtures

This is an old topic, but it’s still good to remember it. Do not use fixtures because they are difficult to control, use factories instead. Use them to reduce the verbosity on creating new data.

• Bad

user = User.create(
  name: 'Genoveffa',
  surname: 'Piccolina',
  city: 'Billyville',
  birth: '17 Agoust 1982',
  active: true
)

• Good

user = FactoryGirl.create :user

One important note. When talking about unit tests the best practice would be to use neither fixtures or factories. Put as much of your domain logic in libraries that can be tested without needing complex, time consuming setup with either factories or fixtures. Read more in this article.

Mock or not to mock

There’s a debate going on. Do not(over) use mocks and test real behavior when possible. Testing real cases are useful when updating your application flow.

• Good

# simulate a not found resource
context "when not found" do
  before { Resource.stub(:where).with(created_from: params[:id]).and_return(false) }
  it { should respond_with 404 }
end

Mocking makes your specs fater but they are difficult to use. You need to understand them well to use them well. Read more about.