Rails 3.1, RSpec: testing model validations

CONGRATULATIONS on you endeavor into TDD with ROR I promise once you get going you will not look back.

The simplest quick and dirty solution will be to generate a new valid model before each of your tests like this:

 before(:each) do
    @user = User.new
    @user.username = "a valid username"
 end

BUT what I suggest is you set up factories for all your models that will generate a valid model for you automatically and then you can muddle with individual attributes and see if your validation. I like to use FactoryGirl for this:

Basically once you get set up your test would look something like this:

it "should have valid factory" do
    FactoryGirl.build(:user).should be_valid
end

it "should require a username" do
    FactoryGirl.build(:user, :username => "").should_not be_valid
end

Oh ya and here is a good railscast that explains it all better than me:

good luck :)

---

UPDATE: As of version 3.0 the syntax for factory girl has changed. I have amended my sample code to reflect this.

An easier way to test model validations (and a lot more of active-record) is to use a gem like shoulda or remarkable.

They will allow to the test as follows:

describe User

  it { should validate_presence_of :name }

end