Getting started with BDD / TDD (Rails / Rspec)

Question

I'm just starting to learn the practice of BDD / TDD (world rejoices, I know). One of the things that I struggle with at this point is which tests are actually worth writing. Let's take these set of tests which I started for a model called Sport:

Factory.define :sport do |f|
  f.name 'baseball'
end


require 'spec_helper'

describe Sport do

  before(:each) do
    @sport_unsaved = Factory.build(:sport)  # returns an unsaved object
    @sport_saved = Factory.create(:sport) # returns a saved object
  end

  # Schema testing.
  it { should have_db_column(:name).of_type(:string) }
  it { should have_db_column(:created_at).of_type(:datetime) }
  it { should have_db_column(:updated_at).of_type(:datetime) }

  # Index testing.

  # Associations testing.
  it { should have_many(:leagues) }

  # Validations testing.
  it 'should only accept unique names' do
    @sport_unsaved.should validate_uniqueness_of(:name)
  end

  it { should validate_presence_of(:name) }

  it 'should allow valid values for name' do
    Sport::NAMES.each do |v|
      should allow_value(v).for(:name)
    end
  end

  it 'should not allow invalid values for name' do
    %w(swimming Hockey).each do |v|
      should_not allow_value(v).for(:name)
    end
  end

  # Methods testing.

end

Few specific questions that I have:

Is it worth testing that the association sport.leagues returns a non-blank value?
How about a test that ensure the model is invalid if a name is not specified?
How about a test to make sure that a valid record is created and doesn't have any validation errors?

I could go on. Ideally, there would be some hard and fast rules I could follow to guide my testing effort. But I am guessing this comes with experience and good ole' pragmatism. I've thought about reading through the source code of several gems such as the rails core to gain a better understanding of what's worth testing and what isn't.

Any advice you experienced testers out there could offer?

Dave Newton Dave Newton · Accepted Answer · 2012-01-10T15:45:06

Not if you're only re-testing Rails behavior.
Yes--it's part of model validation and a requirement, why not make sure the requirement is met?
Testing your assumptions regarding the save process is a good idea, and if there are any lifecycle listeners/observers they may not be fired until the save.

The Rails core tests won't help you decide what's a good idea to test in an application.

Getting started with BDD / TDD (Rails / Rspec)

2 Answers