Rails%203%20In%20Action

42 CHAPTER 2 Testing saves your bacon
When /^I take out (\d+)$/ do |amount|
@account.balance -= amount.to_i
end
That makes this third step pass, because you’re subtracting a Fixnum from a Fixnum.
When you run this feature, you’ll see that this step is definitely passing and the final
step is now pending:
Scenario: Taking out money
Given I have an account
And it has a balance of 100
When I take out 10
Then my balance should be 90
TODO (Cucumber::Pending)
This final step asserts that your account balance is now 90. You can implement it in
features/step_definitions/account_steps.rb, as shown in the following listing.
Then /^my balance should be (\d+)$/ do |amount|
@account.balance.should eql(amount.to_i)
end
Here you must coerce the amount variable into a Fixnum again so you’re comparing a
Fixnum with a Fixnum. With this fourth and final step implemented, your entire scenario
(which also means your entire feature) passes:
Scenario: Taking out money
Given I have an account
And it has a balance of 100
When I take out 10
Then my balance should be 90
1 scenario (1 passed)
4 steps (4 passed)
As you can see from this example, Cucumber allows you to write tests for your code in
syntax that can be understood by developers, clients, and parsers alike. You’ll see a lot
more of Cucumber when you use it in building your next Ruby on Rails application.
2.4 Summary
Listing 2.32 features/step_definitions/account_steps.rb
Listing 2.33 features/step_definitions/account_steps.rb
This chapter demonstrated how to apply TDD and BDD principles to test some rudimentary
code. You can (and should!) apply these principles to all code you write,
because testing the code ensures it’s maintainable from now into the future. You don’t
have to use the gems shown in this chapter to test your Rails application; they are just
preferred by a large portion of the community.
You’ll apply what you learned in this chapter to building a Rails application from
scratch in upcoming chapters. You’ll use Cucumber from the outset by developing