Advanced Testing Techniques with Ruby on Rails

Advanced Testing
RubyEnRails Conference ’09

Goals

• Share our experiences about testing
• Make you start thinking critical about testing
like an advanced tester
• Unit testing with RSpec
• Integration testing with Cucumber

Student Master of
Computer Science

@edwin_v Edwin Vlieg
Course: Testing
Techniques

Student Master of
Computer Science

@edwin_v Edwin Vlieg
Course: Testing
5
Techniques

• Web application written in Ruby on Rails
• Create and send invoices online
• More than 16.000 invoices sent
• Short development cycle: 2 months
• API for web developers
• More info: www.moneybird.com

“A donkey does not knock
himself to the same stone twice”

It is okay to write code that doesn’t work...

But never ‘cap deploy’ it!

Software testing
... is a technical process performed by executing
a product in a controlled environment, following
a speciﬁed procedure, with the intent of
measuring the quality of the software product by
demonstrating deviations of the requirements.

Unit testing

• Test individual units of code
• A unit is the smallest testable piece of
code: methods of classes
• E.g. methods of controllers and models

TDD / BDD

Test before you write a single piece of code

TDD / BDD

Test before you write a single piece of code

Can be a nice approach, but requires a lot of
discipline and might not ﬁt your needs,
but know how it can help you!

Example
Recurring invoices

Calculate the next occurence of a recurring invoice.

Start date Current occurence Next occurence

Jan Febr Mar Apr May

First version

def next_occurence(today)
today + 1.month
end

RSpec-t

describe "Date calculation" do
it "should return the next month" do
next_occurence(Date.parse('2009-01-01')).should ==
Date.parse('2009-02-01')
end
end

You ain’t testing this,
because it looks too easy

Customer: “I want to bill every
last day of the month”

‘2009-01-31’ + 1.month = ‘2009-02-28’
‘2009-02-28’ + 1.month = ‘2009-03-28’
‘2009-01-31’ + 2.months = ‘2009-03-31’

Boundary Value Analysis
Find the boundaries of the input and test them

Boundary Value Analysis
Find the boundaries of the input and test them

Start Current Next
2009-01-31 2009-01-31 2009-02-28
2009-01-31 2009-02-28 2009-03-31
2009-01-31 2009-03-31 2009-04-30
2009-01-30 2009-01-30 2009-02-28
2009-01-30 2009-02-28 2009-03-30
2009-01-30 2009-03-30 2009-04-30
2009-01-29 2009-01-29 2009-02-28
2009-01-29 2009-02-28 2009-03-29
2009-01-29 2009-03-29 2009-04-29
2009-01-28 2009-01-28 2009-02-28
2009-01-28 2009-02-28 2009-03-28
2009-01-28 2009-03-28 2009-04-28

Create tests for all boundary values...

...and improve your code!

The solution

def self.calculate_next_occurence(start_date, current_date)
next_date = current_date + 1.month
while start_date.day != next_date.day and
next_date != next_date.end_of_month
next_date = next_date.tomorrow
end
next_date
end

“Testing shows the presence,
not the absence of bugs”
- Dijkstra

So, why test?

When working with dates, it takes a while
before the Boundary Values occure.

Isolate for productivity

• Test isolated units of code, assuring they are working
• No need to bother about it later
• No need to ﬁnd all edge cases in the user interface:
F5 syndrom

Isolate your tests

• Don’t test code that is tested elsewhere
• Only make sure it is used well in the code you’re testing
• The solution: mocks and stubs

Mock objects are simulated objects that mimic
the behavior of real objects in controlled ways

A stub is a piece of code used to stand in
for some other programming functionality

Very hard
Method A Method B
work

Method B Very hard
work

Method A

Method B Very hard
work

Method A Mock

Method B Very hard
work

Method A Stub

Mock

Method B Very hard
work

Method A

Mock Stub

How to isolate?
def create_invoice(contact)
invoice = Invoice.new
invoice.contact_id = contact.id
invoice.details_attributes =
[{ :description => "RER09", :price => 79 }]
invoice.save
end

class Invoice < ActiveResource::Base
self.site = "https://account.moneybird.com"
end

How to isolate?
def create_invoice(contact)
invoice = Invoice.new
invoice.contact_id = contact.id
invoice.details_attributes =
[{ :description => "RER09", :price => 79 }]
invoice.save
end

class Invoice < ActiveResource::Base
self.site = "https://account.moneybird.com"
end
ActiveResource is tested elsewhere +
very slow to test

describe "MoneyBird API" do
it "should create the invoice" do

create_invoice(contact_mock).should be_true
end
end


contact_mock = mock(:contact)
contact_mock.should_receive(:id).and_return(3)

end
end


Invoice.should_receive(:new).and_return(invoice_mock)


end
end

invoice_mock = mock(:invoice)
invoice_mock.stub!(:contact_id=)
invoice_mock.stub!(:details_attributes=)
invoice_mock.should_receive(:save).and_return(true)

Invoice.should_receive(:new).and_return(invoice_mock)


end
end

Isolation

Isolated A B

Not isolated A B

Isolation

Isolated A B

Not isolated A B
Double
=
Extra test work +
maintenance work!

What to test?
Everything!

But never too much!! Be critical

Downside of testing

• Every test gives overhead
• Testing the obvious takes time
• Ruby library, CRUD controllers

Downside of testing

• Every test gives overhead
• Testing the obvious takes time
• Ruby library, CRUD controllers
But what if suddenly:
BigDecimal("10.03").to_f != 10.03

We use (very) fat models

So we unit test them

RSpec

• All business logic in models
• Models tested with RSpec
• Basic data model in ﬁxtures

Fixtures?
• Models make use of the database
• Sometimes data in de database is needed
for the model to work
• Fixtures are easy to manage on the
ﬁlesystem (+ version control)
• Fixtures can be used for bootstrapping
application: rake db:ﬁxtures:load

first_contact:
company: bluetools
name: Edwins company
contact_name: Edwin Vlieg
address1: Street 82
zipcode: 7541 XA
city: Enschede
country: NL
send_method: mail
created_at: <%= 60.days.ago.to_s :db %>
contact_hash: 1
second_contact:
company: bluetools
name: BlueTools B.V.
address1: Postbus 123
zipcode: 7500EA
city: Enschede
country: NL
send_method: post
contact_hash: 2

first_contact:
company: bluetools
Unique identiﬁer for
name: Edwins company ‘row’ in database.
contact_name: Edwin Vlieg Don’t set the id column!!
address1: Street 82
zipcode: 7541 XA
city: Enschede
country: NL
send_method: mail
contact_hash: 1
second_contact:
company: bluetools
name: BlueTools B.V.
zipcode: 7500EA
city: Enschede
country: NL
send_method: post
contact_hash: 2

first_contact:
company: bluetools
address1: Street 82
zipcode: 7541 XA
city: Enschede
country: NL
send_method: mail
contact_hash: 1
second_contact:
company: bluetools
name: BlueTools B.V. Yes, you can use Ruby!
zipcode: 7500EA
city: Enschede
country: NL
send_method: post
contact_hash: 2

first_contact:
company: bluetools
address1: Street 82
zipcode: 7541 XA
city: Enschede
country: NL
send_method: mail
contact_hash: 1
second_contact:
company: bluetools
name: BlueTools B.V. Yes, you can use Ruby!
zipcode: 7500EA
city: Enschede
country: NL
send_method: post
contact_hash: 2 Reference to unique identiﬁer
in companies table

We don’t test controllers and views.

Because,

• Controllers are just plain CRUD actions
• Views just contain HTML
• And both are tested with integration
testing in Cucumber

The goal
• Test the full stack: models, views and
controllers
• Behaviour driven approach

Cucumber stories

• Each line is parsed and matched on a step
• Step contains actual execution of code
• 3 types of steps: Given, When and Then.

homepage.feature

When I follow "Signup"

webrat_steps.rb

When /^I follow "([^"]*)"$/ do |link|
click_link(link)
end

Reuse step deﬁnitions

In MoneyBird:

40 step deﬁnitions

695 steps executed

40 steps

• 21 Webrat steps (Cucumber default)
•4 Common steps (DB & Mailer)
• 15 Domain speciﬁc steps

Webrat

• Webrat gives you control over the user
interface (almost) like an end user has
• But doesn’t emulate a browser like
Selenium or Watir (= no JavaScript)

Web-what?
Web browser

Apache

Mongrel / Passenger Webrat

ActionController


1. Locate the link on the page
<a href="/signup">Signup</a>

<a href="/signup" title="Signup"><img src="..." /></a>

<a href="/signup" id="Signup" title="Click to signup"><img src="..."></a>


1. Locate the link on the page
<a href="/signup">Signup</a>

<a href="/signup" title="Signup"><img src="..." /></a>

<a href="/signup" id="Signup" title="Click to signup"><img src="..."></a>

2. ‘Click’ the link
Grab the ‘href’ attribute from the element and feed it to the
Rails application. HTML is replaced: next search of element
will be in new page.

Cucumber & Webrat
Cucumber comes with default Webrat steps to:
• Visit pages
• Click links
• Fill in forms
• Submit forms
• Assert the content of the page

Testability
Webrat doesn’t execute JavaScript, so write
unobtrusive JavaScript to keep it testable.

Testability

HTML
<a href="/popup.html" id="open">Open popup</a>

Link opens popup, even without JavaScript

Testability

HTML


JavaScript
$('open').click(...);

JavaScript adds extra behaviour to link

Testability

HTML


JavaScript
$('open').click(...);
Rails 3

JavaScript adds extra behaviour to link

Common steps
Database steps:
Given I've created an invoice with invoice id "2008-0100"

Then a contact with name "Test company" should exist

Mailer steps:
Then an e-mail with subject "Invoice 2008-0100 from
Bluetools" should have been sent

Full source: http://pastie.org/667777

Database steps

Given I've created an invoice with invoice id "2008-0100"

Should create a new invoice with invoice id
“2008-0100”, but what about the rest of the attributes?

FactoryGirl
• Makes it easy to create records in the
database
• Deﬁne default attributes for a record:
Factory.define :contact do |c|
c.company_id { |c| Company.find_by_domain($subdomain).id }
c.name "Test company"
c.contact_name "Edwin Vlieg"
c.address1 "Hengelosestraat 538"
c.zipcode "7500AG"
c.city "Enschede"
c.country "NLD"
c.email "test@moneybird.nl"
end

FactoryGirl
• Easy instantiation of records in database:
Factory(:contact, :name => "Foobar")

Factory name Override default
attributes

More information:
http://github.com/thoughtbot/factory_girl

Downside

What if we want to change “Signup”
to “Create account”?

Test breaks, but application is functionally correct.

Testing takes time,
so be critical about what to test

Don’t stare blindly at TDD or BDD

Creating mesmerizing products needs creativity,
this doesn’t always ﬁt into the ‘test-ﬁrst’ approach,

but know the ideas behind the approaches,
so you can use them when needed!

Creating a good test environment takes time:
it just doesn’t end with RSpec or Cucumber

Mocks, stubs, ﬁxtures and factories are your friends!

Write testable code

Keep the units small for easy unit testing

Keep the HTML clean for webrat

Advanced Testing Techniques with Ruby on Rails

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