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Testing/Testing In Rails 1 . Alan and Saskia 2/8/2008. Outline. Testing In General Unit Testing and Test First! Integration Testing Functional Testing Fixture Mocking with Mocha. Testing In General (1) ‏. Formal Definition

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Testing/Testing In Rails 1

Alan and Saskia



  • Testing In General

  • Unit Testing and Test First!

  • Integration Testing

  • Functional Testing

  • Fixture

  • Mocking with Mocha

Testing In General (1)

  • Formal Definition

    • Testing is the process of finding differences between the expected behavior specified by system models and the observed behavior of the implemented system.

    • The goal is to design tests that exercise defects in the system and to reveal problems

Testing In General (2)

  • Alternative Definition

    • Testing has to demonstrate that faults are not present at all.

      • Almost impossible to show

      • May lead to the selection of test data that have a low probability of causing the program to fail

  • Even more alternative (Wilson Bilkovich)‏

    • Writing applications without tests makes you a bad person, incapable of love.

Unit Testing in Ruby

  • Unit Testing

    • Testing small units of codes (normally methods)‏

  • Test::Unit

    • Ruby’s built-in testing framework

    • xUnit family (Java’s Junit, .NET’s Nunit)‏

  • Concepts

    • Assertions: comparison of expected value and result of an expression

    • Failure: assertion failure

    • Error: exception or runtime error

    • Green vs red bar

Unit Testing in Ruby (2)

  • require 'roman'

  • require 'test/unit'

  • class TestRoman < Test::Unit::TestCase

    • def setup

    • end

    • def test_simple

      • assert_equal("i", Roman.new(1).to_s)‏

      • assert_equal("ix", Roman.new(9).to_s)‏

    • end

    • def teardown

    • end

  • end

<<Class inclusion

<<super class

<<code to be run before all test methods

<<naming convention


<<code to be run after all test methods

Assertions (1)

  • assert(boolean, [ message ] )‏

    • Fails if boolean is false or nil.

  • assert_nil(obj, [ message ] )‏

  • assert_not_nil(obj, [ message ] )‏

    • Expects obj to be (not) nil.

  • assert_equal(expected, actual, [ message ] )‏

  • assert_not_equal(expected, actual, [ message ] )‏

    • Expects obj to equal/not equal expected, using ==.

  • assert_in_delta(expected_float, actual_float, delta, [ message ] )‏

    • Expects that the actual floating-point value is within delta of the expected value.

Assertions (2)

  • assert_raise(Exception, . . . ) { block }

  • assert_nothing_raised(Exception, . . . ) { block }

    • Expects the block to (not) raise one of the listed exceptions.

  • assert_instance_of(klass, obj, [ message ] )‏

  • assert_kind_of(klass, obj, [ message ] )‏

    • Expects obj to be a kind/instance of klass.

  • assert_respond_to(obj,message, [ message ] )‏

    • Expects obj to respond to message (a symbol).

  • assert_match(regexp, string, [ message ] )‏

  • assert_no_match(regexp, string, [ message ] )‏

    • Expects string to (not) match regexp.

  • assert_same(expected, actual, [ message ] )‏

  • assert_not_same(expected, actual, [ message ] )‏

    • Expects expected.equal?(actual).

Assertions (3)

  • assert_operator(obj1, operator, obj2, [ message ] )‏

    • Expects the result of sending the message operator to obj1 with parameter obj2 to be true.

  • assert_throws(expected_symbol, [ message ] ) { block }

    • Expects the block to throw the given symbol.

  • assert_send(send_array, [ message ] )‏

    • Sends the message in send_array[1] to the receiver in send_array[0], passing the rest of send_array as arguments. Expects the return value to be true.

  • flunk(message="Flunked")‏

    • Always fail.

Test First!

  • What is it about?

    • Write the test cases first. Then write minimal codes to pass the tests

    • Write more tests. Write more minimal codes to pass the tests

    • Iterate the process till all functional requirements are satisfied 

Test First Guidelines

  • The name of the test should describe the requirement of the code

  • There should be at least one test for each requirement of the code. Each possible path through of the code is a different requirement

  • Only write the simplest possible code to get the test to pass, if you know this code to be incomplete, write another test that demonstrates what else the code needs to do

  • A test should be similar to sample code, in that it should be clear to someone unfamiliar with the code as to how the code is intended to be used

  • If a test seems too large, see if you can break it down into smaller tests

  • If you seem to be writing a lot of code for one little test, see if there are other related tests you could write first, that would not require as much code

  • More at http://www.xprogramming.com/xpmag/testFirstGuidelines.htm

Unit Testing in Rails

  • In rails, unit testing is geared towards testing of individual functions created in a model

  • For each model generated, a test file is automatically created in tests/unit directory

  • script/generate model product name:string description:string

  • exists app/models/

  • exists test/unit/

  • exists test/fixtures/

  • create app/models/product.rb

  • create test/unit/product_test.rb

  • ….

Testing/Testing In Rails 1 Saskia


  • Testing In General

  • Unit Testing and Test First!

  • Integration Testing

  • Functional Testing

  • Fixture

  • Mocking with Mocha

Integration Testing in RoR

  • Integration Testing

    • story-level, tests interactions & interfaces of various actions supported by the application, across all controllers

    • Find bugs with session management and routing, triggered by certain cruft accumulating in a user’s session

  • In 'test/integration':

    • Create test file with 'script/generate integration_test stories_test'

    • Class IntegrationTest inherits from Test::Unit

Integration Testing in RoR

  • Story set describes how the application ought to function

    • Interfaces: exchange of right data

    • Interaction: employment of right components

      • Example: signing up, getting account, multiple users

  • Testing time grows with number of integrated units

    • Bottom-Up: Integrate tested Units to subsystems as new components

Integration Testing in RoR

File'stories_test.rb' in 'test/integration':

  • require "#{File.dirname(__FILE__)}/../test_helper"

  • class StoriesTest < ActionController::IntegrationTest

    • fixtures :users, :accounts

    • def test_stories

    • get "/signup"

    • assert_response :success

    • assert_template "signup/index"

    • post "/signup", :name => "Bob", :user_name => "bob",

    • :password => "secret"

    • assert_response :redirect

    • follow_redirect!

    • assert_response :success

    • assert_template "account/index"

    • end

<<class inclusion

<<Integration Test Class

<<naming convention


Integration Testing in Ruby (2)

Run by: rake test_integration or ruby stories_test.rb




Finished in 0.01 seconds.

1) Failure:

where/which test

what went wrong

2) Error:

where/which test


what went wrong

5 tests, 9 assertions, 1 failure, 1 error.

<<Each spot represents a test, sorted alphabetically,

3 values: . means successful test (pass)‏

F means failed test

E means an error occurred

<<Listing of failures & errors:

Details on where and what

Moves on with first wrong assertion.

Functional Testing in Ruby

  • Functional Testing

    • single controllers and interactions between the models it employs

  • In directory 'test/function':

    • 'functional_controller_test.rb'stubs for each'script/generate controller'

Functional Testing in RoR

require File.dirname(__FILE__) + '/../test_helper'

require 'home_controller'

class HomeControllerTest < Test::Unit::TestCase

def setup

@controller = HomeController.new

@request = ActionController::TestRequest.new

@response = ActionController::TestResponse.new


def test_index

get :index

assert_response :success



<< grab HomeController for testing

<< setup of 3 typical funtional Test objects:

* controller to be tested

* TestRequest to

simulate web request

* TestResponse to provide

information about test request

<< test of main index page

<< get method simulates request on action called index .

<< assertion assures that request successful

5 request types supported as methods in Rails:

get, post, put, head, delete

Fixtures in RoR

  • Fixtures: automatically created sample data

    • To fill testing database with predefined data before tests run

    • database independent

    • Require explicit loading with fixtures method within test class

  • In directory 'test/fixtures':

    • fixture stubs for each 'script/generate model'

  • Formats

    • YAML: good readability, file extension '.yml'

    • CSV: comma-separated value file format, '.csv', easy reuse of existing data in spreadsheet/database (save/export as CSV)‏


File 'persons.yml' of YAML-Fixtures in 'text/fixtures':

# This is a YAML comment!


id: 1

name: David Dwarf

birthday: 0010-01-01

profession: slingshoter


id: 2

name: Goliath Giant

birthday: 0000-02-22

profession: terrorizer

<< name1

<< list of values

<< fixture-records separated by blank line

<< name2

each fixture:

* 'fixture-name'

* list of colon-separated key/value pairs


File 'users.csv' of CSV-Fixtures in 'text/fixtures':

<< header: first line, comma- separated list of fields

id, username, password, intelligent, comments

1, dhow, imstupid, false, I laugh ""Ha! Ho! Hu!""

2, admin, ihatedhows, true, What a mess!

3, nobody, ilovetomock, true, "Nobody mocks you"

4, nulpe,, false,

<< list of value-records,

one record per line


* each cell stripped of outward facing spaces

* comma as data: cell must be encased in quotes

* quote as data: must escape it with 2nd quote

* no blank lines

* nulls achived by placing comma

CSV fixture names automatically generated: “model-name”-”counter”




Fixtures in Action

# allow this test to hook into the Rails framework

require File.dirname(__FILE__) + '/../test_helper'

# need to include a User for testing

require 'user'

class UserTest < Test::Unit::TestCase

fixtures :users

def test_count_fixtures

assert_equal 5, User.count



<< fixture-load method:

* destroys any data in users table

* loads fixture data into users table

* dumps the data into a variable for direct access

automatic load of the fixtures at the start of each test method

Hashes with Fixtures

Fixtures are basically Hash objects:

- direct access via generated local variable of the test case

Fixtures can get form of the original class:

- access to methods only available to that class


fixtures :users, :person

def test_user




def test_person

david = users(:david).find

email( david.girlfriend.email, david.illegitimate_children )‏



<< load multiple fixtures separated by commas

<< returns Hash for fixture named david

<< returns id-property of david

<< using find method to grab "real" david as Person

<<now: access to

methods only available to a Person class

Mocking with Mocha

  • Problem with Fixtures

    • Fixtures makes testing slow (engage the actual DB)‏

    • Fixtures allow invalid data

    • Maintainability Challenges

    • Fixtures are brittle

  • That’s why we need Mocha (http://mocha.rubyforge.org/)

    • It provides stubs and mocks to simulate data, especially data in the database

Installing Mocha

  • sudo gem install mocha

  • In rails, include in test/test_helper.rb

  • require ‘mocha’

Do Not Mock My Stub

  • Stubbing (State Verification)‏

    • Stubbing a method is all about replacing the method with code that returns a specified result (or perhaps raises a specified exception).

  • Mocking (Behavior Verification)‏

    • Mocking a method is all about asserting that a method has been called (perhaps with particular parameters).

  • it’s difficult (or impossible?) to do mocking without stubbing - you need to return from the mocked method, so that the code under test can complete execution

  • http://www.martinfowler.com/articles/mocksArentStubs.html

Stubbing example (stub)

require 'test/unit'

require 'rubygems'

require 'mocha'

class TestProduct < Test::Unit::TestCase

def test_product

product = stub('ipod_product', :manufacturer => 'ipod', :price => 100)‏

assert_equal 'ipod', product.manufacturer

assert_equal 100, product.price



More stubbing example (stubs)

class View

attr :document

def initialize(document)‏

@document = document


def print()‏

if document.print

puts "Excellent!"



puts "Bummer."





require 'test/unit'

require 'rubygems'

require 'mocha'

class ViewTest < Test::Unit::TestCase

def test_should_return_false_for_failed_print

document = stub("my document")‏


ui = View.new(document)‏

assert ui.print



Mocking example (expects)

class Enterprise

def initialize(dilithium)‏

@dilithium = dilithium


def go(warp_factor)‏


{ @dilithium.nuke(:anti_matter) }



require 'test/unit'

require 'rubygems'

require 'mocha'

class EnterpriseTest < Test::Unit::TestCase

def test_should_boldly_go

dilithium = mock()‏


enterprise = Enterprise.new(dilithium)‏




Expects More Mocking

  • Methods in expects:

    • at_least, at_least_once, at_most, at_most_once, in_sequence, multiple_yields, never, once, raises, returns, then, times, when, with, yields