CSC/ECE 517 Fall 2010/ch1 1f TU

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Unit-testing frameworks for Ruby

Unit Testing

A unit is the smallest building block of a software. Such a unit can be: a class, a method, an interface etc. Unit testing is the process of validating such units of code.

Benefits

Some of the benefits are:

  • Proof of your code.
  • Better design - Thinking about the tests can help us to create small design elements, thereby improving the modularity and reusability of units.
  • Safety net on bugs - Unit tests will confirm that while refactoring no additional errors were introduced.
  • Relative cost - It helps to detect and remove defects in a more cost effective manner compared to the other stages of testing.
  • Individual tests - Enables us to test parts of a source code in isolation.
  • Less compile-build-debug cycles - Makes debugging more efficient by searching for bugs in the probable code areas.
  • Documentation - Designers can look at the unit test for a particular method and learn about its functionality.

Unit-testing frameworks

Unit Test Framework is a software tool to support writing and running unit test.

The above diagram shows the relationships of unit tests to production code. Application is built from objects linked together. The unit test uses this application's objects but exists inside the unit test framework.

List of most popular unit testing frameworks for Ruby

  • Test::Unit
  • RSpec
  • Shoulda
  • Cucumber

Simple application code in Ruby

Let us write a Calculator class in a file called calculator.rb. It has four methods addition, subtraction, multiplication and division. Later in the chapter we shall write tests in each of the above frameworks respectively. 

class Calculator 
 
 attr_writer :number1 
 attr_writer :number2
 
 def initialize(number1,number2)
   @number1 = number1
   @number2 = number2
 end
#-----------Addition of two numbers----------------#
 def addition
   result = @number1 + @number2
   return result
 end
#----------Subtraction of two numbers--------------#
  def subtraction
    result= @number1 - @number2
    return result
  end
#----------Multiplication of two numbers------------#
  def multiplication
    result= @number1 * @number2
    return result
  end
#-----------Division of two numbers-------------------#
 def division
   result = @number1 / @number2
   return result
 end
end

Test::Unit

Features of Test::Unit

Assertions
An assertion statement specifies a condition that you expect to hold true at some particular point in your program. If that condition does not hold true, the assertion fails. An error is propagated with pertinent information so that you can go back and make your assertion succeed.
Test Fixture
A test fixture is all the things we need to have in place in order to run a test and expect a particular outcome. Sometimes it is also knows as the test context. A Test Suite is a collection of test cases. A test fixture is useful if you have two or more tests for a common set of objects. Using a test fixture avoids duplicating the code necessary to initialize (and cleanup) the common objects.
Test Method
A test method is a definitive procedure that produces a test result.
Test Runners
To run the test class and view any failures that occur during the run we need a Test Runner. Examples -Test::Unit::UI::Console::TestRunner, Test::Unit::UI::GTK::TestRunner, etc.
Test Suite
A collection of tests which can be run.

Installing Test::Unit

Ruby 1.8 comes preinstalled with Test::Unit framework.

Usage

The general idea behind unit testing is that you write a test method that makes certain assertions about your code, working against a test fixture (a common set of data). The results of a run are gathered in a test result and displayed to the user through some UI. To write a test, follow these steps:

  • require ‘test/unit’ in your test script.
  • Create a class that subclasses Test::Unit::TestCase.
  • Add a method that begins with "test" to your class.
  • Make assertions in your test method.
  • Optionally define setup and/or teardown to set up and/or tear down your common test fixture.
  • Run your test as Test::Unit Test.
Example of a test class
 require "calculator"
 require "test/unit"

 class TC_Calculator < Test::Unit::TestCase
  
  
  def test_addition
    assert_equal(8,Calculator.new(3,4).addition)
   
  end
 
  def test_subtraction
   assert_same(1,Calculator.new(4,3).subtraction)
  end
 
  def test_multiplication
   assert_not_same(12,Calculator.new(3,4).multiplication)
  end
 
  def test_division
     assert_not_equal(5,Calculator.new(8,2).division)
  end
 end

If we run this test, here is how it'll look like -

Shoulda

Features of Shoulda

  • It is a library that allows us to write better and more understandable tests for your Ruby application.
  • It overdrives Test::Unit framework.
  • It allows to run test with the help of Test::Unit Configurations.
  • It provide us Helpers like context and should in the form of text blocks.We can write tests name in simple sentences rather following any naming conventions.
  • With the help of Macros we can generate hundred lines of codes.It also ensures that our application is confirmed to the best practice.

Installing Shoulda

If your Environment path is set to " ...\Ruby\bin" then open command prompt and run gem install shoulda.

Usage

So here is our class "TC_Calculator_Shoulda" which inherits "Test::Unit::TestCase".

  • Add require"rubygems" and require "shoulda" to the script.
  • Create a context
  • Define method starting with should and give an description to the method.
  • Create assertions to test the application objects.


 require "rubygems"
 require "calculator"
 require "test/unit"
 require "shoulda"

 class TC_Calculator_Shoulda < Test::Unit::TestCase

  context "Calculate" do

   should "addition of two numbers " do
     assert_equal 8,Calculator.new(3,4).addition 
   end

   should "subtraction of two numbers " do
    assert_equal 1,Calculator.new(4,3).subtraction
   end

   should "multiplication of two numbers" do
    assert_equal 12,Calculator.new(3,4).multiplication
   end

   should "division of two numbers" do
    assert_equal 4,Calculator.new(12,3).division
   end

  end

 end

When we run above test as "Ruby Application" we will get the output as follows. 

Loaded suite tc__calculator__shoulda
Started
F...
Finished in 0.064 seconds.
 1) Failure:
    test: Calculate should addition of two numbers . (TC_Calculator_Shoulda)
    <8> expected but was
    <7>.
4 tests, 4 assertions, 1 failures, 0 errors

RSpec

Features of RSpec
  • Establishing behavior - Allows developers to write system requirements in a Ruby format first and then write Ruby code for the particular features of those requirements.
  • BDD mandates that developers write tests for each step of the process, which leads to cleaner code. The BDD process begins with the development team creating a scenario, for which they describe each feature. The initial scenario inevitably fails. The team subsequently defines each step (iterative test) and writes the application code for each feature. They also refactor the code when the scenario passes each step.

Installing RSpec

If your Environment path is set to " ...\Ruby\bin" then open command prompt and run gem install rspec.

Usage

Initial spec

You start by describing what your application, method or class should behave like. Let us create our first specification file: 

require "calculator"

describe "TheCalculator's", "basic calculating" do

  it "should add two numbers correctly" do

  it "should subtract two numbers correctly" do

  it "should multiply two numbers correctly" do

  it "should divide two numbers correctly" do

  #...

end

What do we have here? First, at line 2 we defined a context for our test, using RSpec's describe block. Furthermore we have four behaviors/expectations (it "should ..." -blocks), defining what we expect our system to behave like.

We can run this specification using the spec command:

$ spec unit_test.rb

produces: 

****

Pending:

TheCalculator's basic calculating should add two numbers correctly (Not Yet Impl
emented)
./21file.rb:5

TheCalculator's basic calculating should subtract two numbers correctly (Not Yet
 Implemented)
./21file.rb:7

TheCalculator's basic calculating should multiply two numbers correctly (Not Yet
 Implemented)
./21file.rb:9

TheCalculator's basic calculating should divide two numbers correctly (Not Yet I
mplemented)
./21file.rb:11

Finished in 0.021001 seconds

4 examples, 0 failures, 4 pending
Establishing behavior

Isn't it cool? Executing the tests echoes our expectations back at us, telling us that each has yet to be implemented. This is forcing/establishing behavior. We know that all calculator's must perform the above functions. We don't know how we're going to design this yet, but the tests will derive our design.

Writing the application code

At the very end, you write the application code, and fire up the tests to check, if it behaves the way you wanted while writing the tests… but we're getting ahead of ourself.

Developing the code

Let's go a step further and associate code blocks with our expectations. 

require "calculator"

 describe "TheCalculator's", "basic calculating" do
  before(:each) do
    @cal = Calculator.new(6,2)
  end

  it "should add two numbers correctly" do
    @cal.addition.should == 8
  end

  it "should subtract two numbers correctly" do
    @cal.subtraction.should == 4
  end

  it "should multiply two numbers correctly" do
    @cal.multiplication.should == 11
  end

  it "should divide two numbers correctly" do
    @cal.division.should == 3
  end

end

Note that creating a Calculator object for each of our expectations will create duplication in the specification. This can be fixed using a before stanza in the specification. It allows us to run code before expectations are executed.

Let us run it:

produces: 

Spec::Expectations::ExpectationNotMetError:
expected: 11,
     got: 12 (using ==)
./unit_test.rb:17

Uh-oh! The third expectation did not meet. See how the error message uses the fact that the expectation knows both the expected and actual values.

In eclipse RSpec will generate a nice description text for you when an expectation is not met.



RSpec is about Behavior Driven Development. It's about encouraging conversation about testing and looking at it in different ways. It's about illuminating the design, specification, collaboration and documentation aspects of tests, and thinking of them as executable examples of behavior.

Cucumber

Features of Cucumber

  • Its a Behavior Driven Development(BDD) tool for Ruby.
  • It focuses on story styling plain English Text.
  • It follows GWT(Given,When,Then) pattern

Installing Cucumber

If your Environment path is set to " ...\Ruby\bin" then open command prompt and run gem install cucumber.

Usage

Let us first create a feature file to describe about our requirements 

Feature: Addition
  In order perform addition of two numbers
  As a user
  I want the sum of two numbers

  
Scenario: Add two numbers
   Given I have entered <input1>
   And   I have entered <input2>
   When  I give add
   Then  The result should be <output>

Then we will create a ruby file to give a code implementation 

require 'calculator'

Before do
 @input1=3
 @input2=4
end

Given /^I have entered <input(\d+)>$/ do |arg1|
   @calc = Calculator.new(@input1,@input2)
end

When /^I give add$/ do
  @result = @calc.addition
end

Then /^The result should be <output>$/ do
 puts @result
end

Now if we run the feature file we will get the following 

Feature: Addition
  In order perform addition of two numbers
  As a user
  I want the sum of two numbers

  Scenario: Add two numbers            # calculator.feature:7
    Given I have entered <input1>      # addition.rb:8
    And I have entered <input2>        # addition.rb:8
    When I give add                    # addition.rb:12
7
    Then The result should be <output> # addition.rb:16

1 scenario (1 passed)
4 steps (4 passed)
0m0.010s

Comparison of Test::Unit, Shoulda, RSpec


Test::Unit Shoulda RSpec
Test::Unit is a testing framework provided by Ruby.It is based on Test Driven Development. Shoulda is an extension to Test::Unit.
It is basically Test::Unit with more capabilities and simpler readable syntax. 		RSpec is a Behavior Driven Development framework provided by Ruby.
Test::Unit provides assertions,test methods like setup,teardown,test fixtures,test runners and test suites Shoulda provide macros,helpers like context and should,matchers RSpec provides a Domain Specific Language to express the behavior of code.Basically RSpec is TDD embraced with documentation.
Test::Unit does not allow nested setup and nested teardown though multiple setup methods and teardown methods are provided in Test::Unit 2.0 Shoulda allows nested contexts which helps to create different environment for different set of tests. RSpec allows nested describe structure.


Conclusion


I like RSpec best since I find the output to be most readable. I love the pending keyword, which allows me to set up the tests to be written later on. I find it helps focus on exactly one test and one failure. Shoulda would be our second choice because the tests are just as readable as RSpec, even if the output takes some learning to read.

Comparison of run times

The following are the run times for these three frameworks testing the same calculator class with 4 succesful tests -

RSpec

Finished in 0.023002 seconds
4 examples, 0 failures

Shoulda

Finished in 0.002 seconds.
4 tests, 4 assertions, 0 failures, 0 errors

Test::unit

Finished in 0.001 seconds.
4 tests, 4 assertions, 0 failures, 0 errors

External Links

RSpec
RSpec Documentation

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