XP Practice: TestFirst Development

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XP Practice Test-First Development

• Tuba Yavuz-Kahveci
• CEN 3031
• University of Florida

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Outline

• What is Test-First Development?
• User Stories
• Test Planning
• Implementing the Test
• JUnit Framework
• Implementing the Unit

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Test-First Development

• Traditional approach code first and then test
• may delay finding bugs
• Test-First design the test cases, implement the
  test, and finally do the coding
• Code enough to make the tests run successfully

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Test-First Development

• Advantages
• Refactor boldly and mercilessly
• Tests are rerun to see if the improved code still
  behaves the same way
• Supports collective code ownership
• Immediate feedback if a bug is introduced by
  another developer
• Quick and accurate integration
• Quick diagnosis of the source of any
  incompatibility

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Outline

• What is Test-First Development?
• User Stories
• Test Planning
• Implementing the Test
• JUnit Framework
• Implementing the Unit

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User Stories

• A user story is a short description of the system
  behavior for a particular feature
• Medium of communication between the customer and
  the developer
• Small stories
• frequent releases
• easier to make an estimate

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Example User Story
A customer can rent a movie for a period of time.
The customer gains some frequent renter points
depending on the type of the movie and the
rental period. The program prints the statement
for each rental and it should include the title
of the movies along with the individual prices,
the total amount owned, and the earned frequent
renter points.
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Possible Questions Answers

• Q What are the movie types?
• A regular, childrens, new release
• Q How is the price calculated?
• A

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Possible Questions Answers

• Q How is the frequent renter points calculated?
• A

• Q Is there any history keeping for the frequent
  renter points for each customer?
• A No.

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Possible Questions Answers

• How does a typical statement look like?

Statement for Customer_Name Movie_Title_1 Individu
al_Price_1 Individual_Freq_Rent_Points_1 Movie_Tit
le_1 Individual_Price_2 Individual_Freq_Rent_Point
s_2 Movie_Title_1 Individual_Price_N Individual_
Freq_Rent_Points_N Amount owed is
Total_price You earned Total_Freq_Rent_Points
frequent renter points
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Outline

• What is Test-First Development?
• User Stories
• Test Planning
• Implementing the Test
• JUnit Framework
• Implementing the Unit

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User Story ? Tasks

• Divide the implementation of the user story into
  tasks
• A high-level description of how the computation
  will be done

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Example Task
Implementing generation of the rental
statement Keep the title and the type of each
movie. Keep the list of rented movies for each
customer. For a given customer print the
statement Calculate the individual price and
the individual frequent renter points for each
rented movie, the total price and the frequent
renter points earned and print them as the
statement.
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Test Cases for the Task

• We dont have the code that implements the task
  yet!
• Black-box testing
• Identify the inputs and the outputs and their
  domains, i.e., the possible values they can take

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Inputs and Outputs

• Customer Name
• A set of movie rentals
• Title of the movie
• Type of the movie
• Rental period
• Statement

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Input Domains

• Customer Name
• Valid Two non-empty strings (first and last
  names)
• Invalid Any of the two an empty string
• A set of movie rentals
• Valid non-empty set of movie rentals
• Invalid empty set of movie rentals

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Input Domains

• Movie rental
• Title of the movie
• Valid non-empty string
• Invalid empty string
• Type of the movie
• Valid regular, childrens, new release
• Invalid other than regular, childrens, new
  release
• Rental Period
• Valid one or more days
• Invalid zero or less days

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Choosing Test Data

• We cannot test our program with every possible
  value in the input domain!
• Need some good representative values
• Solution Partition the input domains into
  equivalence classes based on the specification
• Input values that produce similar output should
  be in the same equivalence class

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Movie Rentalsr regular, c childrens, n new
release

• One rental r, c, n
• Two rentals r, c, n ? r, c, n
• All the same or all different
• Three rentals r, c, n ? r, c, n ? r, c, n
• All the same, two of them the same, all different
  
• Four rentals
• r, c, n ? r, c, n ? r, c, n ? r, c, n
• All the same, three of them the same, two of them
  the same, all different
• More than four rentals

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Rental Period (d)

• Regular
• d2 price2
• dgt2 price2(d-2)1.5
• Frequent renter points 1
• Independent of d
• Valid 1, 2, 3, 4, 5,
• Singletons for boundary value, boundary value-1,
  boundary value1
• Invalid -1, -2, , 0

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Rental Period (d)

• Childrens
• d3 price1.5
• dgt3 price1.5(d-3)1.5
• Frequent renter points 1
• Independent of d
• Valid 1, 2, 3, 4, 5, 6,
• Singletons for boundary value, boundary value-1,
  boundary value1
• Invalid -1, -2, , 0

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Rental Period (d)

• New release
• price3d
• d1 Frequent renter points 1
• dgt1 Frequent renter points 2
• Valid 1, 2, 3, 4,
• Singletons for boundary value, boundary value-1,
  boundary value1
• Invalid -1, -2, , 0

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Outline

• What is Test-First Development?
• User Stories
• Test Planning
• Implementing the Test
• JUnit Framework
• Implementing the Unit

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Implementing Tests

• Manual testing
• Run the program with test data
• Compare the expected output with the actual
  output in a nonsystematic (manual) way
• Costly to repeat
• Automated testing
• Implement the comparison of the expected output
  with the actual output once
• Do the testing by running the testing code as
  many times as needed!

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JUnit

• An automated testing framework
• Specialized classes for creating and
  manipulating
• Test cases TestCase class
• For implementing a test case given an input
  check if the output is equivalent to what is
  expected?
• Test suites TestSuite class
• For implementing a test suite does the program
  runs correctly for a different set of test cases?
• Test success failure Assert class

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• public class IntegerArithmetic
• public int add(int op1, int op2)
• public int subtract(int op1, int op2)
• public int multiply(int op1, int op2)
• public int divide(int op1, int op2)
• public int minus(int op)

import junit.framework. public class
testIntegerArithmetic extends TestCase
private IntegerArithmetic _calculator
private int _op1 private int _op2
public testIntegerArithmetic(String s)
super(s) protected void setUp()
_calculator new IntegerArithmetic()
_op1 5 _op2 6 public void
testAdd() Assert.assertEquals(_op1_op2,
_calculator.add(_op1,_op2))
// continued
Class to be tested
Test Class
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• public class IntegerArithmetic
• public int add(int op1, int op2)
• public int subtract(int op1, int op2)
• public int multiply(int op1, int op2)
• public int divide(int op1, int op2)
• public int minus(int op)

// continued
public static void main(String
args) junit.textui.TestRunner.run(new
testIntegerArithmetic("testAdd"
)) junit.textui.TestRunner.run(
testIntegerArithmetic.class)
junit.textui.TestRunner.run(suite())
public static Test suite()
TestSuite suite new TestSuite()
suite.addTest(new testIntegerArithmet
ic("testAdd")) suite.addTest(new
testIntegerArithmetic("test for mult..")
public void runTest()
testMultiply() )
suite.addTest(new testIntegerArithmetic(
"testSubtract")) return suite

Class to be tested
Test Class
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java junit.swingui.TestRunner
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After running the tests
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After running the tests
After implementing the subtraction as if it was
addition
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More Information

• Readins in Agile Development Methods Extreme
  Programming (textbook)
• Chapter 34 Building Tests
• http//www.junit.org
• http//junit.sourceforge.net/doc/testinfected/test
  ing.htm
• http//junit.sourceforge.net/doc/cookbook/cookbook
  .htm

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Outline

• What is Test-First Development?
• User Stories
• Test Planning
• Implementing the Test
• JUnit Framework
• Implementing the Unit

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Task
Implementing generation of the rental
statement Keep the title and the type of each
movie. Keep the list of rented movies for each
customer. For a given customer print the
statement Calculate the individual price and
the individual frequent renter points for each
rented movie, the total price and the frequent
renter points earned and print them as the
statement.
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A Quick Design
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testCustomer class

• Will be implemented using JUnit framework
• Extends testCase class
• A method for each test case
• Will make calls to
• Constructors of Customer, Movie, and Rental
  classes
• new Customer(joe)
• new Rental(new Movie(Troy,1),3)
• addRental and statement methods of Customer class

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testCustomer class

• Assignment! Your first group project task
• Due January 28th
• http//www.cise.ufl.edu/class/cen3031sp05/project.
  html
• You will learn JUnit and get to know your group
  members