Java IO and Testing made simple

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Java IOand Testingmade simple

• Viera K. Proulx and Richard Rasala
• College of Computer and Information Science
• Northeastern University
• Boston MA
• vkp_at_ccs.neu.edu
• rasala_at_ccs.neu.edu

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Java IO and Testing Made Simple

• Teaching with Java many problems
• We address three of them
• User interactions
• Test suite development
• Small vs. large data sets for algorithms

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Java IO and Testing Made Simple

• Reading user input
• from console or from GUI
• complicated
• buggy
• convoluted
• repetitious
• illustrates bad programming in the best way

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Java IO and Testing Made Simple

• Test suite development
• ad hoc
• cumbersome
• no organization
• (or) overwhelming (JUnit)
• unreadable
• bad habits early

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Java IO and Testing Made Simple

• Small vs. large data sets for algorithms
• internal data vs. external data
• treated differently
• programs are re-written for file input
• omitted from most text books
• no understanding of the need for stress tests
• ... bad habits early...

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Java IO and Testing Made Simple

• Solutions
• toolkit support for type-safe robust input
• from console and GUI
• with well designed user interface
• framework to support separate test class
• to act as a client class encapsulates the test
  suite
• leverage abstractions of traversals via iterators
• to supply data for algorithm testing

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User interactions

• Reading user input
• from console or from GUI
• requires parsing, conversion, error reporting
• JPT toolkit
• one method does it all
• uniform for console and GUI

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User interactions

• prompt displayed in the console
• input string is parsed
• expressions are evaluated and converted
• errors reported awaiting user correction
• value of the correct type delivered
• option to cancel input is available

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User interactions

• In student code
• int x console.in.demandInt(Number)
• In console program output user input system
  error
• Number 34x
• Expected end of expression.
• 34x
• Number 34

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User interactions

• or for GUI TextFieldView xTFV
• int x
• try
• x xTFV.requestDouble( )
• catch (CancelledException e)
• System.out.println(Input ends)

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User interactions

• Input of compound data entire object
• in real life Serializable (unreadable)
• For student programs we want to deliver
• an instantiated object in one method call
• Person p testClass.demandPerson(P)

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User interactions

• Person p testClass.demandPerson(P)
• Person demandPerson(String prompt)
• console.out.println(prompt)
• return new Person(
• console.in.demandString(Name),
• console.in.demandInt(Age),
• console.in.demandBoolean(Married?))

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User interactions

• for GUIs
• we can build a custom GUI that delivers
• compete Person instance
• PersonView pView new PersonView(...)
• Person p pView.demandPerson( )
• (JPT makes this easy - we really mean it)

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Test Suite Development

• interface Comparable...
• class Person...
• class Address...
• abstract class Job...
• class Clerk extends Job...

• Test goals
• Create objects in classes
• Person, Address, Clerk
• Test
• methods in all classes
• Tests illustrate
• the use of objects and classes
• in real programs

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Test Suite Development

• Test class requirements
• needs to instantiate objects in target classes
• needs to test methods in target classes
• they should be grouped by the target class
• there should be a comment on the purpose
• needs an option to run only some tests
• access to user input and output graphics, GUI

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Test Suite Development

• Java Power Framework
• TestClass constructor invokes an application
  that provides
• access to the JPT console and its methods
• access to a buffered graphics window
• a button for each proper method in TestClass
• proper method void, no arguments

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Test Suite Development

• public class TestSuite extends JPFalt
• public static void main(String args)
• new TestSuite( )
• Person p new Person(Roger, 34, true)
• void testIsOld( )
• testHeader(isOld)
• expected(false)
• actual(p.isOld( ))

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Test Suite Development

• Sample test results in the console
• Testing method isOld
• Expected false
• Actual false
• expected(arg) and actual(arg) methods
• are implemented for all primitive types
• and for Object with toString() method
• (Students implement toString() for all classes)

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Input of Data Sets

• Sorting algorithms, Hash tables, Graphs, etc.
• sort a List of Person-s by age
• sort an Array of Person-s by name
• List, Array a Collection
• by age, by name a Comparator
• what data to sort? - typically students change
  the code for different sources

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Input of Data Sets

• Goal
• sort any data that implements Collection
• use the given Comparator
• use the given data source
• Solution
• provide an iterator for the data source
• copy the data into your kind of Collection

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Input of Data Sets

• Iterator for the data source (interface IRange)
• modified to fit Java for-loop
• delivers current object without advancing
• For each data set used in algorithms
• provide method in algorithm setup class
• DataSet initialize(IRange it)

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Input of Data Sets

• Implementing the iterator
• for input from the console
• we already can input complete objects
• for input from GUI same idea
• for input from existing test data
• for input from a file
• helper extracts object data from a line

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Input of Data Sets

• Examples
• DataSet ds1 algSetup.initialize(
• new MyDataRange(someData))
• DataSet ds2 algSetup.initialize(
• new MyConsoleRange())
• DataSet ds3 algSetup.initialize(
• new MyFileRange(myFile.txt))

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Java IO and Testing Made Simple

• User interactions
• Test suite development
• Input of data sets
• Good Habits Early
• Student experience uniformly positive

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Java IO and Testing Made Simple

• http//www.ccs.neu.edu/jpt
• New initiatives and a workshop
• http//www.ccs.neu.edu/home/vkp