1. Java IO and Testing made simple
Viera K. Proulx and Richard Rasala
College of Computer and Information Science
Northeastern University
Boston MA
3/5/2004
Java IO and Testing Made Simple

2. 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
Java IO and Testing Made Simple
3/5/2004

3. 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
Java IO and Testing Made Simple
3/5/2004

4. Java IO and Testing Made Simple
Test suite development
ad hoc
cumbersome
no organization
(or) overwhelming (JUnit)
unreadable
bad habits early
Java IO and Testing Made Simple
3/5/2004

5. 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...
Java IO and Testing Made Simple
3/5/2004

6. 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
Java IO and Testing Made Simple
3/5/2004

7. Java IO and Testing Made Simple
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
Java IO and Testing Made Simple
3/5/2004

8. Java IO and Testing Made Simple
3/5/2004
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
Java IO and Testing Made Simple
3/5/2004
Java IO and Testing Made Simple

9. Java IO and Testing Made Simple
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
Java IO and Testing Made Simple
3/5/2004

10. Java IO and Testing Made Simple
User interactions
or for GUI TextFieldView xTFV:
int x;
try{
x = xTFV.requestDouble( ); }
catch (CancelledException e) {
System.out.println(“Input ends”);
Java IO and Testing Made Simple
3/5/2004

11. Java IO and Testing Made Simple
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:”);
Java IO and Testing Made Simple
3/5/2004

12. Java IO and Testing Made Simple
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?:”)); }
Java IO and Testing Made Simple
3/5/2004

13. Java IO and Testing Made Simple
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)
Java IO and Testing Made Simple
3/5/2004

14. 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
Java IO and Testing Made Simple
3/5/2004

15. 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
Java IO and Testing Made Simple
3/5/2004

16. 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
Java IO and Testing Made Simple
3/5/2004

17. 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( ));
Java IO and Testing Made Simple
3/5/2004

18. 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)
Java IO and Testing Made Simple
3/5/2004

19. Java IO and Testing Made Simple
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
Java IO and Testing Made Simple
3/5/2004

20. Java IO and Testing Made Simple
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
Java IO and Testing Made Simple
3/5/2004

21. Java IO and Testing Made Simple
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);
Java IO and Testing Made Simple
3/5/2004

22. Java IO and Testing Made Simple
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
Java IO and Testing Made Simple
3/5/2004

23. Java IO and Testing Made Simple
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”));
Java IO and Testing Made Simple
3/5/2004

24. Java IO and Testing Made Simple
User interactions
Test suite development
Input of data sets
Good Habits Early
Student experience: uniformly positive
Java IO and Testing Made Simple
3/5/2004

25. Java IO and Testing Made Simple
New initiatives and a workshop:
Java IO and Testing Made Simple
3/5/2004