CS110- Lecture 11
Mar 21, 2005
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Agenda
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Questions on Project 2?
JUnit Testing
Practice Session
toString() method
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Testing
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Unit Testing: To test each unit, or
component, independently, before the
units are integrated into the whole
system.
Integration and system testing: To
integrate all the components of a
system and to test the system as a
whole.
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Unit Testing
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Unit testing is important because
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For the whole system to function properly,
each of its components, or units, must
function properly individually.
Units are much smaller than the whole
system, it is much easier to find the errors
in each unit individually.
Good unit testing will reduce the effort and
cost required for integration significantly.
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Unit Testing
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In OOP the unit for unit testing is often
a single class.
Old style of testing: Carry out tests in
main method.
New style of testing: Write separate test
classes for testing purposes only.
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JUnit Testing
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When dealing with large set of test
cases it is usually more convenient to
use a unit testing tool.
JUnit is a flexible, easy to use, and
open source unit testing tool for java
programs.
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Template of a typical JUnit test program
public class TestX extends TestCase
// X is the class
// to be tested
{
private X x = null;
protected void setUp() throws Exception {
x = new X();
setUp is called before every
}
testCase is executed
protected void tearDown() throws Exception {
x = null;
tearDown is called after every
}
testCase is executed
//All test methods are public/protected not private
public void testCase1() {
//test and compare results
Name of test methods
}
starts with test
public void testCase2() {
//test and compare results
}
}
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Test class for Die.java
public class TestDie extends TestCase
//Die is the class
//to be tested
{
private Die die = null;
protected void setUp() throws Exception {
die = new Die();
}
protected void tearDown() throws Exception {
die = null;
}
public void testGetFaceValue() {
//test and compare results
int expectedReturn = 1;
int actualReturn = die.getFaceValue();
assertEquals(expectedReturn,actualReturn);
}
}
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JUnit features
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JUnit features include:
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Assertions for testing expected results
Test fixtures (setUp and tearDown) for
sharing common test data.
Graphical and textual test runners
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Practice Session
Point
x : double
y : double
Class Name
Data
getX() : double
Methods
getY(): double
setX (double x1) : void
setY (double y1) : void
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Practice Session
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Write a Point class from the UML
diagram in the previous slide.
Write a test class TestPoint for Point
class.
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toString() method
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toString() method takes no arguments.
It is supposed to return all the data in
an object coded into a String.
Return type is always String.
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toString() method for Point Class
public String toString()
{
return (“X = ” + x + “, Y = ” + y);
}
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How toString() method is used
public class PointClient
{
//Execution always starts from main
public static void main(String[] args)
{
Point p = new Point(3,4);
System.out.println(p.toString());
p.setX(6);
System.out.println(p.toString());
}
}
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Output
X = 3, Y = 4
X = 6, Y = 4
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Special property of toString()
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If you do not include it in an invocation
of System.out.println, it is invoked
automatically.
For example the bold part of the main
method on slide 13 is equivalent to
Point p = new Point(3,4);
System.out.println(p);
p.setX(6);
System.out.println(p);
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toString() method
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It is always a good idea to define a
suitable toString method for the classes
with instance data.
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