	CS 535 Object-Oriented Programming & Design Fall Semester, 2000 Testing
	Previous Lecture Notes Index Next © 2000, All Rights Reserved, SDSU & Roger Whitney San Diego State University -- This page last updated 30-Aug-00

Contents of Doc 3, Testing

References
JUnit Cookbook Local copy at: http://www.eli.sdsu.edu/java-SDSU/junit/cookbook/cookbook.htm

JUnit Test Infected: Programmers Love Writing Tests Local copy at: http://www.eli.sdsu.edu/java-SDSU/junit/testinfected/testing.htm

JUnit on-line documentation Local copy at: http://www.eli.sdsu.edu/java-SDSU/docs/

Originals of the above can be found at: http://www.junit.org/


Doc 3, Testing Slide # 2

Testing

Johnson's Law

If it is not tested it does not work

Types of tests

Unit Tests

Tests individual code segments

Functional Tests

Test functionality of an application


Doc 3, Testing Slide # 3

Why Unit Testing

If it is not tested it does not work

The more time between coding and testing

More effort is needed to write tests More effort is needed to find bugs Fewer bugs are found Time is wasted working with buggy code Development time increases Quality decreases

Without unit tests

Code integration is a nightmare Changing code is a nightmare


Doc 3, Testing Slide # 4

When to Write Unit Tests

First write the tests

Then write the code to be tested

Writing tests first saves time

Makes you clear of the interface & functionality of the code

Removes temptation to skip tests


Doc 3, Testing Slide # 5

JUnit

Framework for unit testing Java code

Available at: http://www.junit.org/

Already installed in JDK 1.2 on rohan and moria

Ports of JUnit are available in

C++	Delphi	Eiffel
Forte 4GL	Objective-C	Perl
PowerBuilder	Python	Ruby
Smalltalk	Visual Basic

See http://www.xprogramming.com/software.htm to download ports of JUnit


Doc 3, Testing Slide # 6

Using JUnit

Example
Goal: Implement a Stack containing integers.

Tests:

Subclass junit.framework.TestCase
Methods starting with 'test" are run by TestRunner

First tests for the constructors:

package example;
import junit.framework.TestCase;
public class  StackTest extends TestCase {
   //required constructor
   public StackTest(String name) {
      super(name);
   }
   
   public void testDefaultConstructor() {
      Stack test = new Stack();
      assert( test.isEmpty() );
   }
      
   public void testSizeConstructor() {
      Stack test = new Stack(5);
      assert( test.isEmpty() );
   }
}


Doc 3, Testing Slide # 7

First part of the Stack

package example;
public class Stack  {
   int[] elements;
   int topElement = -1;
   
   public Stack() {
    this(10); 
   }
   public Stack(int size) { 
      elements = new int[size]; 
   }
   
   public boolean isEmpty() {
      return topElement == -1;
   }
}
Doc 3, Testing Slide # 8

Running JUnit
JUnit has three interfaces

Text (junit.textui.*)

AWT (junit.ui.*)

Swing (junit.swingui.*)

Shows list of previously run test classes

JUnit has two class loaders

Normal java class loader (TestRunner)

junit.util.TestCaseClassLoader (LoadingTestRunner)

Reloads classes without having to restart program


Doc 3, Testing Slide # 9

Starting TestRunner
Make sure your classpath includes the code to tested

On Rohan use:

java junit.ui.LoadingTestRunner
You get a window like:

Doc 3, Testing Slide # 10

Enter the full name of the test class

Click on the Run button


If there are errors/failures select one and click on Show
You will see a stack trace of the error
With LoadingTestRunner you can recompile the Stack & StackTest classes without exiting LoadingTestRunner
Doc 3, Testing Slide # 11

Testing the Tests
If can be useful to modify the code to break the tests

package example;
public class Stack  {
   int[] elements;
   int topElement = -1;
   
   etc.
   
   public boolean isEmpty() {
      return topElement == 1;
   }
}

One company had an automatic build and test cycle that ran at night. The daily build was created and all the tests were run at night. The test results were available first thing in the morning. One night the build process crashed, so the daily build was not made. Hence there was no code to test. Still 70% of the tests passed. If they had tested their tests, they would have discovered immediately that their tests were broken.


Doc 3, Testing Slide # 12

Test Fixtures

Before each test setUp() is run

After each test tearDown() is run

package example;
import junit.framework.TestCase;
public class  StackTest extends TestCase {
   Stack test;
   
   public StackTest(String name) {
      super(name);
   }
   
   public void setUp() {
      test = new Stack(5);
      for (int k = 1; k <=5;k++)
         test.push( k);   
   }
   public void testPushPop() {
      for (int k = 5; k >= 1; k--)
         assert( "Popping element " + k,  test.pop() == k);
   }
}
Doc 3, Testing Slide # 13

Suites – Multiple Test Classes

Multiple test classes can be run at the same time

Running AllTests in TestRunner runs the test in

StackTest
QueueTest

package example;
import junit.framework.TestSuite;
public class AllTests 
{
   static public TestSuite suite()
      {
         TestSuite suite= new TestSuite();
      try
         {
          suite.addTest(new TestSuite(StackTest.class));
          suite.addTest(new TestSuite(QueueTest.class));
          }
       catch (Exception e)
          {
          }
          return suite;
      }
}


Doc 3, Testing Slide # 14

Using Main

We can use main to run the test via textui.TestRunner

The command:

   java example.AllTests

will run all the tests in StackTest & QueueTest

package example;
import junit.framework.TestSuite;
import junit.textui.TestRunner;
public class AllTests 
   {
   static public void main(String[] args) 
      {
      TestRunner.main(args);
      }
      
   static public TestSuite suite()
      {
      same as last page
      }
   }
Doc 3, Testing Slide # 15

Just For Completeness

The QueueTest and Queue classes exist but don't do much

package example;
import junit.framework.TestCase;
public class QueueTest extends TestCase
   {
   public QueueTest( String name)
      {
      super(name);
      }
   public void testConstructor()
      {
      Queue test = new Queue();
      assert( test.isEmpty());
      }
   }

package example;
import java.util.Vector;
public class  Queue
   {
   Vector elements = new Vector();
   public boolean isEmpty()
      {
      return elements.isEmpty();
      }
   }
Doc 3, Testing Slide # 16

Why not just use print statements?
Using print statements does not scale

package example;
public class StackTest {
   public static void main( String[] args ) {
      Stack test = new Stack();
      System.out.println( "Expect: true Result: " + 
         test.isEmpty());
      test = new Stack(5);
      System.out.println( "Expect: true Result: " + 
         test.isEmpty();
   }
}


Doc 3, Testing Slide # 17

What to Test

Everything that could possibly break

Test values

Inside valid range
Outside valid range
On the boundary between valid/invalid

GUIs are very hard to test

Keep GUI layer very thin
Unit test program behind the GUI, not the GUI


Doc 3, Testing Slide # 18

The Complete JUnit Example

Stack

package example;
public class Stack  {
   int[] elements;
   int topElement = -1;
   
   public Stack()    { this(10); }
   public Stack(int size) { elements = new int[size]; }
   
   public boolean isEmpty() {
      return topElement == -1;
   }
   
   public boolean isFull() {
      return topElement == elements.length-1;
      }
   public void push( int element) {
      topElement++;
      elements[topElement] = element;
      }
   public int pop() {
      return elements[topElement--];
      }
   }
Doc 3, Testing Slide # 19

StackTest

package example;
import junit.framework.TestCase;
public class  StackTest extends TestCase {
   public StackTest(String name) {
      super(name);
   }
   
   public void testDefaultConstructor() {
      Stack test = new Stack();
      assert( test.isEmpty() );
   }
      
   public void testSizeConstructor() {
      Stack test = new Stack(5);
      assert( test.isEmpty() );
   }
   public void testUnderflow() {
      Stack test = new Stack(512345);
      test.push( 1);
      test.pop();
      try {
         test.pop();
         fail( "Pop on empty stack passed");
      }
      catch (Exception overflow) {
      }
   }


Doc 3, Testing Slide # 20

   public void testPushAndFull() {
      Stack test = new Stack(5);
      assert("Is empty", test.isEmpty() );
      assert("Empty stack claims full", test.isFull() == false);
      for (int k = 1; k <=5;k++)
         test.push( k);
      assert("Should not be empty", test.isEmpty() == false);
      assert( "Is full", test.isFull() );
      try {
         test.push( 6);
         fail("Full stack accepted element");
      }
      catch (Exception overflow) {
      }
   }
   public void testPushPop() {
      Stack test = new Stack(5);
      for (int k = 1; k <=5;k++)
         test.push( k);
      for (int k = 5; k >= 1; k--)
         assert( "Pop fail on element " + k,  test.pop() == k);
   }
}

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