SDSU CS 580 Client-Server Programming
Fall Semester, 2000
Testing
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© 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

Tests individual code segments
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

  • 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


Shows list of previously run test classes


JUnit has two class loaders


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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2000 SDSU & Roger Whitney, 5500 Campanile Drive, San Diego, CA 92182-7700 USA.
	
 OpenContent license defines the copyright on this document.





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