1. COMP 103 Testing with JUnit 2016-T2 extras
Marcus Frean, Rashina Hoda, and Peter Andreae
School of Engineering and Computer Science, Victoria University of Wellington
2016-T2 extras

2. How can we test a program?2
How to test a program?
Test the program as a whole?
Test all classes separately?
 both!
Testing a class separately
Need to create instances of the class and call methods on it
May need set up code to fill the fields of the instance objects
Should test all methods
Should test methods under different situations
Should report on the errors it finds
 would normally require writing a test program

3. eg: testing a Collection3
May use a test program with a main method
public class ArrayListTest {
public static void main(String args) {
UI.println("Testing ArrayList…");
List<String> list = new ArrayList<String>();
if (! list.isEmpty() ) UI.println(" *** New list is not empty");
if (list.size() !=0 ) UI.println(" *** New list has a size != 0 ");
for (int i=0; i<20; i++) { list.add(i, "v"+i); }
for (int i=0; i<20; i++) {
if ( ! list.get(i).equals("v"+i) )
UI.printf(" *** %d'th value of list should be v%d", i, i);
if ( list.size() != 20 )
UI.println(" *** List size should be 20 after adding 20 values"); :

4. JUnit documentation 4

5. JUnit makes testing easier5
A special class Assert, with special methods made for testing
assertTrue("The new list should be empty.", myList.isEmpty());
assertFalse("After adding, list should not be empty.", myList.isEmpty());
assertEquals("Size should be 1.", myList.size(), 1);
assertNull("Item 10 should be null.", myList.get(10));
The 1st argument is the message to display if test fails.
test methods can be run automatically
BlueJ has dedicated Junit support

6. The necessary ingredients6
To define a Junit class we need
import static org.junit.Assert.*;
import org.junit.Before;
import org.junit.Test;
import org.junit.After;
import org.junit.runner.JUnitCore;
and then
before a “setup” method, e.g. make an empty Set
before each test method
We don’t need to unless we need to “clean up”
See ArraySetTestCore.java (and ...Completion.java) for examples

7. Using JUnit public class ArrayListTest {7
public class ArrayListTest {
private List<String> list;
@Before public void initialiseEmptyList() { list = new ArrayList <String>(); } @Test public void testIsEmptyOnEmptyList() {
assertTrue("A new list should be empty", list.isEmpty()); }
@Test public void testAdd() {
for (int i = 0; i < 20; i++) {
String value = "v" + i;
list.add(value);
assertFalse("List should not be empty after add", list.isEmpty());
assertEquals("Size should be larger after add", (i+1), list.size());
assertEquals("Item should be in list", value, list.get(list.size()-1));

8. BlueJ knows about JUnit tests8

9. BlueJ displaying test results9
test could not be executed
test failed