1. Unit Testing Part 2: Drivers and Stubs
CSIS 3701: Advanced Object Oriented Programming

2. Testing Support Classes
Support class not executable program
Need another executable program to run tests
Construct support objects
Call methods
Display/check object state for correctness
Key: other “tester” program must be simple
Any errors must be in support class, not tester!

3. NameList Example NameList.java Main.java Are errors here?
Current application may not use all methods in class
NameList.java
Main.java
Stores names
Returns current names
Validates list not full, name not already in list
names
Are errors here?
Or are they in the testing tool itself?

4. Drivers Simple program to test other code
Example: function driver for C++ sqrt function int main() { double test; while(1) { cout << “Enter test case: “; cin >> test; cout << sqrt(test) << ‘\n’; } }

5. main method to test these
Class Drivers in Java
Must be in a main method
Separate testing class
As main in support class itself
Idea: keep testing tools as part of class
Do not delete when finished testing
Will need again if class modified in future
NameList.java
Constructors
and methods
main method to test these

6. Class Drivers in Java public static void main(String[] args) {
Example: Simple driver for add method in NameList
public static void main(String[] args) {
NameList n = new NameList(3);
while(true) {
String name = JOptionPane.showInputDialog(null, "Enter name");
n.add(name);
JOptionPane.showMessageDialog(null, n.toString()); }

7. Class Drivers in Java public static void main(String[] args) {
May need additional code for exceptions
public static void main(String[] args) {
NameList n = new NameList(3);
while(true) {
String name = JOptionPane.showInputDialog(null, “Name:");
try {n.add(name);}
catch (FullListException ex) {
JOptionPane.showMessageDialog(null, "List full!"); }
catch (InListException ex) {
JOptionPane.showMessageDialog(null, “In list!");
JOptionPane.showMessageDialog(null, n.toString());

8. Class Dependency What if your class depends on other classes?
May not be available immediately if being developed by others
Still need to compile and test your code
Cannot afford to wait around for others!
Example: Developing main visual application without working NameList class

9. Class Dependency Main.java NameList.java This class does not exist yet
NameList constructor
void add(String)
int getSize() String getNameByIndex(int)
boolean isIn(String)
boolean isFull()
NameList names
This class does not exist yet
Nor do these constructors or methods

10. NameList Example None of the following code will work! else {
public void actionPerformed(ActionEvent e) {
String name = nameField.getText();
if (names.isIn(name))
JOptionPane.showMessageDialog(this, name + " already in list");
else {
names.add(name);
for (int i = 0; i < names.getSize(); i++)
namesArea.append(names.getNameByIndex(i) + "\n");
if (names.isFull()) addButton.setEnabled(false); }

11. Stubs Stub: temporary code to take place of code still in development
Replaced with actual code when available
Must allow thorough testing of your code
All methods, branches, etc.
Must be simple
Easy to create
Unlikely to contain own bugs

12. Stub Function Example Simple C++ example: void function() {}
Your code: …
function(); …
stub code:
void function() {}
Function written by other developer and not currently available
Simplest possible stub – will allow your code to compile and run

13. Stub Function Example Can include diagnostic messages to help test
Is external function called at correct time?
Is it called with correct parameters?
Your code: …
function(a); …
stub code:
void function(int x) { cout << “function called with “ << x << “ as parameter\n”; }
Diagnostic message displayed

14. Stub Function Example May need to return value to help test your code
Can be simple “hard wired” value
Can prompt for return value if needed to test branches
int function(int x) { cout << “function called with “ << x << “ as parameter\n”;
cout << “What should it return?”;
int y;
cin >> y;
return y; }
b = function(a);
if (b > 0) { … } else {…}
function must return values greater than and less than 0 to test both branches
Can perform one test that returns 1 and another that returns -1

15. Stub Classes Takes place of entire class during testing
No state variables
Stubs for constructors/methods called by your code
Example: NameList stub for testing main:
Stub NameList constructor  display parameter
Stub add method  display parameter, prompt for whether to throw exception
Stub getSize method  prompt for int to return
Stub isIn method  prompt to return true or false
Stub isFull method  prompt to return true or false
Stub getNameByIndex method  return dummy value

16. NameList Stub public class NameListStub {
public NameListStub(int max) {
System.out.println("constructor called with "+max); }
public String getNameByIndex(int index) {
return "Stub Name";
public int getSize() {
String response = JOptionPane.showInputDialog(null, "What is list size?");
return Integer.parseInt(response);

17. NameList Stub public boolean isIn(String name) {
String response = JOptionPane.showInputDialog(null, "Is "+name+" in list?");
return response.equals("true"); }
public boolean isFull() {
String response = JOptionPane.showInputDialog(null, "Is list full?");

18. NameList Stub public void add(String name) {
System.out.println("add called with "+name); String response = JOptionPane.showInputDialog(null, “1) No exception\n2 List full\n3) In list"); if (response.equals(“1”)) return; if (response.equals(“2”)) throw new FullListException(); if (response.equals(“3”)) throw new InListException(); }
Prompt for whether to throw an exception
Throw appropriate exception type (must have stubs for these also)!