1. Introduction to Testing, SUnit and Error Handling
CS2340
Fall 2004

2. Blackbox Testing Going to get the theory from 2335.
Treat code as a “black box”
Base test cases on specification
Two major techniques:
Equivalence Partitions
Boundary Value Tests
Exhaustive testing not possible
Fall 2004

3. Equivalence Partitions
Treat sets of data as same (if one test succeeds all tests succeed)
For ranges, pick one test in range, one test on each end.
For sets, pick one in set, one not in set.
For unique values, pick value, not value.
Fall 2004

4. Examples Must accept years between 1-2050. Test cases: 0, 1876 , 2076.
Passwords must be 6-8 chars long:
Test cases: ab, abcdef, abcdegujswidn
Leap years are divisible by four:
Test cases: 16, 99
Phone exchanges must not begin with 555.
Test cases: 555, 498
Fall 2004

5. Boundary Value Tests
Most of the errors happen on the boundaries between sets
Must accept years between
Test cases: 0, 1, 2050, 2051.
Boundary Value Tests compliment Equivalence Partitions
Fall 2004

6. Writing your tests
We could just write workspace code and DoIt over and over…
Hoping that we don’t ever close window
Checking transcript manually to ensure results are what we want.
We could write a custom class to do our test and result checking
We can use the SUnit framework.
Fall 2004

7. SUnit
Testing framework for creating and running unit tests (regression tests) automatically in Smalltalk
Originally developed by Kent Beck
Implementations exist for many languages
JUnit for Java
A framework is a collection of classes that can be used and extended for a particular domain.
Fall 2004

8. SUnit Advantages Self-checking and reporting
Check results against expected results
Report which test is broken
Built-in initialize before a test and clean-up after a test
setUp is called before each method test
tearDown is called after each method test
Fall 2004

9. When to use SUnit? Extreme Programming Used for regression testing
Create unit test before the code
Helps you understand what the code must do
Helps you to know when the code is done
Used for regression testing
Did you break anything when making changes?
Maintenance
Once you find a bug create a unit test to make sure it is fixed and stays fixed
Fall 2004

10. Using SUnit Derive class from TestCase
Do any set up (initialize variables) in setUp
Do any clean up in tearDown
Create methods testXxxx
Use:
self assert: expr_that_evals_true
self deny: expr_that_evals_false
self should: [ block that evals to true ].
self shouldnt: [block that evals to false ].
TestRunner open.
Fall 2004

11. TestRunner
You can look at the current tests in Squeak using TestRunner and run any by clicking on “Run”. There is an example ExampleSetTest to learn from.
Fall 2004

12. Example: Assume we have a class Muppet with method: name: aName
And:
name
testName
| oscar |
oscar := Muppet new.
oscar name: 'oscar'.
self assert: oscar name = ’oscar'.
self should: [oscar name = ’oscar'].
self deny: oscar name = ’ocsar'.
TestCase subclass: #TestMuppet
instanceVariableNames: ‘ ‘
classVariableNames: ‘ ‘
poolDictionaries: ‘ ‘
category: ‘Muppet Classes’ .
Fall 2004

13. Key steps
For each ‘real’ class X, have a test class TestX derived from TestCase
Decide how to test functionality
For functionality Y in class X, have a test method testY in class TestX.
Run TestRunner to evaluate tests automatically (TestRunner open)
May use SqueakMap to download TestBrowser if desired (more later)
By ‘real’ class we mean a class that represents something in the domain or a model class. You don’t have to have a test per method but you do want to test important functions.
Fall 2004

14. Testing Set Functionality
Notice that not every method of Set has a test method. The main functionality that is being tested is add, grow, includes, remove, no duplicates, and exceptions.
Fall 2004

15. Testing with Exceptions
Check for exceptions
self should: [boolean] raise: Exception
Make sure no exceptions
self shouldnt: [boolean] raise: Exception
Fall 2004

16. Exception Handling in Squeak
Class Exception and its subclasses provided for use.
Can emulate try/catch block in other languages
Exceptions pass up inheritance hierarchy. If not handled, get default handler at Object.
Look at the hierarchy to see the subclasses of Exception including predefined exceptions like ZeroDivide
Fall 2004

17. [x / y] “like a try block” on: ZeroDivide “exception class”
Example
| x y |
x:=7. y:=0.
[x / y] “like a try block”
on: ZeroDivide “exception class”
do: [ :exception |
Transcript show:
exception description ; cr. 0 ].
This basically means execute the code in the block with an exception handler. If the exception occurs during the code execution and an object of the class given on the on: is created then execute the code in the do: block.
Fall 2004

18. Example | f | [f:=FileStream fileNamed: 'fred'. f nextPutAll: 'Test'.
f close. ]
on: FileDoesNotExistException
do: [:exception |
Transcript show: exception description. ].
Fall 2004

19. Example: Testing with Exceptions
Fall 2004

20. SqueakMap Software package distribution mechanism with Squeak
World Menu -> Open… -> Package Loader
Asks if you want to install SqueakMap; say yes
Eventually fires up SM Package Loader
Fall 2004

21. Package Loader Select “TestBrowser” in SqueakMap
Right-click, choose “install” from menu
Fall 2004

22. TestBrowser
TestBrowser open
Fall 2004

23. Next on the Menu Read chapter 3 “Joe the Box” – simple 2D graphics UML
Fall 2004