SUnit: Unit Tests in Pharo

Agile Programming

Pharo programming culture adheres to agile programming

• Incremental, early feedback
• Be prepared for changes
• Driven by human
• Supported by automated tests

SUnit

• Extremely simple (4 classes)
• Originally developed by K. Beck (agile programming father)
• Got copied all over the places

A Test

In a test, we

• Create a context: Create an empty set
• Send a stimulus: Add twice the same element
• Check the results: Check that the set contains only one element

Set TestCase

TestCase subclass: # SetTestCase
    ...

SetTestCase >> testAdd 
  | empty |
  empty := Set new.   "Context"
  empty add: 5.   "Stimulus"
  empty add: 5.
  self assert: empty size = 1.   "Check"

SetTestCase run: #testAdd

In a Subclass of TestCase

Each method starting with test*:

• Represents a test
• Is automatically executed

The results of the test are collected in a TestResult object

Another Example

testAdjacentRunsWithEqualsAttributesAreMerged
  "this demonstrates that adjancent runs with equal attributes are merged. "
  | runArray |
  runArray := RunArray new.
  runArray
    addLast: TextEmphasis normal times: 5;
    addLast: TextEmphasis bold times: 5;
    addLast: TextEmphasis bold times: 5.
  self assert: (runArray runs size = 2).

Failures and Errors

• A failure is a failed assertion, i.e., an anticipated problem that you test
• An error is a condition you didn't check for

To Test That an Error Must Be Raised

SetTestCase >> removeElementNotInSet
  self 
    should: [ Set new remove: 1 ] 
    raise: NotFound

To Test That an Error Must Not Be Raised

SetTestCase >> removeElementNotInSet
  self 
    shouldnt: [ Set new add: 1 ] 
    raise: NotFound

Duplicating the Context

SetTestCase >> testOccurrences
  | empty |
  empty := Set new.
  self 
    assert: (empty occurrencesOf: 0) 
    equals: 0.
  empty add: 5; add: 5.
  self 
    assert: (empty occurrencesOf: 5) 
    equals: 1

• empty := Set new. is repeated between tests
• We can factor it out

setUp and tearDown Messages

• Executed systematically before and after each test run
• setUp allows us to specify and reuse the context
• tearDown to clean after

Defining a setUp Method

SetTestCase >> setUp
  empty := Set new

setUp is executed for you before any test execution

SetTestCase >> testOccurrences
  self 
    assert: (empty occurrencesOf: 0) 
    equals: 0.
  empty add: 5; add: 5.
  self 
    assert: (empty occurrencesOf: 5) 
    equals: 1

SUnit Core

TestSuite, TestCase and TestResult

• A TestCase represents one test
  • e.g. the method: SetTestCase >> testOccurenceOf
• A TestSuite is a group of tests
  • SUnit automatically builds a suite from the methods starting with 'test*'
• A TestResult represents a test execution results

Test Resources

• A TestResource is an object which is needed by a number of Test Cases, and whose instantiation is so costly in terms of time or resources that it becomes advantageous to only initialize it once for a Test Suite run.

• A TestResource is invoked once before any test is run. (read Pharo by Example SUnit Chapter)

What You Should Know

• How to write simple tests
• Reuse a bit the context by defining setUp methods

Summary

• Unit tests are easy to create and run
• Create one test and run it million times!
• Use them as your life insurance
• There exists other libraries for Mock (BabyMock) or different styles of testing