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Lab on Unit

Lab on Unit

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L2624 labriola L2624 labriola Presentation Transcript

  • Unit Testing ActionScript and Flex
    Michael Labriola | Senior Consultant, Digital Primates
    @mlabriola | labriola@digitalprimates.net
  • Who Am I?
    Michael Labriola
    Senior Consultant
    Digital Primates
    Client side architect specializing in Adobe Flex
    Architect and developer of Fluint
    Lead architect and developer of FlexUnit4.x
    Benevolent Dictator of the Spoon Framework
    Co-Author of Flex Training from the Source Series
    Team Mentor
    Fan of working code
    2
  • Before We Begin
    This lab is broken into five main tasks with various exercises along the way
    In 90 minutes, if things go well, we will complete tasks one through four with some discussion along the way
    Task five is something I would strongly advise you take a bit of time to review later.
    It is a full rework of the application to be testable.
    The lab workbook and all lesson files are available for download
    At the end of several lessons there are ‘Advanced’ exercises.
    People will move at different rates through the content.
    If you find yourself done with a Task and have time, ponder the advanced exercise they will help demonstrate points in a Socratic way
    They can be treated as thought exercises but work better if you actually try to implement
    3
  • Types of Testing - Unit
    Unit Testing - Our concern in this lab
    Unit testing involves testing the smallest units of code
    A single object
    It requires that the object be isolated.
    The test result should not be able to be affected by other objects
    It should not be affected by global state
    When a unit test fails the source of the error should be immediately clear
    This requirement for isolation means that some code cannot be unit tested
    Axiom - You can only unit test testable code
    Creating testable code is both a question of implementation and of architecture
    Many people want to unit test but fail
    In my experience, this is usually because the code they wish to test is not testable in units
    4
  • Types of Testing - Integration
    Integration Testing
    Involves testing several (ideally tested) units together
    Very important part of testing
    You need to know that individual objects work together properly
    Failures are not as clear
    When an integration test fails, there are (n) places it could have failed
    As a general rule, the moment we discuss any of the following words, we are discussing some form of integration test:
    Asynchronous
    Server
    Lifecycle
    DisplayList
    5
  • Types of Testing - Functional
    Allows you to record and playback interactions with an application
    Extremely important; ensures that the application works to specification
    Many units need to be working before you can produce a single test
    Failures are very unclear
    Any number of units could be responsible for the failure
    Many tools available:
    Flex Monkey – Open Source
    Test Complete
    RIATest
    HP QTP
    And more
    6
  • Exercise 1.1
    7
  • Object Graphs
    To understand unit testing we need understand object graphs
    There are two types of objects we are concerned about Branch and Leaf
    Leaf Nodes have no dependencies on other objects in your code (they will have dependencies on simple types and some flash player objects)
    Trivial to test
    Branch Nodes have dependencies on other objects
    More difficult and sometimes impossible to test
    8
  • Creating Objects
    You will always have both types in your system, however, we often have too many dependencies because we forget some simple things:
    An object is supposed to have one responsibility.
    Single Responsibility Principle.
    Objects with (n) responsibilities will be much harder to test effectively
    Second objects shouldn’t reach into each other.
    It breaks encapsulation
    Don’t violate the Law of Demeter
    myObject.childObject.grandChildObject.property
    9
  • Exercise 1.2 and 1.3
    10
  • Testing Framework
    FlexUnit 4 is a unit testing framework
    You don’t need a framework to test
    You already test each time you walk through the same actions to vet a piece of code
    Testing frameworks only exist to:
    Automate this effort so the tests can be run again and again easily
    Standardize the way tests are constructed so they are understandable to others
    11
  • Assertions
    Assertions are a tool used to reveal whether or not a piece of code is working as expected.
    They take the form of a strong statement indicating the result. For example, if you add the numbers 2 and 3.
    result = 2 + 3;
    You can assert that the result is 5. You do so as you are sure that no other answer is satisfactory and that a different answer is just plain wrong.
    assertEquals( 5, result );
    If this assertion is not true, meaning that result is not equal to 5, then you can conclude that the plus operator no longer works correctly in all cases. This is the basis of testing.
    12
  • Test
    A Test is just a public method of an object
    The method is decorated by a special [Test] metadata which allows FlexUnit 4 to recognize it as test
    [Test]
    public function shouldSeeBlueSky():void {
    varsky:Sky = new Sky();
    assertEquals( “blue”, sky.color );
    }
    Tests contain one (preferable) or more assertions indicating your belief about the state of the object under test or the result of a method invoked on the object
    Each test is discrete. It should not depend on other tests or the order the tests are run.
    13
  • Test Case
    A Test Case is a collection of related Tests in a single class
    [Test]
    public function shouldSeeBlueSky():void {
    varsky:Sky = new Sky();
    assertEquals( “blue”, sky.color );
    }
    [Test]
    public function shouldNotSeeClouds():void {
    varsky:Sky = new Sky();
    assertNull(sky.clouds);
    }
    14
  • Test Case Setup
    As all tests in a single Test Case should be related, they often can share setup
    The combination of the setup/environment needed to run a test is called a Test Fixture
    FlexUnit 4 facilitates sharing test fixtures by allowing you to mark a method with Before or After metadata. This indicates the method should be run before or after every test method.
    [Before]
    public function andTheSkyWasCreated():void {
    sky = new Sky();
    }
    [After]
    public function letItFall():void {
    sky = null;
    }
    15
  • Test Case Rules
    FlexUnit 4 offers one more way to configure the test case fixture, rules.
    You can think of rules as a way to move things that would happen in the Before and After into a separate object.
    This makes it easier to share this configuration code amongst multiple test cases
    [Rule]
    public varcreateAndDestroySky:CreateAndDestroySkyRule = new CreateAndDestroySkyRule();
    16
  • Test Suite
    A Test Suite is a collection of Test Cases and other Test Suites
    package flexUnitTests {
    [Suite]
    [RunWith("org.flexunit.runners.Suite")]
    public class CurrencyConverterSuite {
    public var test1:ClearSkyTests;
    public var test2:StormySkyTests;
    }
    }
    17
  • Exercise 2.1 and 2.2
    18
  • Matchers
    The process of performing multiple assertions can become complicated
    Imagine a scenario where you need to verify that 2 points are identical
    [Test]
    public function shouldBeTheSamePoint():void {
    assertEquals( pt1.x, pt2.x );
    assertEquals( pt1.y, pt2.y );
    assertEquals( pt1.z, pt2.x );
    }
    At some point your test cases become littered with all of the work required to do the assertions
    To address this problem, FlexUnit works with something called matchers that allow you to move this work into a separate object
    19
  • Hamcrest
    Using matchers, the code can look more like this:
    [Test]
    public function shouldBeTheSamePoint():void {
    assertThat( pt1, isSamePoint( pt2 ) );
    }
    The code becomes more readable and the matching logic is contained elsewhere.
    There is a collection of matchers that can be used with FlexUnit as well as any ActionScript project that can use specialized matching, it is called Hamcrest-as3
    For more information: https://github.com/drewbourne/hamcrest-as3
    20
  • Exercise 2.3
    21
  • Exercise 3.1-3.2
    22
  • Branches versus Nodes
    We talked about branches in the abstract, but here is something more concrete.
    Even though we extracted the PercentChangeFormatter from MarketInfo, it is still a branch node, not a leaf node
    23
    MarketInfo
    PercentChangeFormatter
    NumberFormatter
  • Combinatorial
    If you aren’t careful with these sorts of dependencies, you end up with combinatorial tests.
    This results in a lot of test duplication… technically this is because you can’t identify independent variables.
    The PercentChangeFormatter really just modifies the String returned from the NumberFormatter a little.
    As they exist now we really end up testing the both of these objects together… which is an integration test…
    24
    PercentChangeFormatter
    NumberFormatter
  • Exercise 4.1
    25
  • Seams and Mocks
    The cleanest way to deal with this is to create a seam.
    If we provide the needed NumberFormatter to the PercentChangeFormatter, we create a seam
    What can we do with that seam?
    We could build the PercentChangeFormatter with a substitute NumberFormatter
    This will eliminate the combinations and allow us to test only one class (a unit)
    There are two types of substitutes we can use… fakes and mocks
    Fakes are just dumb objects that conform to the same interface
    Mocks are intelligent objects that keep track of what happened to them and know how they should respond
    For this Task we will use one of many available mocking frameworks, named Mockolate.
    26
  • Exercise 4.2
    27
  • Additional Resources
    28
    Google Testing Blog
    http://googletesting.blogspot.com/
    FlexUnit
    http://flexunit.org/
    FlexUnit Tutorials
    http://tutorials.digitalprimates.net/flexunit.html
    Hamcrest
    https://github.com/drewbourne/hamcrest-as3
    Mockolate
    http://mockolate.org/
    My Blog
    http://www.digitalprimates.net/author/codeslinger/
  • 29