Testing: TDD, BDD, WTH?

Timothy Lim / @thewheat Slides: http://thewheat.github.io/presentation-testing-tdd-bdd-wth

Tests: Not just the thing you did in school

• What is Testing To You?
  • Ensuring code does what it is meant to do
  • Ensuring system works as expected
  • Being able to manually test things
• What is your current testing strategy?
  • Code and hope it works?
  • Code locally, test, push to production and retest?
  • Staging Environments?
• Are you confident in your build?

TDD: Test Driven Development

BDD: Behaviour Driven Development

• Philosophy / Definition
  • Focuses on clear understanding of software behavior from stakeholders
  • Focuses on why code should be created: thinking "from the outside in"
  • Extends TDD: tests written in natural language that non-programmers can read
• Can be used as Acceptance Tests
  • Given [initial context],   when [event occurs],   then [ensure some outcomes]
  • Given: I am at the login page
  • When: I enter valid credentials
  • Then: I should be logged in and see the "logout" link

Different types of tests

• There are many but will focus on 3
• Unit Tests
  • Testing core unit of works
  • Isolated: no interaction with other systems (e.g. databases, web services)
• Integration Tests
  • Test the integration between 2 different "units" / systems (e.g. your core system and the database / web service)
  • Database interaction: test database or in-memory databses (H2 / SQLite)
• Functional Tests
  • Tests features / functions of a system from user's point of view (Quality Assurance process. Black box testing)
  • Automation tools (Selenium for webapps)

Where to Start?

Test Suites / Frameworks

• Unit & Integration Testing
  • JUnit (Java)
  • Nunit (C#)
  • RSpec (Ruby)
  • QUnit (Javascript)
  • Mocha (Javascript)
  • PHPUnit (PHP)
  • Unittest (Python)
• BDD specific
  • Cucumber (Java / Ruby on Rails / Javascript)
  • SpecFlow (C#)
  • Jasmine (Javascript)
  • CasperJS (Javascript)
  • behave (Python)

Structure of Testing Functions

• Runs once before any tests have run
• E.g. create database schema

• Runs each time before any test
• E.g. clear & populate database / state

• Actual test to run: Assert something

• Runs each time after any test
• E.g. clear database / state

• Runs once after all tests are run
• E.g. drop database schema

Testing Concepts (1/3)

• Test (Test Fixture)
  • Actual test to run
  • Assert something

  @Test
  addTwoPositiveNumbers(){
      calc = new Calculator();
      output = calc.add(1,2);
      Assert.Equal(3, output);
  }
  

  @Test
  primeNumberIsCorrectlyDetected(){
      calc = new Calculator();
      output = calc.isPrime(2);
      Assert.IsTrue(output);
  }
  

Testing Concepts (2/3)

• TestDouble like movie doubles, who perform stunts instead of real movie actors
• Types:
• Dummy
• Fake
• Stubs
• Spies
• Mocks

Testing Concepts (3/3)

• Mocks
  • Simulated objects that mimic the behavior of real objects
  • Steps:
  • Create a mock object
  • Define behaviour
  • Call or test behaviour

  // mock a concrete class
  LinkedList mockedList = mock(LinkedList.class); 
  
  //stubbing - before execution
  when(mockedList.get(0)).thenReturn("first");
  
  //folloing princs "first"
  System.out.println(mockedList.get(0));
  
  //following prints "null" because get(999) as not stubbed
  System.out.println(mockedList.get(999)); 
  
  // Source: Mockito 
                                      

Functional Testing Concepts

• Page Object Pattern
  • A pattern that:
    • reduces code duplication
    • makes tests more readable and robust
    • makes tests more maintanable
  • They represent the services offered by a particular page    i.e. models the 'page' for your test to interact with
  • They should be the only thing that has a deep knowledge of the structure of the HTML of a page    i.e. changes to interface / platform (e.g. web to native), should only affect page object: other parts of tests stay the same

Functional Testing Concepts with Cucumber (1/3)

• Available on many platforms
• Utilizes Gherkin syntax
  • Business Readable, Domain Specific Language
  • Provides for both documentation and automated tests
  • Single Gherkin source file contains a description of a single feature
  • .feature file extension

Functional Testing Concepts with Cucumber (2/3)

 1: Feature: Some terse yet descriptive text of what is desired
 2:   Textual description of the business value of this feature
 3:   Business rules that govern the scope of the feature
 4:   Any additional info that will make the feature easier to understand
 5: 
 6:   Scenario: Some determinable business situation
 7:     Given some precondition
 8:       And some other precondition
 9:      When some action by the actor
10:       And some other action
12:      Then some testable outcome is achieved
13:       And something else we can check happens too
14: 
15:   Scenario: A different situation
16:       ...    

Functional Testing Concepts with Cucumber (3/3)

• Convert readable text to actual code / interactions
• With the correct plugins: Ctrl+Click step in .feature file to set up the function

Things to note

• Browser tests
  • Beware the ajax loads and templates
  • sleep() if you must, but it's not ideal: implicitlyWait() could be the answer
  • Different environments respond differently on the same hardware
• Code Coverage
  • How much of your code is tested?
  • Quantity (100% coverage) is not a replacement for Quality or thoughtfulness
• Testing is not the end all and be all

In conclusion

• Testing is great
• Helps speed development
• Helps ensure that your code works
• Peace of mind while refactoring

THE END