Why BDD?

Typical Test

@Test
public void shouldInsertPetIntoDatabaseAndGenerateId() {
    Owner owner6 = this.clinicService.findOwnerById(6);
    int found = owner6.getPets().size();

    Pet pet = new Pet();
    pet.setName("bowser");
    Collection<PetType> types = this.clinicService.findPetTypes();
    pet.setType(EntityUtils.getById(types, PetType.class, 2));
    pet.setBirthDate(new DateTime());
    owner6.addPet(pet);
    assertThat(owner6.getPets().size()).isEqualTo(found + 1);

    this.clinicService.savePet(pet);
    this.clinicService.saveOwner(owner6);

    owner6 = this.clinicService.findOwnerById(6);
    assertThat(owner6.getPets().size()).isEqualTo(found + 1);
    // checks that id has been generated
    assertThat(pet.getId()).isNotNull();
}
  

Issues with typical tests

• Many technical and often irrelevant details
• Point of the test often hard to grasp
• Code duplication
• Can only be read by developers
• Cannot be used as documentation

Behavior-Driven Development

• Behavior is described in a common domain language understandable by domain experts
• Domain experts and developers collaborate on defining the behavior
• Executed like normal tests
• Creates a living documentation

BDD Example

  Scenario: Pets can be assigned to pet owners

   Given a pet owner
     And a dog
    When assigning the pet to the pet owner
    Then the pet owner owns an additional pet
 

BDD in Java

"Classical" BDD Frameworks

• Cucumber: Plain Text + Java
• JBehave: Plain Text + Java
• Concordion: HTML + Java
• Fitness: Wiki + Java

Additional maintenance cost

Developer-friendly BDD Frameworks

• Spock: Groovy
• ScalaTest: Scala
• Jnario: Xtend
• Serenity*: Java

Stack Overflow?

Goals

• Developer friendly (low maintenance overhead)
• Readable test code (Given-When-Then)
• Modular and reusable test code
• Reports for domain experts

Demo

Scenarios in JGiven

import org.junit.Test;
import com.tngtech.jgiven.junit.ScenarioTest;

public class FindOwnerTest
       extends ScenarioTest<GivenOwner, WhenSearching, ThenOwner> {

    @Test
    public void owners_can_be_found_by_last_name() {

        given().an_owner_with_last_name("Smith");

        when().searching_for("Smith");

        then().exactly_the_given_owner_is_found();
    }
}
      

Stage Classes

@JGivenStage // only needed when using Spring
public class WhenSearching extends Stage<WhenSearching> {

    @Autowired
    ClinicService clinicService;

    @ScenarioState
    Owner owner;

    public WhenSearching searching_for(String name) {
       owner = this.clinicService.findOwnerByName(name);
       return this;
    }
}
          

Console Output

           Owners can be found by last name

             Given an owner with last name "Smith"
              When searching for "Smith"
              Then exactly the given owner is found

HTML5 App

• jgiven.org/jgiven-report/html5/ (Local)
• https://github.com/mthuret/xke-jgiven (Local)

Practical Experience

• 3 years of experience in a large Java Enterprise project (up to 70 developers)
• Over 3000 Scenarios
• Readability and reusability of test code has been greatly improved
• Maintenance costs of automated tests have been reduced (no hard numbers)
• Well accepted by developers
• Easy to learn by new developers
• Developers and domain experts collaborate using scenarios

Further Features

Parameterized Scenarios

@Test
@DataProvider({
   "Smith, 1",
   "Davis, 0",
   "Sm, 1"})
public void should_find_owner_by_last_name( String searchTerm, 
	                                    int numberOfResults ) {

    given().an_owner_with_last_name("Smith");

    when().searching_for(searchTerm);

    then().exactly_$_owner_is_found(numberOfResults);
}

Parameterized Scenarios

Console Output

 Should find owner by last name

   Given an owner with last name Smith
    When searching for <searchTerm>
    Then exactly <numberOfResults> owner is found

  Cases:

   | # | searchTerm | numberOfResults | Status  |
   +---+------------+-----------------+---------+
   | 1 | Smith      |               1 | Success |
   | 2 | Davis      |               0 | Success |
   | 3 | Sm         |               1 | Success |

Parameterized Scenarios

HTML Report

Parameter Formatting

• Default: toString()
• @Format( MyCustomFormatter.class )
• @Formatf( " -- %s -- " )
• @MyCustomFormatAnnotation

Example

@OnOff

@Format( value = BooleanFormatter.class, args = { "on", "off" } )
@Retention( RetentionPolicy.RUNTIME )
@interface OnOff {}

public SELF the_machine_is_$( @OnOff boolean onOrOff ) { ... }

given().the_machine_is_$( false );

Given the machine is off

@BeforeScenario und @AfterScenario

public class GivenSteps extends Stage<GivenSteps> {

    @ProvidedScenarioState
    File temporaryFolder;

    @BeforeScenario
    void setupTemporaryFolder() {
        temporaryFolder = ...
    }

    @AfterScenario
    void deleteTemporaryFolder() {
        temporaryFolder.delete();
    }
}
          

@ScenarioRule

public class TemporaryFolderRule {
    File temporaryFolder;

    public void before() {
        temporaryFolder = ...
    }

    public void after() {
        temporaryFolder.delete();
    }
}

public class GivenSteps extends Stage<GivenSteps> {
    @ScenarioRule
    TemporaryFolderRule rule = new TemporaryFolderRule();
}
          

@AfterStage, @BeforeStage

public class GivenCustomer extends Stage<GivenSteps> {
    CustomerBuilder builder;

    @ProvidedScenarioState
    Customer customer;

    public void a_customer() {
        builder = new CustomerBuilder();
    }

    public void with_age(int age) {
        builder.withAge(age);
    }

    @AfterStage
    void buildCustomer() {
        customer = builder.build();
    }
}
          

Tags

@Test @FeatureEmail
void the_customer_gets_an_email_when_ordering_a_book() {
   ...
}

@Test @Story( "ABC-123" )
void the_customer_gets_an_email_when_ordering_a_book() { ... }

@Pending

• Marks whole scenarios or single steps as pending
• Steps are skipped and marked accordingly

HTML Report

@Hidden

• Marks methods to not appear in the report
• Useful for technical methods

@Hidden
public SELF doSomethingTechnical() { ... }

Extended Step Descriptions

@ExtendedDescription("The Hitchhiker's Guide to the Galaxy, "
                   + "by default the book is not on stock" )
public SELF a_book() { ... }

HTML Report

Attachments

public class Html5ReportStage {
    @ExpectedScenarioState
    protected CurrentStep currentStep; // provided by JGiven

    protected void takeScreenshot() {
        String base64 = ( (TakesScreenshot) webDriver )
            .getScreenshotAs( OutputType.BASE64 );
        currentStep.addAttachment(
            Attachment.fromBase64( base64, MediaType.PNG )
                      .withTitle( "Screenshot" ) );
    }
}

HTML Report

Inline Attachments

Summary

• Developer friendly
• Highly modular and reusable test code
• Just Java, no further language is needed
• Easy to integrate into existing test infrastructures (JUnit, TestNG)
• Open Source (Apache 2 Licence)
• Maven and Jenkins plugins
• Nice reports for domain experts
• Domain experts can not write scenarios in JGiven
  (But they can write them in any other format and developers can easily translate them to JGiven)

BDD without the hassle!