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Oct 16, 2013

jBehave -- Behavioural Driven Development (BDD)

Q. What is BDD?
A. BDD is principally an idea about how software development should be managed by both business interests and technical insight. Test-driven development focuses on the developer’s opinion on how parts of the software should work. Behavior-driven development focuses on the users’ opinion on how they want your application to behave. So, when you start writing a test, you need to think about the stories, and each story should cover three things:

  • Given :  an input value of 2
  • When : you multiply  the input with 3
  • Then : result should be 6

Even you write unit tests as part of TDD (Test Driven Development) or without TDD , you need to think about Given ... When ... Then ...

Here is a simple  example using the jBehave framework in Java. jBehave tutorial.

Step 1:  Maven pom.xml file on jBehave dependency


 
<dependency>
 <groupId>org.jbehave</groupId>
 <artifactId>jbehave-core</artifactId>
 <version>3.8</version>
</dependency>


Step 2: Define the story in plain English that business users and testers can understand using Given... When Then... style. The math.story file under  src/main/resources/jbehave folder


 
Scenario: 2 squared

Given a variable input with value 2
When I multiply input by 2 
Then result should equal 4

Scenario: 3 squared

Given a variable input with value 3
When I multiply input by 3 
Then result should equal 9



Step 3: Map the above scenarios based stories to Java equivalent.

 
package com.mycompany.jbehave;

import org.jbehave.core.annotations.Given;
import org.jbehave.core.annotations.Named;
import org.jbehave.core.annotations.Then;
import org.jbehave.core.annotations.When;
import org.jbehave.core.steps.Steps;

public class MathSteps extends Steps
{
    private int input;
    private int result;
    
    @Given("a variable input with value $value")
    public void givenInputValue(@Named("value") int value)
    {
        input = value;
    }
    
    @When("I multiply input by $value")
    public void whenImultiplyInputBy(@Named("value") int value)
    {
        result = input * value;
    }
    
    @Then("result should equal $value")
    public void thenInputshouldBe(@Named("value") int value)
    {
        if (value != result)
            throw new RuntimeException("result is " + result + ", but should be " + value);
    }
}


Step 4: Write a main class to excute the scenarios.

 
package com.mycompany.jbehave;

import java.util.Arrays;
import java.util.List;

import org.jbehave.core.embedder.Embedder;

public class JBehaveTest
{
    private static Embedder embedder = new Embedder();
    private static List<String> storyPaths = Arrays
            .asList("jbehave/math.story");
    
    public static void main(String[] args)
    {
        embedder.candidateSteps().add(new MathSteps());
        try
        {
            embedder.runStoriesAsPaths(storyPaths);
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
        
    }
}


Step 5: Run it to get output:

 
Processing system properties {}
Using controls EmbedderControls[batch=false,skip=false,generateViewAfterStories=true,ignoreFailureInStories=false,ignoreFailureInView=false,verboseFailures=false,verboseFiltering=false,storyTimeoutInSecs=300,threads=1]
Running story jbehave/math.story
Generating reports view to 'C:\projects\my-app-parent\my-app\target\jbehave' using formats '[]' and view properties '{defaultFormats=stats, decorateNonHtml=true, viewDirectory=view, decorated=ftl/jbehave-report-decorated.ftl, reports=ftl/jbehave-reports-with-totals.ftl, maps=ftl/jbehave-maps.ftl, navigator=ftl/jbehave-navigator.ftl, views=ftl/jbehave-views.ftl, nonDecorated=ftl/jbehave-report-non-decorated.ftl}'
Reports view generated with 0 stories (of which 0 pending) containing 0 scenarios (of which 0 pending)


Now, modify the math.story file to have an error for the second  scenario as shown below. 3 * 3 is not 10.

 
Scenario: 2 squared

Given a variable input with value 2
When I multiply input by 2 
Then result should equal 4

Scenario: 3 squared

Given a variable input with value 3
When I multiply input by 3 
Then result should equal 10


Run it again with the change, and you will get an error as shown below for the second scenario.

 
Processing system properties {}
Using controls EmbedderControls[batch=false,skip=false,generateViewAfterStories=true,ignoreFailureInStories=false,ignoreFailureInView=false,verboseFailures=false,verboseFiltering=false,storyTimeoutInSecs=300,threads=1]
Running story jbehave/math.story
Generating reports view to 'C:\projects\my-app-parent\my-app\target\jbehave' using formats '[]' and view properties '{defaultFormats=stats, decorateNonHtml=true, viewDirectory=view, decorated=ftl/jbehave-report-decorated.ftl, reports=ftl/jbehave-reports-with-totals.ftl, maps=ftl/jbehave-maps.ftl, navigator=ftl/jbehave-navigator.ftl, views=ftl/jbehave-views.ftl, nonDecorated=ftl/jbehave-report-non-decorated.ftl}'
Reports view generated with 0 stories (of which 0 pending) containing 0 scenarios (of which 0 pending)
org.jbehave.core.embedder.Embedder$RunningStoriesFailed: Failures in running stories: 
jbehave/math.story: org.jbehave.core.embedder.StoryManager$StoryExecutionFailed: jbehave/math.story
 at org.jbehave.core.embedder.Embedder$ThrowingRunningStoriesFailed.handleFailures(Embedder.java:495)
 at org.jbehave.core.embedder.Embedder.handleFailures(Embedder.java:224)
 at org.jbehave.core.embedder.Embedder.runStoriesAsPaths(Embedder.java:205)
 at com.mycompany.jbehave.JBehaveTest.main(JBehaveTest.java:19)



Next post will use junit for testing the scenarios.

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