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Aligning Engineering with Business Value through BDD
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Aligning Engineering with Business Value through BDD



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  • Start by scrubbing the behaviour of the whole application, and continue by specifying the individual parts needed for this behaviour.This approach is called “Outside-In” approach.


  • 1. Aligning Engineering with Business Value through BDD Devesh Chanchlani
  • 2. Test-driven Development • The code should be tested. • Each unit of code should be covered by test. • Each unit of code should be driven by test. (TDD) • Architecture should be arrived through Continuous Design following TDD.
  • 3. TDD Work Flow UT Code Module 1 UT Integration Tests UT UT UT UT Code Module 2
  • 4. Challenges of the Approach • • • • • • • Where to start? What to test? Scope ? What NOT to test? How much to test? How to name your tests? Intent ? Understanding why tests fail? How would the current code bit Assumption fit in the bigger picture? Driven
  • 5. Scope Intent / Motivation Client Driven Intended Behaviour
  • 6. BDD Work Flow 1. Pick a User-Story 2. Specify a Scenario for the User-Story 3. Run the Scenario and watch it fail a) Specify behaviour of the component of the system, in the form of an Example b) Run the example and watch it fail c) Implement minimum functionality to make the example pass 4. Run the scenario, and if it fails, continue with (a) 5. Write another Scenario
  • 7. BDD Work Flow Example User-Story: As a Bank Manager I want to offer reward points to the Credit Card customers So that they feel being valued, and can use the reward points to order various gifts from the shopping portal. Example: Amount Points 0 99 0 100 Scenario : Given a credit card customer When I spend <amount> from my credit card monthly Then I should get <points> reward points. 0 1 999 9 1000 10 1001 10 1500 15 9999 99 10000 100
  • 8. Test Story “RewardPoints.story” Scenario: Amount Spent Rs.0 Given a credit card customer When spends 0 from my credit card monthly Then should get 0 reward points. Scenario: Amount Spent Rs.9999 Given a credit card customer When spends 9999 from my credit card monthly Then should get 99 reward points.
  • 9. Steps import import import import import org.jbehave.core.annotations.Given; org.jbehave.core.annotations.Named; org.jbehave.core.annotations.Then; org.jbehave.core.annotations.When; org.jbehave.core.steps.Steps; public class ExampleSteps extends Steps { Customer customer; int amount; @Given("a credit card customer ") public void givenCustomer() { customer = new Customer(); } @When("spends $amt from my credit card monthly ") public void spendsAmountBy(@Named(“amt") int amount) { customer.setExpenditure(amount); } @Then(" should get $points reward points ") public void thenShouldGetPoints(@Named(“points") int points) { if(customer.getPointsAccrued() != points) throw new RuntimeException(“Customer points wrongly calculated”); } }
  • 10. Test Execution import java.util.Arrays; import java.util.List; import org.jbehave.core.embedder.Embedder; public class SimpleJBehave { private static Embedder embedder = new Embedder(); private static List<String> storyPaths = Arrays .asList(“bank/creditcard/simplejbehave/RewardPoints.story"); public static void main(String[] args) { embedder.candidateSteps().add(new ExampleSteps()); embedder.runStoriesAsPaths(storyPaths); } }
  • 11. The New Approach … UT Code Module 1 UT Integration (Behaviour) Test UT UT UT Code Module 2 Feature UT
  • 12. Contrasting BDD & TDD
  • 13. Thinking in Behavioural Terms TDD  testZeroBill  testRewardPointsRoundingOff  testRewardPointsCalculation BDD  should reward no points when bill is 0  should round off reward points to the floor value  should reward 1 point on every Rs.100 spent Benefits of thinking in “behaviour”:  What to call your test is easy  How much to test becomes clear  Reason of a test failure becomes clearly evident
  • 14. BDD is still TDD • • • • Red-Green-Refactor Test-first programming Design principles and practices Micro-incremental design BDD covers more ground than TDD, although TDD is at its core. BDD is Second-generation Agile methodology, based on • Extreme Programming • Lean Software Development
  • 15. BDD is Multi-Scale Specifications can be described at multiple levels  Top-level can focus on user-interaction  Further down can focus on affected areas that fulfil the higher levels expectations  Even lower we can focus on technical implementation, still with a solid focus on the behaviour
  • 16. Outside-In, Pull-Based TDD UT UT UT UT UT Integration Tests UT Integration (Behaviour) Test UT UT UT UT Feature UT Inside-Out, Push-based UT Outside-In, Pull-based
  • 17. Assumption Driven o Need substantial upfront-design in some kind of modelling tool o Causes waste by decreasing accuracy and increasing rework o Developer may develop more than what the app needed, or miss what was actually required. V/S Client Driven o Forces the developer to prove the value of the design by experiencing it first o Focussed on what you are actually developing o Implement exactly what is needed
  • 18.  BDD creates more harmony between the user story and the Test-Driven Development.  The user stories practices represent analysis and specification in agile projects and TDD represents software design.  Using BDD, devs are able to best consider the interface from the perspective of the consumer of the service rather than as the producer.  BDD aims to bridge the gap between the differing views of computer systems held by Business users and Technologists.
  • 19. Questions …