Behaviour-Driven Development

Transcription

1 Behaviour-Driven Development A road to effective design and clean code Dan North - ThoughtWorks

2 I My name is Dan am a developer I am a coach I am your guide 2

3 Part 1: ineffective design and ugly code 3

4 The The It It The or Project failures - a field guide project comes in too late costs too much to finish application does the wrong thing is unstable in production breaks the rules code is impossible to work with 4

5 How we deliver software Top-down Bottom-up Why do we do this? 5

6 Part 2: effective design and clean code

7 Only Flatten Prioritise Adapt of If we could deliver better focus on high-value features the cost of change anything, at any stage often, change often to feedback Learn! 7

8 Streaming Evolving Code Frequent Run What we would need requirements design we can change code integration all the regression tests often 8

9 Part 3: Getting there with BDD

10 A definition of BDD Behaviour-driven development is about implementing an application by describing it from the point of view of its stakeholders - Me :) 10

11 Second BDD is derivative generation agile methodology XP, especially TDD and CI Domain-Driven Design Acceptance Test-Driven Planning Neurolinguistic Programming (NLP) Systems Thinking 11

12 Getting Enough...agree What makes BDD? the words right is enough on Done Outside-in Interactions People over Process! 12

13 When Lewis Getting the words right I use a word, said Humpty Dumpty in a rather scornful tone, it means just what I want it to mean, neither more nor less Carroll - Through the Looking Glass 13

14 Model Create Determine...and...and...and Getting the words right your domain identify your core domain a shared language make it ubiquitous its bounded context think about what happens at the edges 14

15 Identify Do Then...and...because Enough up-front thinking the desired outcomes enough to feel safe to estimate keep a note of your assumptions blink estimate - with people you trust anything else is false confidence Estimation is fractal - don t misunderestimate! 15

16 A story is a unit of delivery Story 28 - View patient details As an Anaesthetist I want to view the Patient s surgical history So that I can choose the most suitable gas 16

17 Try to focus on the value Story 28 - View patient details In order to choose the most suitable gas an Anaesthetist wants to view the Patient s surgical history 17

18 Try to focus on the value Story 29 - Log patient details In order to choose the most suitable gas an Anaesthetist wants other Anaesthetists to log the Patient s surgery details for later retrieval 18

19 Agree on Done Define acceptance criteria as scenarios Scenario: existing patient with history Given we have a patient on file And the patient has had previous surgery When I request the Patient s history Then I should see all the previous treatments 19

20 Automate the scenarios Each step corresponds to running code Given we have a patient on file In Ruby: Given we have a patient on file = Patient.create end In we have a patient on file ) public void createpatient() { patient = patientfactory.create(); } 20

21 Also Start Implement Discover Repeat and Code-by-Example to implement known as TDD at the edges with what you know outermost objects and operations collaborators, working inwards mock them out for now until Done 21

22 Examples and...which Then bring it all together become code tests documentation Scenarios become acceptance tests become regression tests Automation is key 22

23 Map<int, Inside-out - an example Map<int, int>> portfoliosbytraderid; if (portfolioidsbytraderid.get(trader.getid()).containskey(portfolio.getid())) {...} Becomes: if (trader.canview(portfolio)) {...} 23

24 The The The The The The team stakeholders BAs QAs developers project manager 24

25 The destination

26 ...has...is...is...is...is Effective Design and Clean Code tangible stakeholder value delivered on time, incrementally easy to deploy and manage robust in production easy to understand and communicate BDD is a step in the right direction 26

27 Any Thank you questions?

28 Extreme Domain-Driven The The Bibliography Programming explained (2nd edition) - Kent Beck Design - Eric Evans Art of Systems Thinking and Way of NLP - Joseph O Connor 28