MSA, TBD, DDD, TDD, BDD, WTF?

1Copyright © 2019 Message4U Pty Ltd. All rights reserved.Copyright © 2019 Message4U Pty Ltd. All rights reserved. 1
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GeneralAssembly
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presentationandforregularCode
Mentoringmeetups.
Presentation
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presentation,proof-readingand
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Facilitation
Code Mentoring
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Copyright © 2019 Message4U Pty Ltd. All rights reserved.
Presenter:
Date:
2
MSA, TBD,DDD, TDD, BDD,WTF?
MicroserviceArchitecture,TrunkBasedDevelopment,DomainDriven
Design,TestDrivenDevelopmentandBehaviourDrivenDevelopment
MichaelLambert
June2019
Approved for Public Presentation

Thanks
VenueSponsor
GeneralAssembly
Providedthevenueforthis
presentationandforregularCode
Mentoringmeetups.
Presentation
MessageMedia
Providedthetimetopreparethis
presentation,proof-readingand
contentvalidation.
Facilitation
Code Mentoring
Providedaplatformforthis
presentation.
Slack:tiny.cc/melbcm

4Copyright © 2019 Message4U Pty Ltd. All rights reserved. MSA, TBD, DDD,TDD,BDD, WTF?
WhoisthisMichaelguy?
Welcome
• Senior PHP Developer @ MessageMedia
• Worked with Internet technologies since 1992
• Varied roles:
o Founderof an InternetAccessProviderin themid 90s
o Workedonthe tenderdocumentthat won AusRegistrymanagementrights for .AU
o PreviouslyLead Infrastructure(DevOps)Engineer
o Mentorat MelbourneCodeMentoringmeetup
• Fan of Agile processes and Symfony Framework
• Currentlyre-learning JS foruse in AWS Lambda
LinkedIn

AboutthisPresentation
Welcome
• Microservice Architecture
• TrunkBased Development
• Domain DrivenDesign and Development
• Test DrivenDevelopment
• Behaviour DrivenDevelopment
High-level overview of:
• Pub/sub &Queues
• CQRS
• Chaos Engineering
Brief mentions of:

Assumptions
Welcome
• Understanding of agile methodologies
• Knowing that “best practice” doesn’t always match corporate reality
• Desire to learn and improve
• Ability to apply concepts to yourskill-set
• Knowledge of git concepts suchas pull requests

Agenda
Microservice Architecture
TrunkBased Development
Domain DrivenDesign &
Development
Test DrivenDevelopment
Behaviour DrivenDevelopment
TyingIt Together
Q& A

Overview
• Breakinga product into small, self-contained services
• Removedependencies between services
• Reduce blast-radius (fewer services affected in case of fault)
• Simplified feature and team expansion
• Reduce technology lock-in
• Increasemaintainability
• Reduce onboarding time

Application
• Divide into logical components (services)
• Design standard communication interfaces (pub/sub and/or
queues)
• Avoid interdependencies
• Data is eventuallyconsistent
• Fault tolerant design
• Data-store per service

Agenda
Development
TyingIt Together
Q& A

Overview
Trunk BasedDevelopment
• Enabler of continuousintegration and continuousdelivery [ordeployment]
• Multiple commits to master per developer per day
• Branchby abstraction (feature flags)
• All commits (or at least PRs) must pass testing
• Fixforward strategy
• Scales to large team sizes
• Avoids mergeconflicts

Styles
Pure Trunk Based Development
• All commits to master
• Code-pairing
• Automatic rollbacks
• Small (or tiny) teams
Short Lived Features
• Feature branches last less than 1business day
• Strong code review process
• Anyteam size

Requirements
• Excellent review capabilities and/or code pairing
• Automated build and test services (CIpipeline)
• Feature flags
• Small tasks
• Automated rollback or strong fix-forward capability
• Developer commitment

ShortLived FeatureBranchesProcess/ Pull-requestWorkflow
• Createa feature flag infirst commit
• Implementthe feature insmall steps
• A feature branchshould be mergedwithin one day
• Squash commits when merging
• Every mergemust bereviewed
• Master can be released at anytime

Agenda
Development
TyingIt Together
Q& A

Overview
DomainDriven Design & Development
• Bound to a business model
• Language specific to the business domain
• Reduces support time
• Requires translation between services
• Functionality driven by business need

Implementation
DomainDriven Design & Development
• Understand thebusiness domain beforeplanning
• Planningmust be domain-centric
• Useterminology dictated by thebusiness function
o Accountswouldhave“debtors”and“creditors”
o Warehousewouldhave“recipients”and”senders”
o Managementwouldhave“customers”and “suppliers”
• Inter-servicecommunication requirestranslator functionality

Agenda
TyingIt Together
Q& A
Development

Overview
TestDriven Development
• Tests written beforefunctionality
• CanincludeBDD (covered next)
• Often interpreted as just unit tests
• Find errors early
• Test for failure
• Refactor with confidence
• Mock external services

Unit Tests
• Write tests for eachfunction before writing the function
• Test both good and bad paths
o Is the expected value returned?
o Did the correctexception get thrown?
• Ensureall tests pass
• Only test thelocal code

Implementationand ProcedureEnforcement
• TrueTDD can be hardto adopt
• 100%code coverage is not always viable
• At a minimum,tests must bewritten before commit
• Requiresclear functionalitydefinition
• Automated test runnershelp enforce testing
• It’s nevertoo late to start; monitor coverage for
constant improvement
• Does not replacefunctional and manualtesting

Agenda
TyingIt Together
Q& A
Development

Overview
Behaviour Driven Development
• Clearacceptance criteria (as user stories)
• Acceptance criteria canbe usedas functional tests
• Tests real world use cases
• Support issues arereplicated and a failing test written
• Test often written by domain experts
• Does not replaceunittests ormanual verification testing

FunctionalTestsand AcceptanceCriteria
• Acceptancecriteria should be written as user stories
o GIVENx, WHEN y, THEN z
o GIVENI have a user account
WHEN Ientermyusernameand password
THEN Iwill belogged in
• Acceptancecriteria define functional tests
• Should bewritten by domain experts, product owners and QA

Implementationand Integrationwith Unit Tests
• Test runningshould beautomated
• Functional tests can be runin parallel to unit tests (reduce time to deploy)
• Functional tests should onlymock3rd party services
• Does not relyon unit tests
• Does not replace unittests

Agenda
TyingIt Together
Q& A
Development

ServiceDefinitionand Planning
TyingitTogether
• Divide by business domain (DDD) and service (MSA)
• Ensuredesign does not relyon other services (MSA)
• Useterminology local to the domain (DDD)
• Write high-level functional tests (BDD)

CQRS (CommandQuery ResponsibilitySegregation)
TyingitTogether
• MSA and DDDwell suited to CQRS
• Best incomplex business models
• Read and write services are separated (mayshare a datastore)
• Out of Scope: When to use CRUDand when to use CQRS

IssueDefinitionandPlanning
TyingitTogether
1. Define user stories
2. Break down to individual stories
3. Convert userstory to acceptance criteria
4. Convert acceptance criteria to functionaltests
5. Verifyfunctional tests cover user stories
• Small Tasks (less than one day of work)
• Testable
• User-centric
• Design for failure

Coding
TyingitTogether
• Usedomain based terminology
• Do NOTrelyon other systems
• Codemust behumanreadable
• All code must be testable and tested
• Scope creep is not allowed (create a new task)
• One task per issue
• Understand the issue before coding

AutomatedTestingandDeployments
TyingitTogether
• Test before everycommit (ideally)
• Test everyPR before merge(required)
• Automate unitand functional tests
• Implementproduction testing
• Consider chaos engineering
• When code quality is high enough, implement continuous deployments

Agenda
TyingIt Together
Q& A
Development

messagemedia.com
Let’s stay in touch
Thankyou
michael.lambert@messagemedia.com.au
LinkedInQR Code

Australia | New Zealand | United States | United Kingdom
1800 155 228
messagemedia.com

MSA, TBD, DDD, TDD, BDD, WTF?

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