Kodas ir specifikacija: du zuikiai vienu šūviu

Kodas ir specifikacija

du zuikiai vienu šūviu

code spec

Osvaldas GrigasVadim Platonov

What happens next

● Motivation● Case study● Live demo

Specification?

Requirements?

Scenarios?

Documentatio

n?

User stories?

What do we need?

Test cases?

Use cases?

Code?

Examples?Acceptance criteria?

Start with the code?

Requirements?

Specifications?

Test Cases?

code

Specification

Requirements

Test Cases

What did we try?

Behavior-Driven Development

BDD?

Domain experts + DevsSpecify scenarios in plain text

DevsAutomate scenarios as tests

JenkinsPublish scenarios to Wiki

Domain expertsDescribe features

Let's Make a Payment.

Domain expertsDescribe a feature

Account can only be debited if it has sufficient balance and is not blocked for debit.

Domain experts + DevsSpecify scenarios

Scenario: Debiting an account with sufficient balance

Given a liability account LT000001 with a balance of 100 USD,

not blocked for debit

When the account LT000001 is debited for 20 USD

Then the debit succeeds producing a running balance of 80 USD

DevsAutomated scenarios as tests

public class DebitAccount extends JUnitStory {

@Given("a $type account $number with a balance of $balance USD, $debitStatus for debit") public void givenAnAccount(String type, String number, int balance, String debitStatus) { // ... }

@When("the account $number is debited for $amount USD") public void whenAccountIsDebitedBy(String number, int amount) { // ... }

@Then("the debit $result producing a running balance of $balance USD") public void thenDebitResultsIn(String result, int balance) { // ... }}

Room for improvement

Developers

have to maintain stories, test code and their mapping

COOL

What if...

specifications were generated from test code?

Business language

● gets lost in implementation details

● is not enforced in code

COOL

What if...

core parts of production code were reflected

in specifications?

Specifyscenarios

in plain text

Automatescenariosas tests

Specifyscenarios

in code

Story: Debiting an account

Scenario: Sufficient balance

Given: Account with

● id: LT000001● balance: USD 100● balance type: Liability● additional currency support: Disallowed● debiting allowed: Yes● crediting allowed: Yes

When: Debit account with

● account number: LT000001● amount: 20● currency: USD

Then: Account debited

● with amount 20● with running balance 80● with currency "USD"

code

Can I do that?

code

Yes I can! *

public class Debiting_an_account extends Story<Account, DebitAccount> {

@Test public void sufficient_balance() { givenEvents( new AccountCreated("LT000001", "USD", LIABILITY), accountCredited("LT000001", "any", $(30, "USD")), accountCredited("LT000001", "any", $(70, "USD")));

onCommand(new DebitAccount("LT000001", "any", $(20), "USD"));

expectEvent(AccountDebited.class) .with("amount", $(20)) .with("runningBalance", $(80)) .with("currency", "USD"); }

}

DDD? CQRS?Event

Sourcing?

Domain-Driven DesignCrash Course

DDD

Ubiquitous Language

Account

Debit

CreditAsset

Liability

Balance





}

DDD

Entity

public class Account extends AggregateRoot {

private Balance balance;

public void credit(Amount amount) { ... }

public void debit(Amount amount) { ... }

}





}

DDD

Isolated Domain

Domain

data storemessage

broker

client services

Event Sourcing Crash Course

Events

Capture all changes to domain state

public class AccountDebited {

public String accountNumber;

public BigDecimal amount;

public BigDecimal runningBalance;

public String currency;

}

Events

Never lose data

AccountCreated 0

AccountCredited 300

AccountCredited 1000


AccountDebited 900


AccountDebited 800

AccountDebited 700

time

Balance





}

Command-QueryResponsibilitySegregation

Crash

Course

Read Model

CQRS

Write Model

QueryCommand

CQRS

Command

public class DebitAccount {

public final String accountNumber;

public final BigDecimal amount;

public final String currency;

}





}

Putting it all together

MongoDBDomain

(Aggregates)

Projectors (Groovy)

Command Handlers

Query Services

Client (Wicket)

Event StoreEvents

Events

Commands Projections

Projections

Events

Domain (Aggregates)

Command Handlers

User Story Tests

Events

Commands

MockEvent Store

Events

Events

Testingthe Domain

Live DemoCoding Specifications

Attributions

Photo: Accidents - after crash 1978 SkodaAuthor: Istvan TakacsURL: http://commons.wikimedia.org/wiki/File:Accidents_-_after_crash_1978_Skoda.jpgLicense: http://creativecommons.org/licenses/by-sa/3.0/deed.en

Photo: Tram in Kraków, PolandAuthor: AstrorekURL: http://commons.wikimedia.org/wiki/File:Tramwaj_krakow_3.jpgLicense: http://creativecommons.org/licenses/by-sa/3.0/deed.en

Photo: Mokate 3in1© Copyright 2013 Mokate S.A.URL: http://www.mokate.eu/

Image: JBehave examples@ Copyright JBehaveURL: http://jbehave.org/

Image: Rainbow@ Copyright MoonglowlillyURL: http://moonglowlilly.deviantart.com/art/PNG-RAINBOW-324144428

Image: Debit cardURL: http://www.capitalistbanter.com/2011/05/featured/the-best-and-worst-time-to-use-a-debit-card/

http://jbehave.org/

http://moonglowlilly.deviantart.com/art/PNG-RAINBOW-324144428

http://www.capitalistbanter.com/2011/05/featured/the-best-and-worst-time-to-use-a-debit-card/

Technology

Kodas ir specifikacija: du zuikiai vienu šūviu