Osvaldo Grigo ir Vadim Platonov pranešimas "Kodas ir specifikacija: du zuikiai vienu šūviu" skaitytas Agile dienoje 2013 gegužės 9 d. Kaip Behavior-Driven Development idėjas pritaikėme kurdami finansinių paslaugų valdymo sistemą. Kaip galima kodą paversti pirminiu tiesos šaltiniu, kai automatizuotais testais užrašomi reikalavimai. Trumpai supažindinsime su mūsų architektūros specifika, paremta DDD, CQRS ir Event Sourcing principais, kurie atveria naujas galimybes, bet kartu atneša naujų iššūkių. Kokias darėme klaidas, ir kaip jų išvengti.

1. Kodas ir specifikacija
du zuikiai vienu šūviu
code spec
Osvaldas Grigas
Vadim Platonov

2. What happens next
● Motivation
● Case study
● Live demo

3. Specification?
Requirements?
Scenarios?
Docum
entation?
User stories?
What do we need?
Test cases?
Use cases?
Code?
amples?
Accepta

4. Start with the code?

5. Requirements?

6. Specifications?

7. Test Cases?

8. code
Specification
Requirements
Test Cases

9. What did we try?

10. Behavior-Driven
Development

11. BDD?

12. Domain experts + Devs
Specify scenarios in plain text
Devs
Automate scenarios as tests
Jenkins
Publish scenarios to Wiki
Domain experts
Describe features

13. Let's Make a Payment.

14. Domain experts
Describe a feature
Account can only be debited if
it has sufficient balance and is
not blocked for debit.

15. Domain experts + Devs
Specify 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

16. Devs
Automated 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) {
// ...
}
}

17. Room for
improvement

18. Developers
have to maintain stories, test code and their mapping
COOL

19. What if...
specifications were generated from test code?

20. Business language
● gets lost in implementation details
● is not enforced in code
COOL

21. What if...
core parts of production code were reflected
in specifications?

22. Specify
scenarios
in plain text
Automate
scenarios
as tests
Specify
scenarios
in code

23. 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?

24. code
Yes I can! *

25. 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");
}
}

26. DDD? CQRS?
Event
Sourcing?

27. Domain-Driven Design
Crash Course

28. DDD
Ubiquitous Language
Account
Debit
Credit
Asset
Liability
Balance

29. 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");
}
}

30. DDD
Entity
public class Account extends AggregateRoot {
private Balance balance;
public void credit(Amount amount) { ... }
public void debit(Amount amount) { ... }
}

31. 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");
}
}

32. DDD
Isolated Domain
Domain
data store
message
broker
client services

33. Event Sourcing Crash Course

34. Events
Capture all changes to domain state
public class AccountDebited {
public String accountNumber;
public BigDecimal amount;
public BigDecimal runningBalance;
public String currency;
}

35. Events
Never lose data
AccountCreated 0
AccountCredited 300
AccountCredited 1000
AccountCredited 1500
AccountDebited 900
AccountCredited 1200
AccountDebited 800
AccountDebited 700
time
Balance

36. 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");
}
}

37. Command-QueryResponsibilitySegregation
Crash
Course

38. Read Model
CQRS
Write Model
QueryCommand

39. CQRS
Command
public class DebitAccount {
public final String accountNumber;
public final BigDecimal amount;
public final String currency;
}

40. 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");
}
}

41. Putting it all together

42. MongoDB
Domain
(Aggregates)
Projectors
(Groovy)
Command
Handlers
Query
Services
Client
(Wicket)
Event StoreEvents
Events
Commands Projections
Projections
Events

43. Domain
(Aggregates)
Command
Handlers
User Story
Tests
Events
Commands
Mock
Event Store
Events
Events
Testing
the Domain

44. Live Demo
Coding Specifications

45. Attributions
Photo: Accidents - after crash 1978 Skoda
Author: Istvan Takacs
URL: http://commons.wikimedia.org/wiki/File:Accidents_-_after_crash_1978_Skoda.jpg
License: http://creativecommons.org/licenses/by-sa/3.0/deed.en
Photo: Tram in Kraków, Poland
Author: Astrorek
URL: http://commons.wikimedia.org/wiki/File:Tramwaj_krakow_3.jpg
License: 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 JBehave
URL: http://jbehave.org/
Image: Rainbow
@ Copyright Moonglowlilly
URL: http://moonglowlilly.deviantart.com/art/PNG-RAINBOW-324144428
Image: Debit card
URL: http://www.capitalistbanter.com/2011/05/featured/the-best-and-worst-time-to-use-a-debit-card/