Wann soll ich mocken? XP Days Germany David Völkel

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1 Wann soll ich mocken? XP Days Germany David Völkel

2 @davidvoelkel TDD & Design

3 SCHICHTEN TESTEN?

4 INTEGRIERTER TEST

5 Unittest MOCKING Mock

8 TRADE-OFF ZU GROSS vs ZU KLEIN aufwendiges Setup Fehlerfindung # Testfällen Langsames Feedback Refactorability sinkt Isolationsaufwand Zu wenig Nutzen Lesbarkeit

9 Woran orientieren?

10 IDEOLOGIEN MOCKISTS CLASSICISTS "Mocks Aren't Stubs", Martin Fowler

11 TRADE-OFFS statt IDEOLOGIEN!

12 USE CASES Anbindung Drittsysteme MOCKISTS CLASSICISTS

13 USE CASES Bedingte Interaktionen Anbindung Drittsysteme MOCKISTS CLASSICISTS

14 USE CASES Bedingte Interaktionen SWEETSPOT Anbindung Drittsysteme MOCKISTS CLASSICISTS

15 USE CASES Geringer Nutzen Bedingte Interaktionen SWEETSPOT Anbindung Drittsysteme MOCKISTS CLASSICISTS

16 USE CASES Geringer Nutzen Bedingte Interaktionen VERMEIDEN SWEETSPOT Anbindung Drittsysteme MOCKISTS CLASSICISTS

17 MOCKING VERMEIDEN SWEETSPOT BEST PRACTICES

18 VERMEIDEN

19 DONT MOCK VALUES!

20 DON T MOCK VALUES! new Value()

21 DON T MOCK VALUES! new Value() TestDataBuilderForValue.withDefaults().withField( 1 )

22 INTEGRATION OPERATION SEGREGATION PRINCIPLE "Integration Operation Segregation Principle", Ralf Westphal "Die kniffligen Fälle beim Testen - Sichtbarkeit", Stefan Lieser

23 INTEGRATION OPERATION SEGREGATION PRINCIPLE public void sendmailingto(string ) { Customer customer = customerdb.findcustomerby( ); String title = customer.getsex() == Sex.MALE? "Mr" : customer.getmaritialstatus() == MaritialStatus.MARRIED? "Mrs" : "Ms"; String content = "Hello " + title + ". " + customer.getname() + ",\n\n" + "We have a special offer for you.\n\n" + "Best regards,\n" + "ACME Customer Service"; mailservice.sendmail( , content);

26 INTEGRATION OPERATION SEGREGATION PRINCIPLE public void sendmailingto(string ) { Customer customer = customerdb.findcustomerby( ); String content = rendercontent(customer); mailservice.sendmail( , content); private String rendercontent(customer customer) { String title = customer.getsex() == Sex.MALE? "Mr" : customer.getmaritialstatus() == MaritialStatus.MARRIED? "Mrs" : "Ms"; return "Hello " + title + ". " + customer.getname() + ",\n\n" + "We have a special offer for you.\n\n" + "Best regards,\n" + "ACME Customer Service";

27 TESTS? public void sendmailingto(string ) { Customer customer = customerdb.findcustomerby( ); String content = rendercontent(customer); mailservice.sendmail( , content); private String rendercontent(customer customer) { String title = customer.getsex() == Sex.MALE? "Mr" : customer.getmaritialstatus() == MaritialStatus.MARRIED? "Mrs" : "Ms"; return "Hello " + title + ". " + customer.getname() + ",\n\n" + "We have a special offer for you.\n\n" + "Best regards,\n" + "ACME Customer Service"; N Unittests

28 TESTS? public void sendmailingto(string ) { Customer customer = customerdb.findcustomerby( ); String content = rendercontent(customer); mailservice.sendmail( , content); 1 Integrierter Test private String rendercontent(customer customer) { String title = customer.getsex() == Sex.MALE? "Mr" : customer.getmaritialstatus() == MaritialStatus.MARRIED? "Mrs" : "Ms"; return "Hello " + title + ". " + customer.getname() + ",\n\n" + "We have a special offer for you.\n\n" + "Best regards,\n" + "ACME Customer Service"; N Unittests

29 PUSH LOGIC DOWN THE STACK Siehe "The Failures of Intro to TDD " - Justin Searls

30 PUSH LOGIC DOWN THE STACK

31 SWEETSPOT

32 BEDINGTE INTERAKTION public String signup(string username) throws Exception { if(userdb.finduserby(username) == null) { userdb.createuser(new User(username)); return "Welcome " + username; else { return "Username ' " + username + "' " + "already taken, please choose another";

33 SYSTEM GRENZEN Adapter 3rd Party Service

34 SYSTEM GRENZEN Mock 3rd Party Service

35 OUTSIDE-IN DESIGN

36 OUTSIDE-IN DESIGN Alternative Fake it

37 BEST PRACTICES

38 NO OVERSPECIFICATION!

39 NO OVERSPECIFICATION! Specify exactly what should happen but no more

40 REIHENFOLGE?

41 COMMAND & QUERY SEPARATION REIHENFOLGE userdb.createuser(new User(username)); public String signup(string username) throws Exception { if(userdb.finduserby(username) == null) {... else {... IMMER NÖOTWENDIG?

44 COMMAND & public SEPARATION void signup() throws Exception {... when(userdb.finduserby(anystring())).thenreturn(null); mailingservice.signup(username); verify(userdb).createuser(new User(username)); REIHENFOLGE userdb.createuser(new User(username)); public String signup(string username) throws Exception { if(userdb.finduserby(username) == null) {... else {... IMMER NÖOTWENDIG?

47 COMMAND & public SEPARATION void signup() throws Exception {... when(userdb.finduserby(anystring())).thenreturn(null); mailingservice.signup(username); verify(userdb).createuser(new User(username)); public String REIHENFOLGE signup(string username) throws Exception { if(userdb.finduserby(username) == null) {... IMMER NÖOTWENDIG? userdb.createuser(new User(username)); Allow Queries, expect Commands!

48 LISTEN TO YOUR TESTS! Image by M.J. Moneymaker

49 LISTEN TO YOUR TESTS! # Verifications Image by M.J. Moneymaker

50 LISTEN TO YOUR TESTS! # Verifications Overspecification! Image by M.J. Moneymaker

51 LISTEN TO YOUR TESTS! # Verifications Overspecification! # Dependencies Image by M.J. Moneymaker

52 LISTEN TO YOUR TESTS! # Verifications Overspecification! # Dependencies Extract Class! Image by M.J. Moneymaker

53 LISTEN TO YOUR TESTS! # Verifications Overspecification! # Dependencies Extract Class! # Interactions Image by M.J. Moneymaker

54 LISTEN TO YOUR TESTS! # Verifications Overspecification! # Dependencies Extract Class! # Interactions Tell, don t ask! Image by M.J. Moneymaker

55 TELL DONT ASK public void volumeupclicked() { int volume = speaker.getvolume(); if (volume < speaker.getmaximumvolume()) { speaker.setvolume(volume++); => Tell don't ask

56 TELL DONT ASK public void volumeupclicked() { int volume = speaker.getvolume(); if (volume < speaker.getmaximumvolume()) { speaker.setvolume(volume++); => Tell don't ask

57 TELL DONT ASK public void volumeupclicked() { int volume = speaker.getvolume(); if (volume < speaker.getmaximumvolume()) { speaker.setvolume(volume++); public void volumeupclicked() { speaker.putupvolume(); => Tell don't ask class Speaker { public void putupvolume() { if (this.volume < this.maximum this.volume++;...

58 VERMEIDEN

59 SWEETSPOT

60 BEST PRACTICES

61 MOCKIST ODER CLASSICIST?

62 MOCKIST ODER CLASSICIST? TRADE-OFFS!

63 QUELLEN Growing Object Oriented Systems, Nat Pryce, Steve Freeman "Mocks Aren't Stubs", Martin Fowler "Integration Operation Segregation Principle", Ralf Westphal "Die kniffligen Fälle beim Testen - Sichtbarkeit", Stefan Lieser

64 Q&A?!

65 Licence Creative Commons Attribution-ShareAlike 3.0