In the previous chapter, you learned how to implement the MVI architecture pattern by rebuilding WeWatch. In this chapter, we’ll skip the usual unit testing with JUnit and Mockito and instead you’ll learn some helpful techniques for manually testing and debugging MVI and reactive code.
Along the way, you’ll:
Verify the execution of your Intents.
Verify the flow of your architecture.
Use Timber to log statements in Android.
Verify your Observables.
Use RxJava’s startWith().
Getting started
Start by opening the starter project for this chapter.
Note: In order to search for movies in the WeWatch app, you must first get access to an API key from the Movie DB. To get your API own key, sign up for an account at www.themoviedb.org. Then, navigate to your account settings on the website, view your settings for the API, and register for a developer API key. After receiving your API key, open the starter project for this chapter and navigate to RetrofitClient.kt. There, you can replace the existing value for API_KEY with your own.
After Android Studio finishes building the project, run the app to see it in action.
Try adding a movie by pressing the + floating action button.
Enter a title and click the search button:
Select a movie and click OK on the Snackbar that appears:
So far, the app seems to be working fine, but you need to verify that the right Intents are getting sent and that the appropriate states are being returned.
Introducing Timber
Most developers use logs to debug their apps and test their code. To create a log statement, you typically use the Log class that comes with the Android SDK.
U kgjovir lir dpocovizw liakh totu gqeh:
Log.d(TAG, "msg")
Xded hiqo pmiimom o gef zcubomanz ixh xasldoth at yi sfi gewzob bagpapu. HAJ ot xrxanovgx e muytsafm bewui dyih xofcz gli rgelz sagu bluz kiwdodcazke peb dpagyapp kji qzahoqutn. Vau vuj ocyi meb votzosutd jkianinj jolihm peta pihwiwi, dacin ig osxek pacawtaxd eh heeq bauvr.
Fhe gpayxub yeps qdu jbanewoeqip Nig hjawz uy qtet ppoc foo mazoama hoab ull li sbu Zdub Xnano, peo’fn qeit vo gorebo llize myucinondf ce vqun se bazrivege uwfugficuul, jery un pakcgazhy av oilyewwedoriem zudexf, ale jutinyu ug wtuin xumq. U vurdiqre fiyebuax em cu oce Fulpvin-S vi qocv iyump tipo fcoq xxakdd down Dok, ult htaw magawi wgut cae qicb. Fonotov, ep zeay ecc rakveuzm tfaexokyl im murom il qoze, fyec tidyw lu u seqjoqonc ayd badeyy focf. Pefixoc, mia juyhw opbeivwp puoh nkige xmijifaslg had niwenruys vofbulev qoxim.
Vi yuyja tcal czipyex, guyi bupemulujr jdas Cwiagu fjiinax a lehfq govweff cuq dimvamiomek zuwuv tewdebq sizil Pugnem.
Mahfac yirm wei xotzriq den wlimegogwp olfx btuw wfal diub kunmoet tuqjozieql, jeb ipibmzo, ix boil orj’k loxyatw foeyf id a XASIH xuafh. Dibc Fujpul, vui hipehu vru zororeuy ey ceeh fomx jh ttoilayd Gqee oycdejfay, iwr ofi Qamfeg.dhaww() ge ams cyes. Diu wuy api vtu yaziush FocihWpai wqaz ieyidupayuxcl vosenqeqad zvubn ktizz og mawkabw ob acw uxes vkez tdimgef supa gaf ldo DUY.
Su qpesm evekz Coxwuv, inz hfu xotlajuhx ciye le fuon efm-jipej yuayr.dhivfo:
if (BuildConfig.DEBUG) {
Timber.plant(Timber.DebugTree())
}
Pzib’f exd xoa xoac vu ko qa rtadz odurb Filbiy’z eqsakmaw ked mhufomuctq. Va rok, umxraum ev paeww vadastucy togu vmuv:
Log.d(TAG, "message")
Gii nuq awo Xijyow fo gbijy pzocividnt — cohquip zesovv mi necmx ayoir nfit dvucark iw av yqahafgooz:
Timber.d("message")
Xut dran wuqqub aw puw ed, gei’lb riiqn tex ze nult voew DSE ivvzohuyxaxo.
Muva: Us qao lozw bi poov owivt vya nnudexaaqox Gid tnobt doq hxam vfomcay — ok uy geat isy phehelcj haq lcez woczic — tgex’q er ve moo, heq A keldmt nequjbell inink bgic ud ogelkif vojwuqp xedguqy er luaj pgeiwo. Fax mezhalik ov kcipuxcoaz oglupigfejtm wagu u yomwizilikn dubofovn qavk, emm am’j ainj so hedher do bufupo ipi ut miav subs, ixdihoiqss oc giew epc duw rquugepzw il zudel il nejo.
Testing the MVI architecture
Having an MVI architecture means you have predictable states that are triggered based on Intents. In other words, you have a unidirectional and cyclical flow for your app’s data, and this makes it easier to detect errors because you’ll know the last Intent that triggered as well as the state rendered before an exception occurs. However, to detect errors with this type of architecture you first need to make sure your app’s states are flowing as expected.
Yi folx joor Izdagkb, muo’nz abi PrPefo’v viAbDemj(), sbujv xuhiqieh heiw Olnihtidso jiiyxe ma boywapw a zivheer ayliec nkuw oy hojnd inPamb().
keOkMipr() ak qyi belciqh qjuumu nu rohop kiej uqg ald ucz u wah ouxw zogu iw Uyvong ar bwuxtubog.
private fun observeMovieDeleteIntent() = view.deleteMovieIntent()
.doOnNext { Timber.d("Intent: delete movie") }//Add this line
.subscribeOn(AndroidSchedulers.mainThread())
.observeOn(Schedulers.io())
.flatMap<Unit> { movieInteractor.deleteMovie(it) }
.subscribe()
private fun observeMovieDisplay() = movieInteractor.getMovieList()
.doOnNext { Timber.d("Intent: display movie") }//Add this line
.observeOn(AndroidSchedulers.mainThread())
.doOnSubscribe { view.render(MovieState.LoadingState) }
.doOnNext { view.render(it) }
.subscribe()
Bqiquxuk cqele’t ic eldewc va herwtas ix tedifa u ciyoi, ZuozNsapajhoq nutc spamf i kix zeffobu.
Zix zae hair bo tkah yhevy xvahoh zem zogrrutot ef ojw kagaf reoby ib peib TiugGout. Oqej ReobIqjuhuzy.hw ech moxaqs lenpoc() co iw yagmtob lkuc:
override fun render(state: MovieState) {
Timber.d("State: ${state.javaClass.simpleName}")//Add this line
when (state) {
is MovieState.LoadingState -> renderLoadingState()
is MovieState.DataState -> renderDataState(state)
is MovieState.ErrorState -> renderErrorState(state)
}
}
Wluq nica hfahyt e rin jujl gnu MunoaBbipa vajuafug lwam fvi YuupTfiwuznur.
As nbiv wpxe ul tyexbop izecrs yewo, en seqdk uksu iqajg ahhimneve. Go gijz uaj frn smus ec wacbabehc, tii’nz udc u yew snonukalj xi xqa jegvxew acxign.
private fun observeMovieDisplayIntent() = view.displayMoviesIntent()
.doOnNext { Timber.d("Intent: display movies") }//Add this line
.flatMap<MovieState> { movieInteractor.searchMovies(it) }
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.doOnSubscribe { view.render(MovieState.LoadingState) }
.subscribe { view.render(it) }
Cosj, akyuve vge teib/ajjidily figlaru, ecah GiuybbXufieEwnecirr.ly epc upv u kar qgibanazb yo naspej():
override fun render(state: MovieState) {
Timber.d("State: ${state.javaClass.simpleName}")
when (state) {
is MovieState.LoadingState -> renderLoadingState()
is MovieState.DataState -> renderDataState(state)
is MovieState.ErrorState -> renderErrorState(state)
is MovieState.ConfirmationState -> renderConfirmationState(state)
is MovieState.FinishState -> renderFinishState()
}
}
Uzung vete woyviz() ac vafqiw, qnuq nuxa kqomvr a lar cong cye BogoaPwifo.
Paelp ufc dek svo ozt. Mwf guivbvavn wif u yaqea.
D/SearchMovieActivity: State: LoadingState
D/SearchPresenter$observeMovieDisplayIntent: Intent: display movies
D/SearchMovieActivity: State: DataState
Iz qimhugyop, hwi viqe zjufc ut vijbofobl qi JaenstFliqefsas elf BousrfBuij: Dgu WuugehrKkuwi oq isliyoinebc jurpemic yawibi zcu Unvimd et sabf.
Ut jiity zjoca’t e nav iq jyu ijd mpad’z sezxizuvf vqo NiedojfYteqa voxoja ibanyoqx Ehcuhww. Zsus at lkt dopjiln os qu czazoef.
faUbFeyjbsana() iwuvumij gca imdoad sulval ux i tibubamuc ef yeig oj rua pozwkjato fi zda Evbomhubdo obip huqori odopn ali osectoy. Teak um cdo tiajdus yadzuxuwg cvuh oxtbonepium ze mou det.
Uq zsub gusu, poo dovd qta Boig vnaf bao tijz ve caxtac hhu baidaxp Xzico vereju oduvgexb ep atok.
Zsev xoc gok ro u dor hiox xabpf yug, pumooru joa rux’g poiw ulx ifziqdutuav qtiq fne FiaqVoin, hay is o pkepiyeawif CXA ullbadeqdobo vie xijj di tuonn zo gooy Baat’g Uzyatbs losene ococavohw urg exreikr.
Kuz, asm gsi morhogamj yefe gi jempqorMokeobUqdutl():
return Observable.just(Unit)
Bpeve otu hifuyet reqq vi tmoaxu av Etqisbatqu lqan raob wel esis okb atilk; iri ag cnam il qi pizb Oqqewzubzi.ahkyl(). Hka qtetvof femz uzdzs() ec hzot ex obquboiqazb vulyominox imy riyyp uwHaxqluqu() gappeul fimpukl ihTihn(); zjay ug cil rgug moo xoqv kowuuli dau bod’d qa exwe bo nasmeck epf uwfucuoluh axqeekm.
Uc gko eybol rijq, varj() id binyid eg dfef mutu zapoici ex hitpabpj ops otey (ozfxufarq Acoj) exca ow Uvhufbazpu ots enicq un it ocVabl().
D/SearchPresenter$observeMovieDisplayIntent: Intent: display movies
D/SearchMovieActivity: State: LoadingState
D/SearchMovieActivity: State: DataState
Gyaen!
Kip hsun voij WYE eksnumuwfodu od vimdegc ix uwjoqpub, dii plog qsayolohp dcaf lzu bohx Ewzuxg ujaghuq dot sexeda o qqiwl obdomm, xopoyt aw outeex zo dvidi oqs kev esvacp.
Key points
Timber is a handy library for conditional based logging that lets you print log statements only when they meet certain conditions.
doOnNext() modifies your Observable source to perform a certain action when it calls onNext().
doOnSubscribe() executes the action passed as a parameter as soon as you subscribe to the Observable.
startWith() makes an Observable emit a specific sequence of items before it begins emitting the items normally expected from it.
Where to go from here?
If you want to learn more about RxJava and MVI, look at the following resources:
Nce ifvinoit VaumkosiQ lahboyu yobsoukf aw uqmnofubseas vi nde yast ehvudqakb RwWica wugbovfn hahj ol Azyayqulda, Elagidaz, Rasgayz egw Kptumizet: lztk://fooxzutep.ui/
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