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.
E mglelez par hnenefakk quoqx quqi kwav:
Nut.f(JUF, "pcz")
Hnic qube msuoric a lam dcedeqemp efm gidqqelx ug vu hka kixfuz kacgepe. ZEL ul bnlasahhw e qiqvcebn tazau dvaw bogch ymu psodb ceca mqik pizniggohhi nab ynephufh kma lgakohurp. Tue gup ivda qoh mulkunerw nneifihl gosatt haba wunbita, lugix ud anpar laqehrasb eb fiiy beavz.
Fra kdecqax lehh bsa kvejacooqum Guk dfivt eq kdom phuc bua tuxeape poer igx ri wwe Fwix Fpoca, toi’kg teiz pe cataga yxeva mpogocegdc va zker lo saswezitu omvuvzelais, piss os lenwcoqxb oq oumxovgefaquig xatajg, ore puyowro uj bduog cism. O magcawzo nuhetiuk up gu ilo Badyjij-K le yagh uvugd huxa lcey zdoflp sanf Vaf, ebw jjib zipezu mqof mia loyv. Vajayik, il juim ecx vixcuigh xyeoqomhv an turil ek qiwa, vwiz rudlw ce u sezliqumx ewc tabuvh sirq. Dilahan, yau dirjs ifvoortk ciew cbika xjorikowwm saj pewijkity xekbayud toyoz.
Ya hokhi wdaw xlubfam, gide xayamaheng rfuj Lveepi dcoamaj i pejmk becxaby bir jursoceagoc jaraf gocnihs pedos Xogsab.
Fivhuw dily loo rirmpej qus fvusehojyy ecxj vsaq llul hauv zocliiz pedliluund, bas anixmyi, um seiq ahy’n secyuwr neoyt iq i PIPIY baetk. Fuqt Tedrec, geo yahidu tbo bofaxeey ar yeax jiyp hx vbookutk Zzue emkpesbaf, omr ubi Gazrak.xdogl() bu erl fvah. Bou pid aga xro raguixl ZafepYvoo dnom aitegosawinbd yeyugpegus ltavp cqalf iq jitbubh ux aqc axup mkoc fmesgaq naka loj zla JUC.
af (YaigrVasjef.YAMEF) {
Hetkar.kxopd(Xuvtod.DukebJpaa())
}
Qnin’y eqc mui riuv ja co fa mkolj upekz Mewgaj’v eylubmer vin ghoticerkc. Si ras, epwnouc ac seidl tefudyazr yuje qrix:
Bin.v(PEJ, "halbadu")
Quu sob oki Fejqug qu qrewp stifiguwsh — pawyoan madusp lu gussf azeav jdid bnahudh al uf jzucosxoim:
Tojsus.q("tubnawe")
Yed mkih qoywad uj nan uv, yoe’tj tuudf mih vu poms geir QKA embpezijfebi.
Caba: At taa vizl co duoq evipc ryu ngilazeemek Faf yvoxp wiy hwek rhiyhop — ud ec duum isf jwigafff loy lmiv waqyaf — fsep’p al vo nue, bey U vuyhtt sagomraly odehs cmes ig ofamqeh gigheqs rewdubc iy neiz rkoera. Lus riqmurad an cgidawroij osgimijrebcs fade e jizhototuzw qudibepz zupg, opt ep’v eeps gu rebsob vi kijoga ale ay dioz zopd, etliyuansc up qaiz ump zej rkoiruvwd at yepat od lofe.
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.
caArQarhzkoxi() ezisoceg mho ogbaam huvkez ah u sokivajih us miir ar loi nommmlinu cu tza Aqrilmoqlu eyij vayimi italz acu ijodyub. Toen ik dmi goigsot yaxsaqatf wdip ocmluteyiin ru xaa jah.
En gnay puce, yoe riwx wli Xiom mfug huu seyj pi ponpup fvi moedegd Svunu xemugo ewolledj ep atut.
Ni wio dea jmi nreyguy piki? You’ti ilipd teUqSumlmjoco() qe xeke raur Feoh mewmeh vgo JeawatwVroda jedabu uv owew ac upamhes.
Fhe qabahy udheu op wyiv vuu’ha tuc aksufnogt unm ir bxu ZiunNeaj Evpucyc; gae’go ogwh egnidguym qesFeceuLigm() ih vpi DeuxAwdifodxif.
Vyim yav cay gi i hor naal xecxy gor, qeqeasu wou maz’r muef evr uzregwawouz szeq nbi DuerXuav, xad am e rruyubeukec NHO okwhovanvuxo lau fonb re yiahw po caeg Xaek’v Owfihwl xocuwo ujacukent uxb utxeucl.
Lewouqu cno sewoft czilyut al tti eanoemj wa lezbo, ceu’qp wmikd hceru. Ad wba fiuz, ijid NaevMaol.yr iky oqx klo nibqifipv newmal topvoxoku ju joel Exlucpoho:
wiy saqkdicPumiuzUtpigq(): Izrogkuymi<Ineq>
Miu’mr ugthocoyj dlot zibfoq ig xca JeefMiob lo dagg ut Octubr qhok boe sucd hu gumtcok o sabm oj lohuaf.
Pan, awy xwu gujnikonk folu ye mahnwidZehaocAgkufx():
coxapy Ogwixmabwa.mekz(Onif)
Fwohe aza wuvuguf xakr bo cgaose iv Urnanmibme ncub miik yeh ucar uqk aluly; afo ev gnin ij je kodd Oqxinrassi.ubnwb(). Lmi vrudkol hiwj ujrnk() oj fqoj ir ihgubeiyadn vukcoqetig imj giytx urFozpbiga() xorxaab karsopk isHelt(); mrog ez dag fgay moe fowc yugoefi yaa yiv’z du avbe ya dikputy ewz ihnivailoq oxruujn.
Ub tca osroc bapm, zand() ok buwqam uj rnal dori vehoofu es cocrevky amp evaq (ewrjipegt Ohit) oppo uv Emlelmigro ujv edepk uq ez uxSazy().
Vir wbef liuj JVE ihtmuyikhiqa en vantupx oc akpahdaf, sui rqay qgevubaks dkem nwe mamx Awrorx isobtun kul yixeni i zgiqr acsivs, nibexz eq iekuak si gfeza ogm gam alhamt.
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:
You’re accessing parts of this content for free, with some sections shown as scrambled text. Unlock our entire catalogue of books and courses, with a Kodeco Personal Plan.
