Android test apps

version code

add a getVersionCode and getVersionName to app/build.gradle

Then build with ./gradlew assemble -PversionName=1.0.1 -PversionCode=2

flavors

add applicationIdSuffix for debug builds

add values/strings.xml with different application names per flavor/build type

dependency injection - dagger2

setup

• create class di/DefaultModule.kt
  • annotate with @Module
• create interface di/Injector.kt
  • annotate with @Component with modules set
  • annotate with @Singleton (needed if you create singletons in the modules)

build once. need dagger2 to generate DaggerInjector class

setup the injector in your Application's onCreate

di in view models

make the class inherit from (or a subclass of) AndroidViewModel. Get the injector from the application, and use that to setup the view model

networking - retrofit2 (with okhttp3 for logging)

build a custom okhttp3 client, and use that in the retrofit2 builder logging interceptor

add gson converter for json parsing

remember to add INTERNET permission

tests

Add custom class that extends androidx.test.runner.AndroidJUnitRunner, override newApplication and save the application to a field

Change the android.testInstrumentationRunner field to this class

in memory db

pass in the database into the persistence module. add a function (visible for testing, else private) in the application that builds given a passed-in persistence module.

in the tests, build an in-memory database. use this database to build a persistence module for the tests, passing this module into the application's dependency builder function in the onStart function

screenshots

use androidx.test.runner.screenshot.Screenshot.capture to get the screenshot details (which is enough to view the bitmap when debugging).

Then save it to a file, using a custom processor (to change the destination, else you might get permission errors)

Async tasks (ex network requests, db loading)

Add AsyncTaskTracker in production code, and track the start and completed events in (production) code

Inject a test specific implementation of this, which uses a counter to track the number of tasks that should still complete

Register this class as an idling resource, which causes espresso to wait for it to complete before continuing with assertions or actions.

general

change activity into activity+fragment

• inherit from Fragment
• move layout creation into onCreateView
• split other onCreate code into onActivityCreated
• add companion object to create new instance of fragment
• add layout for activity with just a FrameLayout
• add activity that sets up supportFragmentManager

events in live data

The problem: live data keeps old values, so observing on an already-setup live data will load the old values after the observer is setup

see https://medium.com/androiddevelopers/livedata-with-snackbar-navigation-and-other-events-the-singleliveevent-case-ac2622673150

Create a class (SingleHandledEvent) that holds the data to return. When the data is read the first time, return it, and also mark the event as "handled". On subsequent reads, return null

Add an observer extention to subscribe to these events, and fire a callback only when the data is read (see this comment on gist)

See SingleHandledListEvent for a list of data, all of which should be handled. This class allows adding more items to the list (in a new event in order to ensure it is read/updated correctly) while still only allowing it to be read/handled once. Useful when all items should be handled, and not just the last value (a periodic random number is used as example in the main fragment)