Testing a minimized build

About minimization: link

We want to run UI tests against build as close as possible to a production one.
It's quite a challenging task, mostly because of tooling problems: #126429384.
Developers should maintain a list of keep rules of code referenced from a test app manually.

We work around these problems by using keeper.

Build type

Android Gradle plugin uses testBuildType property to determine which build type to test.

We chose stagingAutoTest as a type to test against in CI environment.
However local builds defaults to debug type for faster test writing cycle.

Developer who wants to reproduce test problem specific to CI locally, should temporary change <app name>.testBuildType property to stagingAutoTest in ~/.gradle/gradle.properties.

Sample

You can check an example in the :test-app module.

Known issues

Dynamically referenced resources

You can see in PageObjectTest, that we referenced R.layout.page_object_1, dynamically creating layout.
These layouts referenced nowhere in app code, so if shrinkResources enabled you will face strange error:

error inflating class x
Caused by: java.lang.ClassNotFoundException: Didn't find class "android.view.x" on path: DexPathList

What it really hides, R.layout.page_object_1 got shrinked to:

<x />

If this is your case, add these resources to res/raw/keep.xml like this:

<resources xmlns:tools="http://schemas.android.com/tools"
           tools:keep="@layout/page_object*"/>

X already has a mapping

Issue #122924648 - Solved in a 1.6.x

Some issues could be solved in a new version of r8, you should consider upgrading before hacking further.

By default, r8 bundled with Android Gradle plugin, but you can override it.

buildscript {
    val r8Version: String by project

    repositories {
        maven { setUrl("http://storage.googleapis.com/r8-releases/raw") }
    }
    dependencies {
        classpath("com.android.tools:r8:$r8Version") // < it should be added before android Gradle plugin
    }
}

Info

For versions check tags here: https://r8.googlesource.com/r8/

Seems like 1.5 versions bundled with AGP 3.5.x
1.6 -> 3.6.x
and 2.0 -> 4.0.x

Warning

Don't forget to tell keeper, you are using different r8 version:

dependencies {
    keeperR8("com.android.tools:r8:$r8Version")
}

Still NoSuchMethodError

Take a look at module :subprojects:android-test:keep-for-testing for additional keep annotations.
It's a workaround described here: Issue #143419092

You still need to add proguard rules as pointed in annotation classes comments.

Why not package proguard rules?

In this case, rules go into all variants, and you only want a tested one.

Why not use original @Keep?

Just to distinguish an intent, it's for testing and only in a tested variant