Testing room migration, Cannot find the schema file in the assets folder [room-migration]

Question

This issue came after I decided to add another entity to the room database. The schema is being exported in the expected directory. All build.gradle setting is done and seems to be working but is not. Since I got:

java.io.FileNotFoundException: Cannot find the schema file in the assets folder. Make sure to include the exported json schemas in your test assert inputs. 
See https://developer.android.com/training/data-storage/room/migrating-db-versions#export-schema for details. Missing file: com.company.companyapp.db.AppStore/1.json

In fact both json schemas are being generated but the test runner is not able to find such files. Here is the gradle setup:

testOptions.unitTests.includeAndroidResources = true

defaultConfig {
    ...
    multiDexEnabled true
    javaCompileOptions {
        annotationProcessorOptions {
            arguments = ["room.schemaLocation": "$projectDir/store".toString()]
        }
    }

    testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    android.compileOptions.sourceCompatibility 1.8
    android.compileOptions.targetCompatibility 1.8
}

sourceSets {
    androidTest.assets.srcDirs += files("$projectDir/store".toString())
}

dependencies {
    def roomVersion = '2.2.1'
    // Other deps ...
    implementation "androidx.room:room-runtime:$roomVersion"
    implementation "androidx.room:room-rxjava2:$roomVersion"
    annotationProcessor "androidx.room:room-compiler:$roomVersion"
    testImplementation "androidx.room:room-testing:$roomVersion"

    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
    androidTestImplementation "androidx.test:core:$testCoreVersion"
    androidTestImplementation "androidx.test.ext:junit:$extJUnitVersion"
    testImplementation "androidx.test:core:$testCoreVersion"
    testImplementation "androidx.test.ext:junit:$extJUnitVersion"
    testImplementation "org.robolectric:robolectric:4.2.1"
}

I also note the Studio IDE marks the json schema directory holder

By looking at the google room migration examples I can see there is a difference, and not talking about the name.

So it's very clear the gradle plugin is doing something different than I spect or the documentation says it should work, but it doesn't.

at androidx.room.testing.MigrationTestHelper.loadSchema(MigrationTestHelper.java:320)
at androidx.room.testing.MigrationTestHelper.createDatabase(MigrationTestHelper.java:152)
at com.company.companyapp.MigrationTest.migrate1To2(MigrationTest.java:32)

Answer 1

Using this workaround found by PaulWoitaschek works for me with Robolectric 4.3:

add schemas dir on debug souceSets on your app's build.gradle

Groovy

    sourceSets {
        debug.assets.srcDirs += files("$projectDir/schemas".toString())
    }

Kotlin DSL

    sourceSets {
        getByName("debug").assets.srcDirs(files("$projectDir/schemas")) // Room
    }

Answer 2

Please also make sure while creating the MigrationTestHelper to insert the actual database.class. I got confused and set my Entity.class instead, leading to the same error.