Unit test Android custom view with AndroidX Test and Robolectric

build.gradle

android {

    defaultConfig {
        ...
    }

    testOptions {
        unitTests.includeAndroidResources = true
    }
}

dependencies {
    ...

    testImplementation 'junit:junit:4.12'
    testImplementation 'org.robolectric:robolectric:4.3.1'
    testImplementation 'androidx.test:core:1.2.0'
    testImplementation "com.google.truth:truth:1.0.1"
}