ParcelTester.kt

import android.os.Parcel
import android.os.Parcelable
import org.assertj.core.api.Assertions.assertThat

/**
 * A test for parcelable implementations
 */
class ParcelTester<T : Parcelable>(klazz: Class<T>) {

  // access the creator through reflection like android does
  @Suppress("UNCHECKED_CAST")
  val creator = klazz.getField("CREATOR").get(null) as Parcelable.Creator<T>

  // wraps a type to a parcel
  fun wrap(value: T): Parcel {
    val parcel = Parcel.obtain()
    value.writeToParcel(parcel, 0)
    parcel.setDataPosition(0)
    return parcel
  }

  // unwraps a parcel
  fun unwrap(parcel: Parcel): T = creator.createFromParcel(parcel)

  fun repackageAndVerifyDataPosition(value: T): T {
    val wrapped = wrap(value)
    val unwrapped = unwrap(wrapped)

    // check that the whole parcel was consumed
    assertThat(wrapped.dataPosition()).isEqualTo(wrapped.dataSize())

    return unwrapped
  }

  // test that the value is equal to itself after wrapping and unwrapping
  fun test(value: T) {
    val unwrapped = repackageAndVerifyDataPosition(value)
    assertThat(value).isEqualTo(unwrapped)
  }
}