tests.sbt

import android.Keys._

TaskKey[Unit]("check-for-properties") <<= (apkFile) map { a =>
  val found = findInArchive(a) (_.getName == "com/example/lib/file.properties")
  if (!found) error("Properties not found in APK")
}

def findInArchive(archive: File)(predicate: String => Boolean): Boolean = {
  import java.io._
  import java.util.zip._
  val in = new ZipInputStream(new FileInputStream(archive))
  val found = Stream.continually(in.getNextEntry) takeWhile (
    _ != null) exists predicate
  in.close()
  found
}