def calabash_build(app)
  apk_fingerprint = fingerprint_from_apk(app)
  log "#{app} was signed with a certificate with fingerprint #{apk_fingerprint}"

  keystores = JavaKeystore.get_keystores
  if keystores.empty?
    puts "No keystores found."
    puts "Please create one or run calabash-android setup to configure calabash-android to use an existing keystore."
    exit 1
  end
  keystore = keystores.find { |k| k.fingerprint == apk_fingerprint}

  unless keystore
    puts "#{app} is not signed with any of the available keystores."
    puts "Tried the following keystores:"
    keystores.each do |k|
      puts k.location
    end
    puts ""
    puts "You can resign the app with #{keystores.first.location} by running:
    calabash-android resign #{app}"

    puts ""
    puts "Notice that resigning an app might break some functionality."
    puts "Getting a copy of the certificate used when the app was built will in general be more reliable."

    exit 1
  end

  test_server_file_name = test_server_path(app)
  FileUtils.mkdir_p File.dirname(test_server_file_name) unless File.exist? File.dirname(test_server_file_name)

  unsigned_test_apk = File.join(File.dirname(__FILE__), '..', 'lib/calabash-android/lib/TestServer.apk')
  test_server_manifest = File.join(File.dirname(__FILE__), '..', 'lib', 'calabash-android', 'lib', 'AndroidManifest.xml')

  Dir.mktmpdir do |workspace_dir|
    Dir.chdir(workspace_dir) do
      FileUtils.cp(unsigned_test_apk, "TestServer.apk")
      FileUtils.cp(test_server_manifest, "AndroidManifest.xml")

      unless system %Q{"#{RbConfig.ruby}" -pi.bak -e "gsub(/#targetPackage#/, '#{package_name(app)}')" AndroidManifest.xml}
        raise "Could not replace package name in manifest"
      end

       unless system %Q{"#{RbConfig.ruby}" -pi.bak -e "gsub(/#testPackage#/, '#{package_name(app)}.test')" AndroidManifest.xml}
        raise "Could not replace test package name in manifest"
      end

      unless system %Q{"#{Calabash::Android::Dependencies.aapt_path}" package -M AndroidManifest.xml  -I "#{Calabash::Android::Dependencies.android_jar_path}" -F dummy.apk}
        raise "Could not create dummy.apk"
      end

      Calabash::Utils.with_silent_zip do
        Zip::File.new("dummy.apk").extract("AndroidManifest.xml","customAndroidManifest.xml")
        Zip::File.open("TestServer.apk") do |zip_file|
          begin
            check_file("AndroidManifest.xml")
            manifest_exists = true
          rescue
            manifest_exists = false
          end

          if manifest_exists
            zip_file.remove("AndroidManifest.xml")
          end

          zip_file.add("AndroidManifest.xml", "customAndroidManifest.xml")
        end
      end
    end
    keystore.sign_apk("#{workspace_dir}/TestServer.apk", test_server_file_name)
    begin

    rescue => e
      log e
      raise "Could not sign test server"
    end
  end
  puts "Done signing the test server. Moved it to #{test_server_file_name}"
end