encodings[ 0x1d] = encoding // Group Separator
      encodings[ 0x1e] = encoding // Record Separator
      encodings[ 0x1f] = encoding // Unit Separator
      encodings[ 0x7f] = encoding // Delete
    }

  fun nonAscii(encoding: Encoding) =
    apply {
      encodings[UNICODE_2] = encoding
      encodings[UNICODE_3] = encoding
      encodings[UNICODE_4] = encoding
    }

  fun test(component: Component) =
    apply {

    // lock it down due to URL templating: "http://{env}.{dc}.example.com".
    UrlComponentEncodingTester.newInstance()
      .nonPrintableAscii(Encoding.FORBIDDEN)
      .nonAscii(Encoding.PUNYCODE)
      .override(
        Encoding.FORBIDDEN,
        '\t'.code,
        '\n'.code,
        '\u000c'.code,
        '\r'.code,
        ' '.code,
      )
      .override(

			// For Format detection, check if block is properly formatted since
			// the parser is more liberal than what USTAR actually permits.
			notASCII := func(r rune) bool { return r >= 0x80 }
			if bytes.IndexFunc(tr.blk[:], notASCII) >= 0 {
				hdr.Format = FormatUnknown // Non-ASCII characters in block.
			}
			nul := func(b []byte) bool { return int(b[len(b)-1]) == 0 }