printTestLabel method
Prints a test label
macAddress MAC address of the printer
Returns result message if successful, throws an error if failed
Implementation
Future<String> printTestLabel(String macAddress) async {
String testZpl = """^XA
^PON
^PW400
^MMT
^PR0
^LH0,6
^PMN
^FO50,50
^A0N,50,50
^FDZebra Test Print^FS
^FO50,120
^A0N,30,30
^FDDate: ${DateTime.now()}^FS
^FO50,170
^A0N,30,30
^FDTest Successful!^FS
^PQ1,0,1,Y
^XZ""";
return sendZplToPrinter(macAddress, testZpl);
}