testing library

Fakes that stand in for the platform, so a tap can be exercised in a test. Test code only.

This library exists for a hardware reason rather than a convenience one. NFCTagReaderSession does not start in the Simulator and no emulator has an NFC radio, so replacing the platform side is the only mechanism by which any CI runs a tag through an app at all. Everything here is inert -- no channel is touched, no session is started, and no handle addresses a tag -- so an app that reaches for it from its own lib/ ships that inertness to its users.

debugReplaceApis puts a fake platform in place and hands back the function that puts the real one back; fakeNfcTag builds the tag the platform would have delivered; and the three Fake*HostApi classes answer every call, so a test writes only the ones it cares about.

import 'dart:typed_data';

import 'package:flutter_test/flutter_test.dart';
import 'package:nfc_util/android.dart';
import 'package:nfc_util/testing.dart';

class _Card extends FakeNfcAndroidHostApi {
  @override
  Future<Uint8List> mifareClassicReadBlock(String handle, int blockIndex) async =>
      Uint8List.fromList(List.filled(16, blockIndex));
}

void main() {
  late void Function() restore;
  setUp(() => restore = debugReplaceApis(android: _Card()));
  tearDown(() => restore());

  test('reads the block it asked for', () async {
    final tag = fakeNfcTag(techs: [FakeTech.nfcA(), FakeTech.mifareClassic()]);
    expect(await MifareClassic.from(tag)!.readBlock(blockIndex: 4), everyElement(4));
  });
}

One thing this library deliberately does not hand over: the generated wire classes. Every call that answers a plain Dart value -- the transceives, the Mifare reads, the capability questions -- can be overridden with nothing but the import above, but a call that names a generated class or enum anywhere in its signature can only be overridden by a test that imports package:nfc_util/src/pigeon.g.dart itself. That covers more than the obvious return types: ndefRead and the ISO 7816 exchanges answer one, and resetTech and the card-emulation queries answer nothing at all but still take one as a parameter. That is an implementation import the analyzer flags, and a shape that changes without a major version, which is why it is not re-exported from here. Say it with a public type where the two are interchangeable -- a message handed to FakeTech.ndefAndroid and read back as Ndef.from(tag)?.cachedMessage, rather than an overridden ndefRead -- and where they are not, the import is the price.

Classes

Functions

nfc_util package

testing library