How to test a method that uses package_info in Flutter?

Issue

I am writing a Flutter plugin that checks the Play Store or App Store to see if the app needs to be updated. I’m using the package_info package to determine the version of the app that the user has. My code looks like this:

getVersionStatus() {
    PackageInfo packageInfo = await PackageInfo.fromPlatform();
    localVersion = packageInfo.version;
    ...
}

I want to test this method, but if it run it as a unit test the fromPlatform call just hangs and times out the test. Is there a more elegant way to solve this than passing in a testing boolean? I.e:

if (testing) {
    PackageInfo packageInfo = await PackageInfo.fromPlatform();
    localVersion = packageInfo.version;
} else {
    localVersion = '0.0.0'
}

Should the package_info package provide a way to catch errors? Is there a way to tell if the method is being run by a test?

Solution

Like G√ľnter said, you can mock PackageInfo by installing a mock method handler in the MethodChannel for the plugin:

void packageInfoMock() {
  const MethodChannel('plugins.flutter.io/package_info').setMockMethodCallHandler((MethodCall methodCall) async {
    if (methodCall.method == 'getAll') {
      return <String, dynamic>{
        'appName': 'ABC',  // <--- set initial values here
        'packageName': 'A.B.C',  // <--- set initial values here
        'version': '1.0.0',  // <--- set initial values here
        'buildNumber': ''  // <--- set initial values here
      };
    }
    return null;
  });
}

Answered By – silvaric

Answer Checked By – Marilyn (FlutterFixes Volunteer)

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