What the right way of launching app in integration test?

Question

I'm using the flutter integration driver for flutter mobile automation.

In this regard, I want to understand the recommended approach of calling app.main in the integration test.

Let's take two below examples:

//imports

void main() {
  IntegrationTestWidgetsFlutterBinding.ensureInitialized();

  group('sanity test suite', () {

    //runs before each test
    setUp(() async {
      SLogger.i('running before test.!');
      app.main();
      SLogger.i('App opened');

    });

    testWidgets('sample test', (tester) async {
      //some validations
    });

    testWidgets('check value increments', (tester) async {
      //some validations
    });

    testWidgets('check integration test page', (tester) async {
      //some validations
    });
  });
}

In the above code snippet, I'm calling app.main in setUp() method which is executed before each test run. With this, i'm getting below error while executing the second test

I/flutter (18595): The following assertion was thrown running a test:
I/flutter (18595): A FocusManager was used after being disposed of.
I/flutter (18595): Once you have called dispose() on a FocusManager, it can no longer be used.
I/flutter (18595): 

Now, let's look into another snippet where I'm calling app.main in each testWidgets. which is perfectly working fine executing all the tests.!

//imports

void main() {
  IntegrationTestWidgetsFlutterBinding.ensureInitialized();

  group('sanity test suite', () {

    testWidgets('sample test', (tester) async {
      app.main();
      // some validations
    });

    testWidgets('check value increments', (tester) async {
      app.main();
      // some validations
    });

    testWidgets('check integration test page', (tester) async {             app.main();
      // some validations
    });
  });
}

Which one is the right approach?