Unit testing in Flutter passing BuildContext

One way is to use testWidgets in combination with a Builder widget:

testWidgets('me testing', (WidgetTester tester) async {
  await tester.pumpWidget(
    Builder(
      builder: (BuildContext context) {
        var actual = sut.myMethodName(context, ...);
        expect(actual, something);

        // The builder function must return a widget.
        return Placeholder();
      },
    ),
  );
});