Future<TestGesture> down(Point downLocation, { int pointer: 1, HitTester hitTester, EventDispatcher dispatcher })

Create a TestGesture by starting with a pointerDown at the given point.

By default, the pointer ID used is 1. This can be overridden by providing the pointer argument.

A function to use for hit testing should be provided via the hitTester argument, and a function to use for dispatching events should be provided via the dispatcher argument.

Source 

static Future<TestGesture> down(Point downLocation, {
  int pointer: 1,
  HitTester hitTester,
  EventDispatcher dispatcher
}) async {
  assert(hitTester != null);
  assert(dispatcher != null);
  final Completer<TestGesture> completer = new Completer<TestGesture>();
  TestGesture result;
  TestAsyncUtils.guard(() async {
    // dispatch down event
    final HitTestResult hitTestResult = hitTester(downLocation);
    final TestPointer testPointer = new TestPointer(pointer);
    await dispatcher(testPointer.down(downLocation), hitTestResult);

    // create a TestGesture
    result = new TestGesture._(dispatcher, hitTestResult, testPointer);
    return null;
  }).whenComplete(() {
    completer.complete(result);
  });
  return completer.future;
}