doormile_customer_app/test/page_transition_test.dart

import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';

import 'package:doormile_cx/main.dart';
import 'package:doormile_cx/ui/screens/booking/booking_routes.dart';

/// ─────────────────────────────────────────────────────────────────────────
/// WHICH WAY A PAGE LEAVES
///
/// The app's pages used to arrive from the right and leave to the right, which
/// is the direction the system back gesture drags — a page that slides off
/// sideways under a button press reads as a swipe the customer did not make.
///
/// They now rise from the bottom and fall back down it. A golden cannot see
/// motion, so this is where that direction is held: mid-push the incoming page
/// is *below* where it lands and exactly on its horizontal mark, and mid-pop it
/// is on its way back down rather than off to one side.
/// ─────────────────────────────────────────────────────────────────────────
void main() {
  const key = ValueKey('pushed-page');

  Future<void> pumpApp(WidgetTester tester) async {
    await tester.pumpWidget(
      MaterialApp(
        theme: buildDoormileTheme(),
        home: Builder(
          builder: (context) => Scaffold(
            body: Center(
              child: TextButton(
                onPressed: () => Navigator.of(context).push(
                  bookingRoute<void>(
                    'x',
                    (_) => const Scaffold(
                      key: key,
                      body: Center(child: Text('second')),
                    ),
                  ),
                ),
                child: const Text('go'),
              ),
            ),
          ),
        ),
      ),
    );
  }

  /// Where the pushed page's top-left corner currently sits.
  Offset cornerOf(WidgetTester tester) =>
      tester.getTopLeft(find.byKey(key).first);

  testWidgets('a push arrives from below, not from the side', (tester) async {
    await pumpApp(tester);
    final screen = tester.view.physicalSize / tester.view.devicePixelRatio;

    await tester.tap(find.text('go'));
    await tester.pump();
    // Partway through the 420ms push.
    await tester.pump(const Duration(milliseconds: 120));

    final corner = cornerOf(tester);
    expect(
      corner.dy,
      greaterThan(0),
      reason: 'the arriving page should still be below its resting place',
    );
    expect(
      corner.dy,
      lessThan(screen.height),
      reason: 'and already on screen, not still parked off the bottom',
    );
    expect(
      corner.dx,
      0,
      reason: 'nothing travels horizontally any more',
    );

    await tester.pumpAndSettle();
    expect(cornerOf(tester), Offset.zero);
  });

  testWidgets('back drops the page down the screen', (tester) async {
    await pumpApp(tester);
    await tester.tap(find.text('go'));
    await tester.pumpAndSettle();

    final settled = cornerOf(tester);
    expect(settled, Offset.zero);

    // The back button, not a gesture.
    final popped = tester.state<NavigatorState>(find.byType(Navigator));
    popped.pop();
    await tester.pump();
    await tester.pump(const Duration(milliseconds: 120));

    final leaving = cornerOf(tester);
    expect(
      leaving.dy,
      greaterThan(0),
      reason: 'the page being left should be heading down, not up',
    );
    expect(
      leaving.dx,
      0,
      reason: 'and not sideways, which is what it used to do',
    );
  });

  testWidgets('it travels the whole height, so the direction is readable', (
    tester,
  ) async {
    await pumpApp(tester);
    final screen = tester.view.physicalSize / tester.view.devicePixelRatio;

    await tester.tap(find.text('go'));
    await tester.pump();
    // One frame in: the page has barely moved, so it is still near the bottom
    // edge. A 14%-of-the-width nudge — what this replaced — would put it within
    // a few points of its resting place by now.
    await tester.pump(const Duration(milliseconds: 16));

    expect(
      cornerOf(tester).dy,
      greaterThan(screen.height * 0.5),
      reason: 'a token nudge has no direction a customer can name',
    );
  });

  testWidgets('going back is quicker than going forward', (tester) async {
    final route = bookingRoute<void>('x', (_) => const SizedBox()) as DmPageRoute;
    expect(route.transitionDuration, const Duration(milliseconds: 420));
    expect(route.reverseTransitionDuration, const Duration(milliseconds: 340));
    expect(
      route.reverseTransitionDuration < route.transitionDuration,
      isTrue,
      reason: 'the customer already knows what is behind them',
    );
  });
}