doormile_customer_app/test/sheet_stability_test.dart

import 'dart:async';

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

import 'package:doormile_cx/ui/widgets/states.dart';

/// ─────────────────────────────────────────────────────────────────────────
/// A SHEET DOES NOT CHANGE SIZE WHILE IT IS OPENING
///
/// Tapping BOOK NOW opened a tall sheet that snapped shorter a few frames
/// later. Nothing was wrong with either height — the sheet was simply as tall
/// as whatever [DmAsyncList] happened to be rendering, and that changes twice
/// before the customer has done anything: four skeleton rows at 302pt, then
/// the states, which are nearer 200.
///
/// The modal is still animating up while that swap happens, so the resize is
/// not a subtle reflow. It is the first thing the customer sees.
///
/// Both halves of the fix are held here: the box the list lives in keeps one
/// height across every state the list can be in, and a list handed cached
/// items renders them on the first frame instead of a skeleton over data it
/// already has.
/// ─────────────────────────────────────────────────────────────────────────
void main() {
  Widget host(Widget child) => MaterialApp(
    home: Scaffold(
      body: Center(
        child: SizedBox(width: 360, child: child),
      ),
    ),
  );

  /// A load that never finishes, so the widget stays in its loading state.
  Future<List<String>> never({bool refresh = false}) =>
      Completer<List<String>>().future;

  group('a fixed box holds its height', () {
    testWidgets('loading and loaded measure the same', (tester) async {
      const box = 300.0;

      await tester.pumpWidget(
        host(
          SizedBox(
            height: box,
            child: DmAsyncList<String>(
              skeletonRows: 3,
              load: never,
              emptyTitle: 'none',
              emptyMessage: 'none',
              builder: (_, items) => Column(children: [for (final i in items) Text(i)]),
            ),
          ),
        ),
      );
      await tester.pump();
      final loading = tester.getSize(find.byType(DmAsyncList<String>));

      await tester.pumpWidget(
        host(
          SizedBox(
            height: box,
            child: DmAsyncList<String>(
              skeletonRows: 3,
              initialItems: const ['Tamil Nadu'],
              load: never,
              emptyTitle: 'none',
              emptyMessage: 'none',
              builder: (_, items) => Column(children: [for (final i in items) Text(i)]),
            ),
          ),
        ),
      );
      await tester.pump();
      final loaded = tester.getSize(find.byType(DmAsyncList<String>));

      expect(loaded, loading, reason: 'the sheet would resize as it opened');
      expect(loading.height, box);
    });

    testWidgets('three skeleton rows fit the smallest box the clamp allows', (
      tester,
    ) async {
      // The destination sheet floors its list box at 240. Four rows are 302 and
      // overflowed it, which is why that sheet asks for three.
      await tester.pumpWidget(
        host(const SizedBox(height: 240, child: DmSkeleton(rows: 3))),
      );
      await tester.pump();
      expect(tester.takeException(), isNull);
    });
  });

  group('cached items skip the skeleton', () {
    testWidgets('the first frame is the content, not a shimmer', (
      tester,
    ) async {
      await tester.pumpWidget(
        host(
          SizedBox(
            height: 300,
            child: DmAsyncList<String>(
              initialItems: const ['Kerala'],
              load: never,
              emptyTitle: 'none',
              emptyMessage: 'none',
              builder: (_, items) =>
                  Column(children: [for (final i in items) Text(i)]),
            ),
          ),
        ),
      );
      // No settle, no extra pump: this is the frame the sheet opens on.
      expect(find.text('Kerala'), findsOneWidget);
      expect(find.byType(DmSkeleton), findsNothing);
    });

    testWidgets('without them it still loads honestly', (tester) async {
      await tester.pumpWidget(
        host(
          SizedBox(
            height: 300,
            child: DmAsyncList<String>(
              // Three for the same reason the destination sheet asks for
              // three: the default of four is 302pt and does not fit here.
              skeletonRows: 3,
              load: never,
              emptyTitle: 'none',
              emptyMessage: 'none',
              builder: (_, items) =>
                  Column(children: [for (final i in items) Text(i)]),
            ),
          ),
        ),
      );
      await tester.pump();
      expect(find.byType(DmSkeleton), findsOneWidget);
    });
  });
}