70 lines
2.4 KiB
Dart
70 lines
2.4 KiB
Dart
import 'package:flutter/material.dart';
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import 'package:flutter_test/flutter_test.dart';
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import 'package:plezy/widgets/sliver_cross_axis_layout_builder.dart';
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void main() {
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testWidgets('builder runs on width change and widget update, never from scrolling', (tester) async {
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var builderCalls = 0;
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var firstItemBuilds = 0;
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double? lastExtent;
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Widget app(double width) => MaterialApp(
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home: Center(
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child: SizedBox(
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width: width,
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height: 400,
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child: CustomScrollView(
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slivers: [
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SliverCrossAxisLayoutBuilder(
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builder: (context, crossAxisExtent) {
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builderCalls++;
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lastExtent = crossAxisExtent;
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return SliverList.builder(
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itemCount: 100,
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itemBuilder: (context, index) {
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if (index == 0) {
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return Builder(
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builder: (context) {
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firstItemBuilds++;
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return const SizedBox(height: 50);
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},
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);
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}
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return const SizedBox(height: 50);
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},
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);
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},
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),
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],
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),
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),
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),
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);
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await tester.pumpWidget(app(300));
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expect(builderCalls, 1);
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expect(lastExtent, 300);
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expect(firstItemBuilds, 1);
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// Scrolling changes SliverConstraints.scrollOffset but not the cross-axis
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// extent: the builder must not re-run, and the realized first item (still
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// within the cache extent) must not be rebuilt.
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await tester.drag(find.byType(CustomScrollView), const Offset(0, -30));
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await tester.pumpAndSettle();
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expect(builderCalls, 1, reason: 'scrolling must not re-invoke the builder');
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expect(firstItemBuilds, 1, reason: 'scrolling must not rebuild realized children');
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// A real width change re-runs the builder with the new extent.
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await tester.pumpWidget(app(250));
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await tester.pumpAndSettle();
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expect(builderCalls, 2);
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expect(lastExtent, 250);
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// Updating the widget (new builder closure from a parent rebuild) re-runs
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// it even at the same width — data changes must always propagate.
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await tester.pumpWidget(app(250));
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await tester.pumpAndSettle();
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expect(builderCalls, 3);
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});
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}
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