feat: GoldenTestTheme (Betterment#124)

* wip: introduce GoldenTestTheme

* chore: regenerate goldens and add some tests

* chore: Updating Goldens

* Re-run CI after updating goldens

lib/src/alchemist_config.dart

@@ -1,6 +1,7 @@
 import 'dart:async';
 
 import 'package:alchemist/alchemist.dart';
+import 'package:alchemist/src/golden_test_theme.dart';
 import 'package:equatable/equatable.dart';
 import 'package:flutter/material.dart';
 
@@ -67,11 +68,13 @@ class AlchemistConfig extends Equatable {
   /// {@macro alchemist_config}
   const AlchemistConfig({
     bool? forceUpdateGoldenFiles,
+    GoldenTestTheme? goldenTestTheme,
     ThemeData? theme,
     PlatformGoldensConfig? platformGoldensConfig,
     CiGoldensConfig? ciGoldensConfig,
   })  : _forceUpdateGoldenFiles = forceUpdateGoldenFiles,
         _theme = theme,
+        _goldenTestTheme = goldenTestTheme,
         _platformGoldensConfig = platformGoldensConfig,
         _ciGoldensConfig = ciGoldensConfig;
 
@@ -181,6 +184,13 @@ class AlchemistConfig extends Equatable {
   ThemeData? get theme => _theme;
   final ThemeData? _theme;
 
+  /// The [GoldenTestTheme] to use when generating golden tests.
+  ///
+  /// If no [GoldenTestTheme] is provided, the default
+  /// [GoldenTestTheme.standard] will be used.
+  GoldenTestTheme? get goldenTestTheme => _goldenTestTheme;
+  final GoldenTestTheme? _goldenTestTheme;
+
   /// The configuration for human-readable golden tests running in non-CI
   /// environments.
   ///
@@ -202,12 +212,14 @@ class AlchemistConfig extends Equatable {
   AlchemistConfig copyWith({
     bool? forceUpdateGoldenFiles,
     ThemeData? theme,
+    GoldenTestTheme? goldenTestTheme,
     PlatformGoldensConfig? platformGoldensConfig,
     CiGoldensConfig? ciGoldensConfig,
   }) {
     return AlchemistConfig(
       forceUpdateGoldenFiles: forceUpdateGoldenFiles ?? _forceUpdateGoldenFiles,
       theme: theme ?? _theme,
+      goldenTestTheme: goldenTestTheme ?? _goldenTestTheme,
       platformGoldensConfig: platformGoldensConfig ?? _platformGoldensConfig,
       ciGoldensConfig: ciGoldensConfig ?? _ciGoldensConfig,
     );
@@ -224,6 +236,7 @@ class AlchemistConfig extends Equatable {
     return copyWith(
       forceUpdateGoldenFiles: other?._forceUpdateGoldenFiles,
       theme: other?._theme,
+      goldenTestTheme: other?._goldenTestTheme,
       platformGoldensConfig:
           platformGoldensConfig.merge(other?._platformGoldensConfig),
       ciGoldensConfig: ciGoldensConfig.merge(other?._ciGoldensConfig),
@@ -234,6 +247,7 @@ class AlchemistConfig extends Equatable {
   List<Object?> get props => [
         forceUpdateGoldenFiles,
         theme,
+        goldenTestTheme,
         platformGoldensConfig,
         ciGoldensConfig,
       ];

lib/src/golden_test_adapter.dart

@@ -2,6 +2,7 @@ import 'dart:async';
 import 'dart:ui' as ui;
 
 import 'package:alchemist/alchemist.dart';
+import 'package:alchemist/src/golden_test_theme.dart';
 import 'package:alchemist/src/utilities.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
@@ -164,6 +165,7 @@ abstract class GoldenTestAdapter {
     required bool obscureFont,
     required ThemeData? globalConfigTheme,
     required ThemeData? variantConfigTheme,
+    required GoldenTestTheme? goldenTestTheme,
     required PumpAction pumpBeforeTest,
     required PumpWidget pumpWidget,
     required Widget widget,
@@ -227,13 +229,16 @@ class FlutterGoldenTestAdapter extends GoldenTestAdapter {
     required bool obscureFont,
     required ThemeData? globalConfigTheme,
     required ThemeData? variantConfigTheme,
+    required GoldenTestTheme? goldenTestTheme,
     required PumpAction pumpBeforeTest,
     required PumpWidget pumpWidget,
     required Widget widget,
   }) async {
     tester.view.devicePixelRatio = 1.0;
     tester.platformDispatcher.textScaleFactorTestValue = textScaleFactor;
 
+    goldenTestTheme ??= GoldenTestTheme.standard();
+
     await pumpWidget(
       tester,
       FlutterGoldenTestWrapper(
@@ -250,7 +255,7 @@ class FlutterGoldenTestAdapter extends GoldenTestAdapter {
               child: Builder(
                 builder: (context) {
                   return ColoredBox(
-                    color: Theme.of(context).colorScheme.background,
+                    color: goldenTestTheme!.backgroundColor,
                     child: OverflowBox(
                       alignment: Alignment.topLeft,
                       minWidth: constraints.minWidth,

lib/src/golden_test_group.dart

@@ -2,6 +2,7 @@ import 'dart:math';
 
 import 'package:alchemist/alchemist.dart';
 import 'package:alchemist/src/golden_test_scenario_constraints.dart';
+import 'package:alchemist/src/golden_test_theme.dart';
 import 'package:flutter/material.dart';
 
 /// A function that receives the index of a column in a table and returns the
@@ -112,15 +113,17 @@ class GoldenTestGroup extends StatelessWidget {
       }
     }
 
+    final alchemistConfig = AlchemistConfig.current();
+    final testTheme =
+        alchemistConfig.goldenTestTheme ?? GoldenTestTheme.standard();
+
     return GoldenTestScenarioConstraints(
       constraints: scenarioConstraints,
       child: Table(
         defaultColumnWidth: const IntrinsicColumnWidth(),
         columnWidths: columnWidths,
         border: TableBorder.symmetric(
-          inside: BorderSide(
-            color: Colors.black.withOpacity(0.3),
-          ),
+          inside: BorderSide(color: testTheme.borderColor),
         ),
         children: [
           for (int i = 0; i < _effectiveRows; i++)

lib/src/golden_test_runner.dart

@@ -1,4 +1,5 @@
 import 'package:alchemist/src/golden_test_adapter.dart';
+import 'package:alchemist/src/golden_test_theme.dart';
 import 'package:alchemist/src/interactions.dart';
 import 'package:alchemist/src/pumps.dart';
 import 'package:flutter/foundation.dart';
@@ -55,6 +56,7 @@ class FlutterGoldenTestRunner extends GoldenTestRunner {
     required Widget widget,
     ThemeData? globalConfigTheme,
     ThemeData? variantConfigTheme,
+    GoldenTestTheme? goldenTestTheme,
     bool forceUpdate = false,
     bool obscureText = false,
     bool renderShadows = false,
@@ -83,6 +85,7 @@ class FlutterGoldenTestRunner extends GoldenTestRunner {
         obscureFont: obscureText,
         globalConfigTheme: globalConfigTheme,
         variantConfigTheme: variantConfigTheme,
+        goldenTestTheme: goldenTestTheme,
         pumpBeforeTest: pumpBeforeTest,
         pumpWidget: pumpWidget,
         widget: widget,

lib/src/golden_test_theme.dart

@@ -0,0 +1,32 @@
+import 'package:alchemist/src/golden_test_group.dart';
+import 'package:flutter/material.dart';
+
+/// {@template golden_test_theme}
+/// A theme that dictates the behavior and appearance of elements created
+/// by Alchemist during golden testing. This theme is used to ensure that
+/// parts of golden tests controlled by Alchemist are consistent across
+/// Flutter SDK versions.
+/// {@endtemplate}
+class GoldenTestTheme {
+  /// {@macro golden_test_theme}
+  GoldenTestTheme({
+    required this.backgroundColor,
+    required this.borderColor,
+  });
+
+  /// The standard theme for golden tests, used when no other theme is provided.
+  factory GoldenTestTheme.standard() {
+    return GoldenTestTheme(
+      // These colors are not tied to any implementation so they won't
+      // change out from under us, which would cause golden tests to fail.
+      backgroundColor: const Color(0xFF2b54a1),
+      borderColor: const Color(0xFF3d394a),
+    );
+  }
+
+  /// The background color of the golden test.
+  final Color backgroundColor;
+
+  /// The border color used to separate scenarios in a [GoldenTestGroup].
+  final Color borderColor;
+}

test/src/golden_test_adapter_test.dart

@@ -265,6 +265,7 @@ void main() {
             obscureFont: false,
             globalConfigTheme: null,
             variantConfigTheme: null,
+            goldenTestTheme: null,
             pumpBeforeTest: onlyPumpAndSettle,
             pumpWidget: onlyPumpWidget,
             widget: buildGroup(),
@@ -286,6 +287,7 @@ void main() {
             obscureFont: false,
             globalConfigTheme: null,
             variantConfigTheme: null,
+            goldenTestTheme: null,
             pumpBeforeTest: onlyPumpAndSettle,
             pumpWidget: onlyPumpWidget,
             widget: buildGroup(),
@@ -305,6 +307,7 @@ void main() {
           obscureFont: false,
           globalConfigTheme: null,
           variantConfigTheme: null,
+          goldenTestTheme: null,
           pumpBeforeTest: onlyPumpAndSettle,
           pumpWidget: onlyPumpWidget,
           widget: buildGroup(),
@@ -324,6 +327,7 @@ void main() {
             obscureFont: true,
             globalConfigTheme: globalConfigTheme,
             variantConfigTheme: variantConfigTheme,
+            goldenTestTheme: null,
             pumpBeforeTest: onlyPumpAndSettle,
             pumpWidget: onlyPumpWidget,
             widget: buildGroup(),
@@ -365,6 +369,7 @@ void main() {
           obscureFont: false,
           globalConfigTheme: null,
           variantConfigTheme: null,
+          goldenTestTheme: null,
           pumpBeforeTest: (_) async => pumpBeforeTestCalled = true,
           pumpWidget: onlyPumpWidget,
           widget: buildGroup(),
@@ -382,6 +387,7 @@ void main() {
           obscureFont: false,
           globalConfigTheme: null,
           variantConfigTheme: null,
+          goldenTestTheme: null,
           pumpBeforeTest: onlyPumpAndSettle,
           pumpWidget: (tester, widget) async {
             await onlyPumpWidget(tester, widget);

test/src/golden_test_runner_test.dart

@@ -58,6 +58,7 @@ void main() {
           obscureFont: any(named: 'obscureFont'),
           variantConfigTheme: any(named: 'variantConfigTheme'),
           globalConfigTheme: any(named: 'globalConfigTheme'),
+          goldenTestTheme: any(named: 'goldenTestTheme'),
           pumpBeforeTest: any(named: 'pumpBeforeTest'),
           pumpWidget: any(named: 'pumpWidget'),
           widget: any(named: 'widget'),
@@ -166,6 +167,7 @@ void main() {
           obscureFont: any(named: 'obscureFont'),
           globalConfigTheme: any(named: 'globalConfigTheme'),
           variantConfigTheme: any(named: 'variantConfigTheme'),
+          goldenTestTheme: any(named: 'goldenTestTheme'),
         ),
       ).thenAnswer((_) async {
         tester.view.physicalSize = Size.zero;

test/src/golden_test_test.dart

@@ -3,6 +3,7 @@ import 'dart:ui' as ui;
 import 'package:alchemist/alchemist.dart';
 import 'package:alchemist/src/golden_test_adapter.dart';
 import 'package:alchemist/src/golden_test_runner.dart';
+import 'package:alchemist/src/golden_test_theme.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:mocktail/mocktail.dart';
@@ -41,6 +42,7 @@ class FakeGoldenTestAdapter extends Mock implements GoldenTestAdapter {
     required bool obscureFont,
     required ThemeData? globalConfigTheme,
     required ThemeData? variantConfigTheme,
+    required GoldenTestTheme? goldenTestTheme,
     required PumpAction pumpBeforeTest,
     required PumpWidget pumpWidget,
     required Widget widget,