fix: Reset pixel ratio and textScaleFactor values on tearDown

[jamesblasco]

Is there an existing issue for this?

• I have searched the existing issues.

Version

0.4.1

Description

The method FlutterGoldenTestAdapter.pumpGoldenTest sets a new pixelRatio and textScalorFactor test values that are not reset to the original values on tear down. This makes the test that run after a golden test to have modified properties that can alter the result of the test.

alchemist/lib/src/golden_test_adapter.dart

Lines 226 to 228 in a80c62c

	tester.binding.window.devicePixelRatioTestValue = 1.0;
	tester.binding.window.platformDispatcher.textScaleFactorTestValue =
	textScaleFactor;

We should clear values on tearDown:

addTearDown(() {
   tester.binding.window.clearDevicePixelRatioTestValue();
   tester.binding.platformDispatcher.clearTextScaleFactorTestValue();
});

Steps to reproduce

When running the following code, goldenTest sets up a new devicePixelRatio and the test after it fail.

import 'package:alchemist/alchemist.dart';
import 'package:flutter/widgets.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {
  testWidgets('before golden devicePixelRatio', (tester) async {
    expect(tester.binding.window.devicePixelRatio, 3);
  });

  goldenTest(
    'A',
    fileName: 'a',
    builder: () => Container(height: 300),
  );

  testWidgets('after golden devicePixelRatio', (tester) async {
    expect(tester.binding.window.devicePixelRatio, 3);  // Fails with actual value 1
  });
}

Expected behavior

When clearing devicePixelRatio on tearDown, the test work as expected

import 'package:alchemist/alchemist.dart';
import 'package:flutter/widgets.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {
  testWidgets('before golden devicePixelRatio', (tester) async {
    expect(tester.binding.window.devicePixelRatio, 3);
  });

  goldenTest(
    'A',
    fileName: 'a',
    builder: () => Container(height: 300),
    whilePerforming: (tester) async {
      addTearDown(() {
        tester.binding.window.clearDevicePixelRatioTestValue();
      });
      return;
    },
  );

  testWidgets('after golden devicePixelRatio', (tester) async {
    expect(tester.binding.window.devicePixelRatio, 3);
  });
}

Screenshots

Additional context and comments

No response

[Kirpal]

Can you try this again? I just ran your expected behavior example on the latest version of Alchemist and it all passes.