[rfw, ci] Regenerate goldens, manually roll #4835

.ci/flutter_master.version

@@ -1 +1 @@
-c175cf87a6a3d797fdc3f81cbd54419f639cd3d9
+685ce14b2d0f4046bd596842208d0c17f9a21e57

packages/rfw/.gitignore

@@ -1,3 +1,6 @@
+# Ignore golden test failure files
+test/failures/*.png
+
 # Miscellaneous
 *.class
 *.log

packages/rfw/README.md

@@ -991,3 +991,34 @@ exclude that line from the coverage calculation.
 Golden tests are only run against the Flutter master channel and only
 run on Linux, since minor rendering differences are expected on
 different platforms and on different versions of Flutter.
+
+### When goldens fail
+
+When golden tests fail, several files will be created in a `test/failures`
+directory.
+
+The suffix of each file briefly describes its contents:
+
+* `_masterImage`: The current golden against which comparisons are being made.
+* `_testImage`: The image generated by this run of the test.
+* `_isolatedDiff`: An image where only the pixels that differ between the
+  master and test images are rendered.
+* `_maskedDiff`: An image where the pixels that differ between the master and
+  test images are rendered in black (isolatedDiff + maskedDiff = testImage).
+
+Check the `_testImage` and the `Diff`s and see if the changes are valid. From
+time to time, a new dithering or anti-aliasing algorithm will land in Flutter
+that will invalidate a bunch of goldens, but not really break the rendering.
+
+In this case, you may update the golden files.
+
+### Updating goldens
+
+Once you've validated that the new goldens make sense, you may update the
+goldens by calling `run_tests.sh --update-goldens`.
+
+That should update the reference golden images in the `test/goldens` directory.
+
+Read more about Golden matching [in `package:flutter_test` API docs][package-test].
+
+[package-test]: https://api.flutter.dev/flutter/flutter_test/matchesGoldenFile.html

packages/rfw/run_tests.sh

@@ -9,4 +9,5 @@
 
 set -e
 pushd test_coverage; dart pub get; popd
-dart --enable-asserts test_coverage/bin/test_coverage.dart
+set -x
+dart --enable-asserts test_coverage/bin/test_coverage.dart "$@"

packages/rfw/test_coverage/bin/test_coverage.dart

@@ -57,8 +57,13 @@ Future<void> main(List<String> arguments) async {
 
   final ProcessResult result = Process.runSync(
     'flutter',
-    <String>['test', '--coverage'],
+    <String>[
+      'test', '--coverage',
+      if (arguments.isNotEmpty)
+        ...arguments,
+    ],
   );
+
   if (result.exitCode != 0) {
     print(result.stdout);
     print(result.stderr);