// Copyright 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
import 'dart:async';
import 'dart:io';
import 'dart:math' as math;
import 'dart:typed_data';
import 'package:image/image.dart';
import 'package:path/path.dart' as path;
import 'package:test_api/test_api.dart' as test_package show TestFailure;
import 'goldens.dart';
/// The default [GoldenFileComparator] implementation for `flutter test`.
///
/// The term __golden file__ refers to a master image that is considered the true
/// rendering of a given widget, state, application, or other visual
/// representation you have chosen to capture. This comparator loads golden
/// files from the local file system, treating the golden key as a relative
/// path from the test file's directory.
///
/// This comparator performs a pixel-for-pixel comparison of the decoded PNGs,
/// returning true only if there's an exact match. In cases where the captured
/// test image does not match the golden file, this comparator will provide
/// output to illustrate the difference, described in further detail below.
///
/// When using `flutter test --update-goldens`, [LocalFileComparator]
/// updates the golden files on disk to match the rendering.
///
/// ## Local Output from Golden File Testing
///
/// The [LocalFileComparator] will output test feedback when a golden file test
/// fails. This output takes the form of differential images contained within a
/// `failures` directory that will be generated in the same location specified
/// by the golden key. The differential images include the master and test
/// images that were compared, as well as an isolated diff of detected pixels,
/// and a masked diff that overlays these detected pixels over the master image.
///
/// The following images are examples of a test failure output:
///
/// | File Name | Image Output |
/// |----------------------------|---------------|
/// | testName_masterImage.png |  |
/// | testName_testImage.png |  |
/// | testName_isolatedDiff.png |  |
/// | testName_maskedDiff.png |  |
///
/// See also:
///
/// * [GoldenFileComparator], the abstract class that [LocalFileComparator]
/// implements.
/// * [matchesGoldenFile], the function from [flutter_test] that invokes the
/// comparator.
class LocalFileComparator extends GoldenFileComparator {
/// Creates a new [LocalFileComparator] for the specified [testFile].
///
/// Golden file keys will be interpreted as file paths relative to the
/// directory in which [testFile] resides.
///
/// The [testFile] URL must represent a file.
LocalFileComparator(Uri testFile, {path.Style pathStyle})
: basedir = _getBasedir(testFile, pathStyle),
_path = _getPath(pathStyle);
static path.Context _getPath(path.Style style) {
return path.Context(style: style ?? path.Style.platform);
}
static Uri _getBasedir(Uri testFile, path.Style pathStyle) {
final path.Context context = _getPath(pathStyle);
final String testFilePath = context.fromUri(testFile);
final String testDirectoryPath = context.dirname(testFilePath);
return context.toUri(testDirectoryPath + context.separator);
}
/// The directory in which the test was loaded.
///
/// Golden file keys will be interpreted as file paths relative to this
/// directory.
final Uri basedir;
/// Path context exists as an instance variable rather than just using the
/// system path context in order to support testing, where we can spoof the
/// platform to test behaviors with arbitrary path styles.
final path.Context _path;
@override
Future<bool> compare(Uint8List imageBytes, Uri golden) async {
final File goldenFile = _getGoldenFile(golden);
if (!goldenFile.existsSync()) {
throw test_package.TestFailure('Could not be compared against non-existent file: "$golden"');
}
final List<int> goldenBytes = await goldenFile.readAsBytes();
final ComparisonResult result = GoldenFileComparator.compareLists(imageBytes, goldenBytes);
if (!result.passed) {
String additionalFeedback = '';
if (result.diffs != null) {
additionalFeedback = '\nFailure feedback can be found at ${path.join(basedir.path, 'failures')}';
final Map<String, Object> diffs = result.diffs;
diffs.forEach((String name, Object untypedImage) {
final Image image = untypedImage;
final File output = _getFailureFile(name, golden);
output.parent.createSync(recursive: true);
output.writeAsBytesSync(encodePng(image));
});
}
throw test_package.TestFailure('Golden "$golden": ${result.error}$additionalFeedback');
}
return result.passed;
}
@override
Future<void> update(Uri golden, Uint8List imageBytes) async {
final File goldenFile = _getGoldenFile(golden);
await goldenFile.parent.create(recursive: true);
await goldenFile.writeAsBytes(imageBytes, flush: true);
}
File _getGoldenFile(Uri golden) {
return File(_path.join(_path.fromUri(basedir), _path.fromUri(golden.path)));
}
File _getFailureFile(String failure, Uri golden) {
final String fileName = golden.pathSegments[0];
final String testName = fileName.split(path.extension(fileName))[0]
+ '_'
+ failure
+ '.png';
return File(_path.join(
_path.fromUri(basedir),
_path.fromUri(Uri.parse('failures/$testName')),
));
}
}
/// Returns a [ComparisonResult] to describe the pixel differential of the
/// [test] and [master] image bytes provided.
ComparisonResult compareLists(List<int> test, List<int> master) {
if (identical(test, master))
return ComparisonResult(passed: true);
if (test == null || master == null || test.isEmpty || master.isEmpty) {
return ComparisonResult(
passed: false,
error: 'Pixel test failed, null image provided.',
);
}
final Image testImage = decodePng(test);
final Image masterImage = decodePng(master);
assert(testImage != null);
assert(masterImage != null);
final int width = testImage.width;
final int height = testImage.height;
if (width != masterImage.width || height != masterImage.height) {
return ComparisonResult(
passed: false,
error: 'Pixel test failed, image sizes do not match.\n'
'Master Image: ${masterImage.width} X ${masterImage.height}\n'
'Test Image: ${testImage.width} X ${testImage.height}',
);
}
int pixelDiffCount = 0;
final int totalPixels = width * height;
final Image invertedMaster = invert(Image.from(masterImage));
final Image invertedTest = invert(Image.from(testImage));
final Map<String, Image> diffs = <String, Image>{
'masterImage' : masterImage,
'testImage' : testImage,
'maskedDiff' : Image.from(testImage),
'isolatedDiff' : Image(width, height),
};
for (int x = 0; x < width; x++) {
for (int y =0; y < height; y++) {
final int testPixel = testImage.getPixel(x, y);
final int masterPixel = masterImage.getPixel(x, y);
final int diffPixel = (getRed(testPixel) - getRed(masterPixel)).abs()
+ (getGreen(testPixel) - getGreen(masterPixel)).abs()
+ (getBlue(testPixel) - getBlue(masterPixel)).abs()
+ (getAlpha(testPixel) - getAlpha(masterPixel)).abs();
if (diffPixel != 0 ) {
final int invertedMasterPixel = invertedMaster.getPixel(x, y);
final int invertedTestPixel = invertedTest.getPixel(x, y);
final int maskPixel = math.max(invertedMasterPixel, invertedTestPixel);
diffs['maskedDiff'].setPixel(x, y, maskPixel);
diffs['isolatedDiff'].setPixel(x, y, maskPixel);
pixelDiffCount++;
}
}
}
if (pixelDiffCount > 0) {
return ComparisonResult(
passed: false,
error: 'Pixel test failed, ${((pixelDiffCount/totalPixels) * 100).toStringAsFixed(2)}% diff detected.',
diffs: diffs,
);
}
return ComparisonResult(passed: true);
}