test: skip baseline rewrite on sub-threshold drift in update mode (#11628) (#11634)

Co-authored-by: Serhii Kulykov <iamkulykov@gmail.com>

Author: vaadin-bot

patches/@web+test-runner-visual-regression+0.10.0.patch

@@ -1,3 +1,30 @@
+diff --git a/node_modules/@web/test-runner-visual-regression/dist/visualDiffCommand.js b/node_modules/@web/test-runner-visual-regression/dist/visualDiffCommand.js
+index 08b4d27..423aa5a 100644
+--- a/node_modules/@web/test-runner-visual-regression/dist/visualDiffCommand.js
++++ b/node_modules/@web/test-runner-visual-regression/dist/visualDiffCommand.js
+@@ -40,6 +40,22 @@ async function visualDiffCommand(options, image, name, { browser, testFile }) {
+         name: baselineName,
+     });
+     if (options.update) {
++        // Skip rewriting the baseline if the new image is already within the
++        // configured diff threshold. Sub-perceptual drift (1-LSB Chromium
++        // rasterizer rounding, anti-alias jitter on shadows / translucent
++        // layers) leaves the existing baseline untouched, avoiding 800+
++        // file rewrites on every browser bump.
++        if (baselineImage) {
++            const updateResult = await options.getImageDiff({
++                name,
++                baselineImage,
++                image,
++                options: options.diffOptions,
++            });
++            if (!updateResult.error && passesFailureThreshold(updateResult, options).passed) {
++                return { diffPercentage: updateResult.diffPercentage, passed: true };
++            }
++        }
+         await options.saveBaseline({
+             filePath: resolveImagePath(baseDir, baselineName),
+             baseDir,
 diff --git a/node_modules/@web/test-runner-visual-regression/index.d.ts b/node_modules/@web/test-runner-visual-regression/index.d.ts
 index f540538..5198ffa 100644
 --- a/node_modules/@web/test-runner-visual-regression/index.d.ts

wtr-utils.js

@@ -312,6 +312,7 @@ const createVisualTestsConfig = (theme) => {
         getFailedName(args) {
           return getScreenshotFileName(args, 'failed');
         },
+        diffOptions: { threshold: 0.2 },
         failureThreshold: 0.05,
         failureThresholdType: 'percent',
         update: process.env.TEST_ENV === 'update',