1 files changed, 58 insertions, 0 deletions
diff --git a/testing/web-platform/tests/css/css-paint-api/resources/utils.js b/testing/web-platform/tests/css/css-paint-api/resources/utils.js
new file mode 100644
index 0000000000..e968644136
--- /dev/null
+++ b/testing/web-platform/tests/css/css-paint-api/resources/utils.js
@@ -0,0 +1,58 @@
+
+// Register a property, and interpolate its value to the halfway point.
+function registerAndInterpolateProperty(options) {
+  CSS.registerProperty({
+    name: options.name,
+    syntax: `${options.syntax} | none`,
+    initialValue: 'none',
+    inherits: false
+  });
+  let animation = options.on.animate([
+    { [options.name]: options.from },
+    { [options.name]: options.to }
+  ], 1000);
+  animation.currentTime = 500;
+  animation.pause();
+}
+
+// Apply a paint worklet to 'target' which verifies that the worklet-side value
+// of a set of properties is what we expect.
+//
+// The 'expected' parameter is an object where each key is the name of a
+// property to check, and each corresponding value is an array with the expected
+// (serialized) values for that property.
+function expectWorkletValues(target, expected) {
+  const workletName = 'registered-property-value';
+
+  // Wrap any single values in an array. This makes it possible to omit the
+  // array if there is only one value.
+  const ensureArray = x => x.constructor === Array ? x : [x];
+  expected = Object.entries(expected).map(([k, v]) => [k, ensureArray(v)])
+                                     .map(x => ({[x[0]]: x[1]}))
+                                     .reduce((a, b) => Object.assign(a, b), {});
+
+  target.style.setProperty('width', '100px');
+  target.style.setProperty('height', '100px');
+  target.style.setProperty('background-image', `paint(${workletName})`);
+
+  const worklet = `
+    const expectedData = ${JSON.stringify(expected)};
+    const expectedKeys = Object.keys(expectedData).sort();
+    registerPaint('${workletName}', class {
+      static get inputProperties() { return expectedKeys; }
+      paint(ctx, geom, styleMap) {
+        let serialize = (v) => '[' + v.constructor.name + ' ' + v.toString() + ']';
+        let actual = expectedKeys.map(k => styleMap.getAll(k).map(serialize).join(', ')).join(' | ');
+        let expected = expectedKeys.map(k => expectedData[k].join(', ')).join(' | ');
+        ctx.fillStyle = (actual === expected) ? 'green' : 'red';
+        ctx.fillRect(0, 0, geom.width, geom.height);
+      }
+    });`
+
+  importWorkletAndTerminateTestAfterAsyncPaint(CSS.paintWorklet, worklet);
+}
+
+// Like expectWorkletValues, but can only test a single property.
+function expectWorkletValue(target, property, expected) {
+  expectWorkletValues(target, { [property]: expected });
+}