diff --git a/lib/testcase/visualdiff.d.ts b/lib/testcase/visualdiff.d.ts
index 2f298eb..c7b283c 100644
--- a/lib/testcase/visualdiff.d.ts
+++ b/lib/testcase/visualdiff.d.ts
@@ -1,3 +1,4 @@
+import { Page } from '@playwright/test';
 export declare function defineVisualDiffConfig(cases: VisualDiffUrlConfig): VisualDiffTestCases;
 export declare function defaultTestFunction(testCase: VisualDiff, group: VisualDiffGroup): ({ page, context }: {
     page: any;
@@ -40,6 +41,12 @@ export type VisualDiffGroup = BaseVisualDiff & {
     pathPrefix?: string;
     testCases: VisualDiff[];
 };
+export interface MockableConstructor {
+    new (): Mockable;
+}
+export interface Mockable {
+    mock(page: Page): Promise<void>;
+}
 /**
  * An individual test case.
  */
@@ -51,6 +58,7 @@ export type BaseVisualDiff = {
     description?: string;
     representativeUrl?: string;
     skip?: SkipTest;
+    mockClass?: MockableConstructor | void;
 };
 /**
  * A declaration that a test should be skipped.
diff --git a/lib/testcase/visualdiff.js b/lib/testcase/visualdiff.js
index b303d55..956dc16 100644
--- a/lib/testcase/visualdiff.js
+++ b/lib/testcase/visualdiff.js
@@ -48,11 +48,18 @@ function defaultTestFunction(testCase, group) {
     var _this = this;
     // @ts-ignore
     return function (_a, testInfo_1) { return __awaiter(_this, [_a, testInfo_1], void 0, function (_b, testInfo) {
-        var representativeUrl, path;
+        var mock, representativeUrl, path;
         var page = _b.page, context = _b.context;
         return __generator(this, function (_c) {
             switch (_c.label) {
                 case 0:
+                    if (!(testCase.mockClass != undefined)) return [3 /*break*/, 2];
+                    mock = new testCase.mockClass;
+                    return [4 /*yield*/, mock.mock(page)];
+                case 1:
+                    _c.sent();
+                    _c.label = 2;
+                case 2:
                     // Log any errors to the Playwright console too.
                     context.on('weberror', function (webError) { return console.log(webError.error()); });
                     testInfo.annotations.push({
@@ -77,10 +84,10 @@ function defaultTestFunction(testCase, group) {
                         path = group.pathPrefix + path;
                     }
                     return [4 /*yield*/, page.goto(path)];
-                case 1:
+                case 3:
                     _c.sent();
                     return [4 /*yield*/, (0, util_1.takeAccessibleScreenshot)(page, testInfo, { fullPage: true })];
-                case 2:
+                case 4:
                     _c.sent();
                     return [2 /*return*/];
             }
diff --git a/lib/util/mock/mock.d.ts b/lib/util/mock/mock.d.ts
new file mode 100644
index 0000000..8c6cd8c
--- /dev/null
+++ b/lib/util/mock/mock.d.ts
@@ -0,0 +1,5 @@
+import { Page } from '@playwright/test';
+import { Mockable } from "../../testcase";
+export declare class Mock implements Mockable {
+    mock(page: Page): Promise<void>;
+}
diff --git a/lib/util/mock/mock.js b/lib/util/mock/mock.js
new file mode 100644
index 0000000..6f03caa
--- /dev/null
+++ b/lib/util/mock/mock.js
@@ -0,0 +1,63 @@
+"use strict";
+var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
+    return new (P || (P = Promise))(function (resolve, reject) {
+        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
+        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
+        step((generator = generator.apply(thisArg, _arguments || [])).next());
+    });
+};
+var __generator = (this && this.__generator) || function (thisArg, body) {
+    var _ = { label: 0, sent: function() { if (t[0] & 1) throw t[1]; return t[1]; }, trys: [], ops: [] }, f, y, t, g = Object.create((typeof Iterator === "function" ? Iterator : Object).prototype);
+    return g.next = verb(0), g["throw"] = verb(1), g["return"] = verb(2), typeof Symbol === "function" && (g[Symbol.iterator] = function() { return this; }), g;
+    function verb(n) { return function (v) { return step([n, v]); }; }
+    function step(op) {
+        if (f) throw new TypeError("Generator is already executing.");
+        while (g && (g = 0, op[0] && (_ = 0)), _) try {
+            if (f = 1, y && (t = op[0] & 2 ? y["return"] : op[0] ? y["throw"] || ((t = y["return"]) && t.call(y), 0) : y.next) && !(t = t.call(y, op[1])).done) return t;
+            if (y = 0, t) op = [op[0] & 2, t.value];
+            switch (op[0]) {
+                case 0: case 1: t = op; break;
+                case 4: _.label++; return { value: op[1], done: false };
+                case 5: _.label++; y = op[1]; op = [0]; continue;
+                case 7: op = _.ops.pop(); _.trys.pop(); continue;
+                default:
+                    if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) { _ = 0; continue; }
+                    if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) { _.label = op[1]; break; }
+                    if (op[0] === 6 && _.label < t[1]) { _.label = t[1]; t = op; break; }
+                    if (t && _.label < t[2]) { _.label = t[2]; _.ops.push(op); break; }
+                    if (t[2]) _.ops.pop();
+                    _.trys.pop(); continue;
+            }
+            op = body.call(thisArg, _);
+        } catch (e) { op = [6, e]; y = 0; } finally { f = t = 0; }
+        if (op[0] & 5) throw op[1]; return { value: op[0] ? op[1] : void 0, done: true };
+    }
+};
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.Mock = void 0;
+var youtube_1 = require("./youtube");
+var Mock = /** @class */ (function () {
+    function Mock() {
+    }
+    Mock.prototype.mock = function (page) {
+        var _this = this;
+        var f = function (page) { return __awaiter(_this, void 0, void 0, function () {
+            var youtube;
+            return __generator(this, function (_a) {
+                switch (_a.label) {
+                    case 0:
+                        youtube = new youtube_1.Youtube();
+                        return [4 /*yield*/, youtube.mock(page)];
+                    case 1:
+                        _a.sent();
+                        return [2 /*return*/];
+                }
+            });
+        }); };
+        return f(page);
+    };
+    return Mock;
+}());
+exports.Mock = Mock;
diff --git a/lib/util/mock/youtube.d.ts b/lib/util/mock/youtube.d.ts
new file mode 100644
index 0000000..6eb90fa
--- /dev/null
+++ b/lib/util/mock/youtube.d.ts
@@ -0,0 +1,5 @@
+import { Page } from '@playwright/test';
+import { Mockable } from "../../testcase";
+export declare class Youtube implements Mockable {
+    mock(page: Page): Promise<void>;
+}
diff --git a/lib/util/mock/youtube.js b/lib/util/mock/youtube.js
new file mode 100644
index 0000000..5909bb4
--- /dev/null
+++ b/lib/util/mock/youtube.js
@@ -0,0 +1,73 @@
+"use strict";
+var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }
+    return new (P || (P = Promise))(function (resolve, reject) {
+        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
+        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
+        function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }
+        step((generator = generator.apply(thisArg, _arguments || [])).next());
+    });
+};
+var __generator = (this && this.__generator) || function (thisArg, body) {
+    var _ = { label: 0, sent: function() { if (t[0] & 1) throw t[1]; return t[1]; }, trys: [], ops: [] }, f, y, t, g = Object.create((typeof Iterator === "function" ? Iterator : Object).prototype);
+    return g.next = verb(0), g["throw"] = verb(1), g["return"] = verb(2), typeof Symbol === "function" && (g[Symbol.iterator] = function() { return this; }), g;
+    function verb(n) { return function (v) { return step([n, v]); }; }
+    function step(op) {
+        if (f) throw new TypeError("Generator is already executing.");
+        while (g && (g = 0, op[0] && (_ = 0)), _) try {
+            if (f = 1, y && (t = op[0] & 2 ? y["return"] : op[0] ? y["throw"] || ((t = y["return"]) && t.call(y), 0) : y.next) && !(t = t.call(y, op[1])).done) return t;
+            if (y = 0, t) op = [op[0] & 2, t.value];
+            switch (op[0]) {
+                case 0: case 1: t = op; break;
+                case 4: _.label++; return { value: op[1], done: false };
+                case 5: _.label++; y = op[1]; op = [0]; continue;
+                case 7: op = _.ops.pop(); _.trys.pop(); continue;
+                default:
+                    if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) { _ = 0; continue; }
+                    if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) { _.label = op[1]; break; }
+                    if (op[0] === 6 && _.label < t[1]) { _.label = t[1]; t = op; break; }
+                    if (t && _.label < t[2]) { _.label = t[2]; _.ops.push(op); break; }
+                    if (t[2]) _.ops.pop();
+                    _.trys.pop(); continue;
+            }
+            op = body.call(thisArg, _);
+        } catch (e) { op = [6, e]; y = 0; } finally { f = t = 0; }
+        if (op[0] & 5) throw op[1]; return { value: op[0] ? op[1] : void 0, done: true };
+    }
+};
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.Youtube = void 0;
+var Youtube = /** @class */ (function () {
+    function Youtube() {
+    }
+    Youtube.prototype.mock = function (page) {
+        return __awaiter(this, void 0, void 0, function () {
+            var ytEmbedUrl;
+            var _this = this;
+            return __generator(this, function (_a) {
+                switch (_a.label) {
+                    case 0:
+                        ytEmbedUrl = new RegExp('www\.youtube\.com', 'i');
+                        return [4 /*yield*/, page.route(ytEmbedUrl, function (route) { return __awaiter(_this, void 0, void 0, function () {
+                                return __generator(this, function (_a) {
+                                    switch (_a.label) {
+                                        case 0: return [4 /*yield*/, route.fulfill({
+                                                contentType: 'text/html',
+                                                body: "\n<html>\n<head>\n    <title>Youtube Video Mock</title>\n    <style>\n        body {\n          color: white;\n          background-color: darkred;\n        }\n        div {\n          position: absolute;\n          top: 50%;\n          left: 50%;\n          margin: 0;\n          transform: translate(-50%, -50%);\n          font-size: xxx-large;\n          text-align: center;\n        }\n    </style>\n</head>\n<body>\n    <div>Youtube Video Mock</div>\n</body>\n</html>\n",
+                                            })];
+                                        case 1:
+                                            _a.sent();
+                                            return [2 /*return*/];
+                                    }
+                                });
+                            }); })];
+                    case 1:
+                        _a.sent();
+                        return [2 /*return*/];
+                }
+            });
+        });
+    };
+    return Youtube;
+}());
+exports.Youtube = Youtube;
diff --git a/package.json b/package.json
index 79ada6c..c111986 100644
--- a/package.json
+++ b/package.json
@@ -17,5 +17,6 @@
   },
   "devDependencies": {
     "typescript": "^5.2.2"
-  }
+  },
+  "packageManager": "yarn@1.22.22+sha512.a6b2f7906b721bba3d67d4aff083df04dad64c399707841b7acf00f6b133b7ac24255f2652fa22ae3534329dc6180534e98d17432037ff6fd140556e2bb3137e"
 }
diff --git a/src/testcase/visualdiff.ts b/src/testcase/visualdiff.ts
index a5e99f0..1523c84 100644
--- a/src/testcase/visualdiff.ts
+++ b/src/testcase/visualdiff.ts
@@ -1,4 +1,4 @@
-import {test, WebError} from '@playwright/test';
+import {Page, test, WebError} from '@playwright/test';
 
 import {takeAccessibleScreenshot} from "../util";
 
@@ -9,8 +9,12 @@ export function defineVisualDiffConfig(cases: VisualDiffUrlConfig) {
 export function defaultTestFunction(testCase: VisualDiff, group: VisualDiffGroup) {
   // @ts-ignore
   return async ({page, context}, testInfo) => {
-    // Log any errors to the Playwright console too.
+    if (testCase.mockClass != undefined) {
+      const mock = new testCase.mockClass;
+      await mock.mock(page);
+    }
 
+    // Log any errors to the Playwright console too.
     context.on('weberror', (webError: WebError) => console.log(webError.error()));
     testInfo.annotations.push({
       type: 'Description',
@@ -130,6 +134,13 @@ export type VisualDiffGroup = BaseVisualDiff & {
   testCases: VisualDiff[],
 }
 
+export interface MockableConstructor {
+  new (): Mockable;
+}
+export interface Mockable {
+  mock(page: Page): Promise<void>
+}
+
 /**
  * An individual test case.
  */
@@ -147,6 +158,7 @@ export type BaseVisualDiff = {
   representativeUrl?: string,
   // Allow skipping of this test.
   skip?: SkipTest,
+  mockClass?: MockableConstructor | void
 }
 
 /**
diff --git a/src/util/mock/mock.ts b/src/util/mock/mock.ts
new file mode 100644
index 0000000..c96c088
--- /dev/null
+++ b/src/util/mock/mock.ts
@@ -0,0 +1,14 @@
+import {Page} from '@playwright/test';
+import {Mockable} from "../../testcase";
+import {Youtube} from "./youtube";
+
+export class Mock implements Mockable{
+
+  mock(page: Page): Promise<void> {
+    const f = async(page: Page): Promise<void> => {
+      const youtube = new Youtube();
+      await youtube.mock(page);
+    }
+    return f(page);
+  }
+}
\ No newline at end of file
diff --git a/src/util/mock/youtube.ts b/src/util/mock/youtube.ts
new file mode 100644
index 0000000..d0a19f0
--- /dev/null
+++ b/src/util/mock/youtube.ts
@@ -0,0 +1,40 @@
+import {Page} from '@playwright/test';
+import {Mockable} from "../../testcase";
+
+export class Youtube implements Mockable{
+
+  public async mock(page: Page): Promise<void> {
+    const ytEmbedUrl = new RegExp('www\.youtube\.com', 'i');
+    await page.route(ytEmbedUrl, async route => {
+      await route.fulfill({
+        contentType: 'text/html',
+        body: `
+<html>
+<head>
+    <title>Youtube Video Mock</title>
+    <style>
+        body {
+          color: white;
+          background-color: darkred;
+        }
+        div {
+          position: absolute;
+          top: 50%;
+          left: 50%;
+          margin: 0;
+          transform: translate(-50%, -50%);
+          font-size: xxx-large;
+          text-align: center;
+        }
+    </style>
+</head>
+<body>
+    <div>Youtube Video Mock</div>
+</body>
+</html>
+`,
+      });
+    });
+  }
+
+}