LibWeb: Add a test-only API to spoof the current URL and origin

This is not that easy to use for test developers, as forgetting to set
the url back to its original state after testing your specific API will
cause future navigations to fail in inexplicable ways.

Tests/LibWeb/Text/expected/all-window-properties.txt

@@ -383,12 +383,14 @@ XMLHttpRequest
 XMLHttpRequestEventTarget
 XMLHttpRequestUpload
 XMLSerializer
+__finishTest
 __preventMultipleTestFunctions
 animationFrame
 asyncTest
 printElement
 println
 promiseTest
+spoofCurrentURL
 test
 timeout
 webkitURL

Tests/LibWeb/Text/input/include.js

@@ -1,5 +1,6 @@
 var __outputElement = null;
 let __alreadyCalledTest = false;
+let __originalURL = null;
 function __preventMultipleTestFunctions() {
     if (__alreadyCalledTest) {
         throw new Error("You must only call test() or asyncTest() once per page");
@@ -10,9 +11,24 @@ function __preventMultipleTestFunctions() {
 if (globalThis.internals === undefined) {
     internals = {
         signalTextTestIsDone: function () {},
+        spoofCurrentURL: function (url) {},
     };
 }
 
+function __finishTest() {
+    if (__originalURL) {
+        internals.spoofCurrentURL(__originalURL);
+    }
+    internals.signalTextTestIsDone();
+}
+
+function spoofCurrentURL(url) {
+    if (__originalURL === null) {
+        __originalURL = document.location.href;
+    }
+    internals.spoofCurrentURL(url);
+}
+
 function println(s) {
     __outputElement.appendChild(document.createTextNode(s + "\n"));
 }
@@ -46,14 +62,14 @@ function test(f) {
     __preventMultipleTestFunctions();
     document.addEventListener("DOMContentLoaded", f);
     window.addEventListener("load", () => {
-        internals.signalTextTestIsDone();
+        __finishTest();
     });
 }
 
 function asyncTest(f) {
     const done = () => {
         __preventMultipleTestFunctions();
-        internals.signalTextTestIsDone();
+        __finishTest();
     };
     document.addEventListener("DOMContentLoaded", () => {
         f(done);
@@ -64,7 +80,7 @@ function promiseTest(f) {
     document.addEventListener("DOMContentLoaded", () => {
         f().then(() => {
             __preventMultipleTestFunctions();
-            internals.signalTextTestIsDone();
+            __finishTest();
         });
     });
 }