try/catch, but it's suboptimal; see web-platform-tests/wpt#2830 (comment)

Author: domenic

test/web-platform.js

@@ -36,7 +36,13 @@ function testURL(expected) {
 function testSetterCase(testCase, propertyName) {
   return () => {
     const url = new URL(testCase.href);
-    url[propertyName] = testCase.new_value;
+    try {
+      url[propertyName] = testCase.new_value;
+    } catch (e) {
+      if (!(e instanceof TypeError)) {
+        throw e;
+      }
+    }
 
     for (const expectedProperty in testCase.expected) {
       assert.equal(url[expectedProperty], testCase.expected[expectedProperty]);