diff --git a/test/parallel/test-whatwg-url-domainto.js b/test/parallel/test-whatwg-url-custom-domainto.js
similarity index 94%
rename from test/parallel/test-whatwg-url-domainto.js
rename to test/parallel/test-whatwg-url-custom-domainto.js
index fae9f800c79ae8..556a3ff8410b73 100644
--- a/test/parallel/test-whatwg-url-domainto.js
+++ b/test/parallel/test-whatwg-url-custom-domainto.js
@@ -1,4 +1,7 @@
 'use strict';
+
+// Tests below are not from WPT.
+
 const common = require('../common');
 
 if (!common.hasIntl)
@@ -7,9 +10,8 @@ if (!common.hasIntl)
 const assert = require('assert');
 const { domainToASCII, domainToUnicode } = require('url');
 
-// Tests below are not from WPT.
-const tests = require('../fixtures/url-idna.js');
-const wptToASCIITests = require('../fixtures/url-toascii.js');
+const tests = require('../fixtures/url-idna');
+const wptToASCIITests = require('../fixtures/url-toascii');
 
 {
   const expectedError = common.expectsError(
diff --git a/test/parallel/test-whatwg-url-global.js b/test/parallel/test-whatwg-url-custom-global.js
similarity index 93%
rename from test/parallel/test-whatwg-url-global.js
rename to test/parallel/test-whatwg-url-custom-global.js
index b4e85a49ad6343..c79723f0490e07 100644
--- a/test/parallel/test-whatwg-url-global.js
+++ b/test/parallel/test-whatwg-url-custom-global.js
@@ -1,5 +1,7 @@
 'use strict';
 
+// Tests below are not from WPT.
+
 require('../common');
 const assert = require('assert');
 const { URL, URLSearchParams } = require('url');
diff --git a/test/parallel/test-whatwg-url-inspect.js b/test/parallel/test-whatwg-url-custom-inspect.js
similarity index 99%
rename from test/parallel/test-whatwg-url-inspect.js
rename to test/parallel/test-whatwg-url-custom-inspect.js
index 1265428d4ca811..1083866d86f505 100644
--- a/test/parallel/test-whatwg-url-inspect.js
+++ b/test/parallel/test-whatwg-url-custom-inspect.js
@@ -1,5 +1,7 @@
 'use strict';
 
+// Tests below are not from WPT.
+
 const common = require('../common');
 if (!common.hasIntl) {
   // A handful of the tests fail when ICU is not included.
@@ -10,7 +12,6 @@ const util = require('util');
 const URL = require('url').URL;
 const assert = require('assert');
 
-// Tests below are not from WPT.
 const url = new URL('https://username:password@host.name:8080/path/name/?que=ry#hash');
 
 assert.strictEqual(
diff --git a/test/parallel/test-whatwg-url-parsing.js b/test/parallel/test-whatwg-url-custom-parsing.js
similarity index 99%
rename from test/parallel/test-whatwg-url-parsing.js
rename to test/parallel/test-whatwg-url-custom-parsing.js
index fd8570eb720831..252e35c8d3552c 100644
--- a/test/parallel/test-whatwg-url-parsing.js
+++ b/test/parallel/test-whatwg-url-custom-parsing.js
@@ -1,5 +1,7 @@
 'use strict';
 
+// Tests below are not from WPT.
+
 const common = require('../common');
 if (!common.hasIntl) {
   // A handful of the tests fail when ICU is not included.
@@ -10,7 +12,6 @@ const URL = require('url').URL;
 const assert = require('assert');
 const fixtures = require('../common/fixtures');
 
-// Tests below are not from WPT.
 const tests = require(fixtures.path('url-tests'));
 
 const originalFailures = tests.filter((test) => test.failure);
diff --git a/test/parallel/test-whatwg-url-properties.js b/test/parallel/test-whatwg-url-custom-properties.js
similarity index 99%
rename from test/parallel/test-whatwg-url-properties.js
rename to test/parallel/test-whatwg-url-custom-properties.js
index 230315a70efdfc..4a35215bc4ac96 100644
--- a/test/parallel/test-whatwg-url-properties.js
+++ b/test/parallel/test-whatwg-url-custom-properties.js
@@ -1,12 +1,13 @@
 // Flags: --expose-internals
 'use strict';
 
+// Tests below are not from WPT.
+
 require('../common');
 const URL = require('url').URL;
 const assert = require('assert');
 const urlToOptions = require('internal/url').urlToOptions;
 
-// Tests below are not from WPT.
 const url = new URL('http://user:pass@foo.bar.com:21/aaa/zzz?l=24#test');
 const oldParams = url.searchParams;  // for test of [SameObject]
 
diff --git a/test/parallel/test-whatwg-url-custom-searchparams-append.js b/test/parallel/test-whatwg-url-custom-searchparams-append.js
new file mode 100644
index 00000000000000..e5d3f203588c60
--- /dev/null
+++ b/test/parallel/test-whatwg-url-custom-searchparams-append.js
@@ -0,0 +1,37 @@
+'use strict';
+
+// Tests below are not from WPT.
+
+const common = require('../common');
+const assert = require('assert');
+const URLSearchParams = require('url').URLSearchParams;
+
+{
+  const params = new URLSearchParams();
+  common.expectsError(() => {
+    params.append.call(undefined);
+  }, {
+    code: 'ERR_INVALID_THIS',
+    type: TypeError,
+    message: 'Value of "this" must be of type URLSearchParams'
+  });
+  common.expectsError(() => {
+    params.append('a');
+  }, {
+    code: 'ERR_MISSING_ARGS',
+    type: TypeError,
+    message: 'The "name" and "value" arguments must be specified'
+  });
+
+  const obj = {
+    toString() { throw new Error('toString'); },
+    valueOf() { throw new Error('valueOf'); }
+  };
+  const sym = Symbol();
+  assert.throws(() => params.set(obj, 'b'), /^Error: toString$/);
+  assert.throws(() => params.set('a', obj), /^Error: toString$/);
+  assert.throws(() => params.set(sym, 'b'),
+                /^TypeError: Cannot convert a Symbol value to a string$/);
+  assert.throws(() => params.set('a', sym),
+                /^TypeError: Cannot convert a Symbol value to a string$/);
+}
diff --git a/test/parallel/test-whatwg-url-custom-searchparams-constructor.js b/test/parallel/test-whatwg-url-custom-searchparams-constructor.js
new file mode 100644
index 00000000000000..fd7cc511279033
--- /dev/null
+++ b/test/parallel/test-whatwg-url-custom-searchparams-constructor.js
@@ -0,0 +1,69 @@
+'use strict';
+
+// Tests below are not from WPT.
+
+const common = require('../common');
+const assert = require('assert');
+const URLSearchParams = require('url').URLSearchParams;
+
+function makeIterableFunc(array) {
+  return Object.assign(() => {}, {
+    [Symbol.iterator]() {
+      return array[Symbol.iterator]();
+    }
+  });
+}
+
+{
+  const iterableError = common.expectsError({
+    code: 'ERR_ARG_NOT_ITERABLE',
+    type: TypeError,
+    message: 'Query pairs must be iterable'
+  });
+  const tupleError = common.expectsError({
+    code: 'ERR_INVALID_TUPLE',
+    type: TypeError,
+    message: 'Each query pair must be an iterable [name, value] tuple'
+  }, 6);
+
+  let params;
+  params = new URLSearchParams(undefined);
+  assert.strictEqual(params.toString(), '');
+  params = new URLSearchParams(null);
+  assert.strictEqual(params.toString(), '');
+  params = new URLSearchParams(
+    makeIterableFunc([['key', 'val'], ['key2', 'val2']])
+  );
+  assert.strictEqual(params.toString(), 'key=val&key2=val2');
+  params = new URLSearchParams(
+    makeIterableFunc([['key', 'val'], ['key2', 'val2']].map(makeIterableFunc))
+  );
+  assert.strictEqual(params.toString(), 'key=val&key2=val2');
+  assert.throws(() => new URLSearchParams([[1]]), tupleError);
+  assert.throws(() => new URLSearchParams([[1, 2, 3]]), tupleError);
+  assert.throws(() => new URLSearchParams({ [Symbol.iterator]: 42 }),
+                iterableError);
+  assert.throws(() => new URLSearchParams([{}]), tupleError);
+  assert.throws(() => new URLSearchParams(['a']), tupleError);
+  assert.throws(() => new URLSearchParams([null]), tupleError);
+  assert.throws(() => new URLSearchParams([{ [Symbol.iterator]: 42 }]),
+                tupleError);
+}
+
+{
+  const obj = {
+    toString() { throw new Error('toString'); },
+    valueOf() { throw new Error('valueOf'); }
+  };
+  const sym = Symbol();
+  const toStringError = /^Error: toString$/;
+  const symbolError = /^TypeError: Cannot convert a Symbol value to a string$/;
+
+  assert.throws(() => new URLSearchParams({ a: obj }), toStringError);
+  assert.throws(() => new URLSearchParams([['a', obj]]), toStringError);
+  assert.throws(() => new URLSearchParams(sym), symbolError);
+  assert.throws(() => new URLSearchParams({ [sym]: 'a' }), symbolError);
+  assert.throws(() => new URLSearchParams({ a: sym }), symbolError);
+  assert.throws(() => new URLSearchParams([[sym, 'a']]), symbolError);
+  assert.throws(() => new URLSearchParams([['a', sym]]), symbolError);
+}
diff --git a/test/parallel/test-whatwg-url-custom-searchparams-delete.js b/test/parallel/test-whatwg-url-custom-searchparams-delete.js
new file mode 100644
index 00000000000000..a22345cc6eef82
--- /dev/null
+++ b/test/parallel/test-whatwg-url-custom-searchparams-delete.js
@@ -0,0 +1,46 @@
+'use strict';
+
+// Tests below are not from WPT.
+
+const common = require('../common');
+const assert = require('assert');
+const { URL, URLSearchParams } = require('url');
+
+{
+  const params = new URLSearchParams();
+  common.expectsError(() => {
+    params.delete.call(undefined);
+  }, {
+    code: 'ERR_INVALID_THIS',
+    type: TypeError,
+    message: 'Value of "this" must be of type URLSearchParams'
+  });
+  common.expectsError(() => {
+    params.delete();
+  }, {
+    code: 'ERR_MISSING_ARGS',
+    type: TypeError,
+    message: 'The "name" argument must be specified'
+  });
+
+  const obj = {
+    toString() { throw new Error('toString'); },
+    valueOf() { throw new Error('valueOf'); }
+  };
+  const sym = Symbol();
+  assert.throws(() => params.delete(obj), /^Error: toString$/);
+  assert.throws(() => params.delete(sym),
+                /^TypeError: Cannot convert a Symbol value to a string$/);
+}
+
+// https://github.com/nodejs/node/issues/10480
+// Emptying searchParams should correctly update url's query
+{
+  const url = new URL('http://domain?var=1&var=2&var=3');
+  for (const param of url.searchParams.keys()) {
+    url.searchParams.delete(param);
+  }
+  assert.strictEqual(url.searchParams.toString(), '');
+  assert.strictEqual(url.search, '');
+  assert.strictEqual(url.href, 'http://domain/');
+}
diff --git a/test/parallel/test-whatwg-url-searchparams-entries.js b/test/parallel/test-whatwg-url-custom-searchparams-entries.js
similarity index 100%
rename from test/parallel/test-whatwg-url-searchparams-entries.js
rename to test/parallel/test-whatwg-url-custom-searchparams-entries.js
diff --git a/test/parallel/test-whatwg-url-custom-searchparams-foreach.js b/test/parallel/test-whatwg-url-custom-searchparams-foreach.js
new file mode 100644
index 00000000000000..3e729d2bcd4cdd
--- /dev/null
+++ b/test/parallel/test-whatwg-url-custom-searchparams-foreach.js
@@ -0,0 +1,17 @@
+'use strict';
+
+// Tests below are not from WPT.
+
+const common = require('../common');
+const { URLSearchParams } = require('url');
+
+{
+  const params = new URLSearchParams();
+  common.expectsError(() => {
+    params.forEach.call(undefined);
+  }, {
+    code: 'ERR_INVALID_THIS',
+    type: TypeError,
+    message: 'Value of "this" must be of type URLSearchParams'
+  });
+}
diff --git a/test/parallel/test-whatwg-url-custom-searchparams-get.js b/test/parallel/test-whatwg-url-custom-searchparams-get.js
new file mode 100644
index 00000000000000..b99a5fae97d927
--- /dev/null
+++ b/test/parallel/test-whatwg-url-custom-searchparams-get.js
@@ -0,0 +1,34 @@
+'use strict';
+
+// Tests below are not from WPT.
+
+const common = require('../common');
+const assert = require('assert');
+const URLSearchParams = require('url').URLSearchParams;
+
+{
+  const params = new URLSearchParams();
+  common.expectsError(() => {
+    params.get.call(undefined);
+  }, {
+    code: 'ERR_INVALID_THIS',
+    type: TypeError,
+    message: 'Value of "this" must be of type URLSearchParams'
+  });
+  common.expectsError(() => {
+    params.get();
+  }, {
+    code: 'ERR_MISSING_ARGS',
+    type: TypeError,
+    message: 'The "name" argument must be specified'
+  });
+
+  const obj = {
+    toString() { throw new Error('toString'); },
+    valueOf() { throw new Error('valueOf'); }
+  };
+  const sym = Symbol();
+  assert.throws(() => params.get(obj), /^Error: toString$/);
+  assert.throws(() => params.get(sym),
+                /^TypeError: Cannot convert a Symbol value to a string$/);
+}
diff --git a/test/parallel/test-whatwg-url-custom-searchparams-getall.js b/test/parallel/test-whatwg-url-custom-searchparams-getall.js
new file mode 100644
index 00000000000000..7f3c7b7610cfd7
--- /dev/null
+++ b/test/parallel/test-whatwg-url-custom-searchparams-getall.js
@@ -0,0 +1,34 @@
+'use strict';
+
+// Tests below are not from WPT.
+
+const common = require('../common');
+const assert = require('assert');
+const URLSearchParams = require('url').URLSearchParams;
+
+{
+  const params = new URLSearchParams();
+  common.expectsError(() => {
+    params.getAll.call(undefined);
+  }, {
+    code: 'ERR_INVALID_THIS',
+    type: TypeError,
+    message: 'Value of "this" must be of type URLSearchParams'
+  });
+  common.expectsError(() => {
+    params.getAll();
+  }, {
+    code: 'ERR_MISSING_ARGS',
+    type: TypeError,
+    message: 'The "name" argument must be specified'
+  });
+
+  const obj = {
+    toString() { throw new Error('toString'); },
+    valueOf() { throw new Error('valueOf'); }
+  };
+  const sym = Symbol();
+  assert.throws(() => params.getAll(obj), /^Error: toString$/);
+  assert.throws(() => params.getAll(sym),
+                /^TypeError: Cannot convert a Symbol value to a string$/);
+}
diff --git a/test/parallel/test-whatwg-url-custom-searchparams-has.js b/test/parallel/test-whatwg-url-custom-searchparams-has.js
new file mode 100644
index 00000000000000..2697f199bcc98b
--- /dev/null
+++ b/test/parallel/test-whatwg-url-custom-searchparams-has.js
@@ -0,0 +1,34 @@
+'use strict';
+
+// Tests below are not from WPT.
+
+const common = require('../common');
+const assert = require('assert');
+const URLSearchParams = require('url').URLSearchParams;
+
+{
+  const params = new URLSearchParams();
+  common.expectsError(() => {
+    params.has.call(undefined);
+  }, {
+    code: 'ERR_INVALID_THIS',
+    type: TypeError,
+    message: 'Value of "this" must be of type URLSearchParams'
+  });
+  common.expectsError(() => {
+    params.has();
+  }, {
+    code: 'ERR_MISSING_ARGS',
+    type: TypeError,
+    message: 'The "name" argument must be specified'
+  });
+
+  const obj = {
+    toString() { throw new Error('toString'); },
+    valueOf() { throw new Error('valueOf'); }
+  };
+  const sym = Symbol();
+  assert.throws(() => params.has(obj), /^Error: toString$/);
+  assert.throws(() => params.has(sym),
+                /^TypeError: Cannot convert a Symbol value to a string$/);
+}
diff --git a/test/parallel/test-whatwg-url-searchparams-inspect.js b/test/parallel/test-whatwg-url-custom-searchparams-inspect.js
similarity index 99%
rename from test/parallel/test-whatwg-url-searchparams-inspect.js
rename to test/parallel/test-whatwg-url-custom-searchparams-inspect.js
index f2493cc6cff176..6cc22caea62436 100644
--- a/test/parallel/test-whatwg-url-searchparams-inspect.js
+++ b/test/parallel/test-whatwg-url-custom-searchparams-inspect.js
@@ -1,11 +1,12 @@
 'use strict';
 
+// Tests below are not from WPT.
+
 require('../common');
 const assert = require('assert');
 const util = require('util');
 const URLSearchParams = require('url').URLSearchParams;
 
-// Tests below are not from WPT.
 const sp = new URLSearchParams('?a=a&b=b&b=c');
 assert.strictEqual(util.inspect(sp),
                    "URLSearchParams { 'a' => 'a', 'b' => 'b', 'b' => 'c' }");
diff --git a/test/parallel/test-whatwg-url-searchparams-keys.js b/test/parallel/test-whatwg-url-custom-searchparams-keys.js
similarity index 99%
rename from test/parallel/test-whatwg-url-searchparams-keys.js
rename to test/parallel/test-whatwg-url-custom-searchparams-keys.js
index e4428eb3e98f6b..00800cc79cbf7e 100644
--- a/test/parallel/test-whatwg-url-searchparams-keys.js
+++ b/test/parallel/test-whatwg-url-custom-searchparams-keys.js
@@ -1,10 +1,11 @@
 'use strict';
 
+// Tests below are not from WPT.
+
 const common = require('../common');
 const assert = require('assert');
 const URLSearchParams = require('url').URLSearchParams;
 
-// Tests below are not from WPT.
 const params = new URLSearchParams('a=b&c=d');
 const keys = params.keys();
 
diff --git a/test/parallel/test-whatwg-url-custom-searchparams-set.js b/test/parallel/test-whatwg-url-custom-searchparams-set.js
new file mode 100644
index 00000000000000..ccd3353ecd0e8e
--- /dev/null
+++ b/test/parallel/test-whatwg-url-custom-searchparams-set.js
@@ -0,0 +1,37 @@
+'use strict';
+
+// Tests below are not from WPT.
+
+const common = require('../common');
+const assert = require('assert');
+const URLSearchParams = require('url').URLSearchParams;
+
+{
+  const params = new URLSearchParams();
+  common.expectsError(() => {
+    params.set.call(undefined);
+  }, {
+    code: 'ERR_INVALID_THIS',
+    type: TypeError,
+    message: 'Value of "this" must be of type URLSearchParams'
+  });
+  common.expectsError(() => {
+    params.set('a');
+  }, {
+    code: 'ERR_MISSING_ARGS',
+    type: TypeError,
+    message: 'The "name" and "value" arguments must be specified'
+  });
+
+  const obj = {
+    toString() { throw new Error('toString'); },
+    valueOf() { throw new Error('valueOf'); }
+  };
+  const sym = Symbol();
+  assert.throws(() => params.append(obj, 'b'), /^Error: toString$/);
+  assert.throws(() => params.append('a', obj), /^Error: toString$/);
+  assert.throws(() => params.append(sym, 'b'),
+                /^TypeError: Cannot convert a Symbol value to a string$/);
+  assert.throws(() => params.append('a', sym),
+                /^TypeError: Cannot convert a Symbol value to a string$/);
+}
diff --git a/test/parallel/test-whatwg-url-custom-searchparams-sort.js b/test/parallel/test-whatwg-url-custom-searchparams-sort.js
new file mode 100644
index 00000000000000..f8884a7e7092a3
--- /dev/null
+++ b/test/parallel/test-whatwg-url-custom-searchparams-sort.js
@@ -0,0 +1,47 @@
+'use strict';
+
+// Tests below are not from WPT.
+
+require('../common');
+const { URL, URLSearchParams } = require('url');
+const { test, assert_array_equals } = require('../common/wpt');
+
+// Test bottom-up iterative stable merge sort
+const tests = [{ input: '', output: [] }];
+const pairs = [];
+for (let i = 10; i < 100; i++) {
+  pairs.push([`a${i}`, 'b']);
+  tests[0].output.push([`a${i}`, 'b']);
+}
+tests[0].input = pairs.sort(() => Math.random() > 0.5)
+  .map((pair) => pair.join('=')).join('&');
+
+tests.push(
+  {
+    'input': 'z=a&=b&c=d',
+    'output': [['', 'b'], ['c', 'd'], ['z', 'a']]
+  }
+);
+
+tests.forEach((val) => {
+  test(() => {
+    const params = new URLSearchParams(val.input);
+    let i = 0;
+    params.sort();
+    for (const param of params) {
+      assert_array_equals(param, val.output[i]);
+      i++;
+    }
+  }, `Parse and sort: ${val.input}`);
+
+  test(() => {
+    const url = new URL(`?${val.input}`, 'https://example/');
+    url.searchParams.sort();
+    const params = new URLSearchParams(url.search);
+    let i = 0;
+    for (const param of params) {
+      assert_array_equals(param, val.output[i]);
+      i++;
+    }
+  }, `URL parse and sort: ${val.input}`);
+});
diff --git a/test/parallel/test-whatwg-url-custom-searchparams-stringifier.js b/test/parallel/test-whatwg-url-custom-searchparams-stringifier.js
new file mode 100644
index 00000000000000..d2929ae557a079
--- /dev/null
+++ b/test/parallel/test-whatwg-url-custom-searchparams-stringifier.js
@@ -0,0 +1,17 @@
+'use strict';
+
+// Tests below are not from WPT.
+
+const common = require('../common');
+const URLSearchParams = require('url').URLSearchParams;
+
+{
+  const params = new URLSearchParams();
+  common.expectsError(() => {
+    params.toString.call(undefined);
+  }, {
+    code: 'ERR_INVALID_THIS',
+    type: TypeError,
+    message: 'Value of "this" must be of type URLSearchParams'
+  });
+}
diff --git a/test/parallel/test-whatwg-url-searchparams-values.js b/test/parallel/test-whatwg-url-custom-searchparams-values.js
similarity index 99%
rename from test/parallel/test-whatwg-url-searchparams-values.js
rename to test/parallel/test-whatwg-url-custom-searchparams-values.js
index e44b7f5e11267d..e10a9dc04fe0df 100644
--- a/test/parallel/test-whatwg-url-searchparams-values.js
+++ b/test/parallel/test-whatwg-url-custom-searchparams-values.js
@@ -1,10 +1,11 @@
 'use strict';
 
+// Tests below are not from WPT.
+
 const common = require('../common');
 const assert = require('assert');
 const URLSearchParams = require('url').URLSearchParams;
 
-// Tests below are not from WPT.
 const params = new URLSearchParams('a=b&c=d');
 const values = params.values();
 
diff --git a/test/parallel/test-whatwg-url-searchparams.js b/test/parallel/test-whatwg-url-custom-searchparams.js
similarity index 99%
rename from test/parallel/test-whatwg-url-searchparams.js
rename to test/parallel/test-whatwg-url-custom-searchparams.js
index 0b72c08d0b887f..f88c3b4a836b39 100644
--- a/test/parallel/test-whatwg-url-searchparams.js
+++ b/test/parallel/test-whatwg-url-custom-searchparams.js
@@ -1,11 +1,12 @@
 'use strict';
 
+// Tests below are not from WPT.
+
 const common = require('../common');
 const assert = require('assert');
 const { URL, URLSearchParams } = require('url');
 const fixtures = require('../common/fixtures');
 
-// Tests below are not from WPT.
 const serialized = 'a=a&a=1&a=true&a=undefined&a=null&a=%EF%BF%BD' +
                    '&a=%EF%BF%BD&a=%F0%9F%98%80&a=%EF%BF%BD%EF%BF%BD' +
                    '&a=%5Bobject+Object%5D';
diff --git a/test/parallel/test-whatwg-url-custom-setters.js b/test/parallel/test-whatwg-url-custom-setters.js
new file mode 100644
index 00000000000000..99b4361831fd3b
--- /dev/null
+++ b/test/parallel/test-whatwg-url-custom-setters.js
@@ -0,0 +1,60 @@
+'use strict';
+
+// Tests below are not from WPT.
+
+const common = require('../common');
+if (!common.hasIntl) {
+  // A handful of the tests fail when ICU is not included.
+  common.skip('missing Intl');
+}
+
+const assert = require('assert');
+const URL = require('url').URL;
+const { test, assert_equals } = require('../common/wpt');
+const fixtures = require('../common/fixtures');
+
+const additionalTestCases =
+  require(fixtures.path('url-setter-tests-additional.js'));
+
+{
+  for (const attributeToBeSet in additionalTestCases) {
+    if (attributeToBeSet === 'comment') {
+      continue;
+    }
+    const testCases = additionalTestCases[attributeToBeSet];
+    for (const testCase of testCases) {
+      let name = `Setting <${testCase.href}>.${attributeToBeSet}` +
+                 ` = "${testCase.new_value}"`;
+      if ('comment' in testCase) {
+        name += ` ${testCase.comment}`;
+      }
+      test(function() {
+        const url = new URL(testCase.href);
+        url[attributeToBeSet] = testCase.new_value;
+        for (const attribute in testCase.expected) {
+          assert_equals(url[attribute], testCase.expected[attribute]);
+        }
+      }, `URL: ${name}`);
+    }
+  }
+}
+
+{
+  const url = new URL('http://example.com/');
+  const obj = {
+    toString() { throw new Error('toString'); },
+    valueOf() { throw new Error('valueOf'); }
+  };
+  const sym = Symbol();
+  const props = Object.getOwnPropertyDescriptors(Object.getPrototypeOf(url));
+  for (const [name, { set }] of Object.entries(props)) {
+    if (set) {
+      assert.throws(() => url[name] = obj,
+                    /^Error: toString$/,
+                    `url.${name} = { toString() { throw ... } }`);
+      assert.throws(() => url[name] = sym,
+                    /^TypeError: Cannot convert a Symbol value to a string$/,
+                    `url.${name} = ${String(sym)}`);
+    }
+  }
+}
diff --git a/test/parallel/test-whatwg-url-tostringtag.js b/test/parallel/test-whatwg-url-custom-tostringtag.js
similarity index 99%
rename from test/parallel/test-whatwg-url-tostringtag.js
rename to test/parallel/test-whatwg-url-custom-tostringtag.js
index c352503fa09a66..784a3ebc7728e5 100644
--- a/test/parallel/test-whatwg-url-tostringtag.js
+++ b/test/parallel/test-whatwg-url-custom-tostringtag.js
@@ -1,10 +1,11 @@
 'use strict';
 
+// Tests below are not from WPT.
+
 require('../common');
 const assert = require('assert');
 const URL = require('url').URL;
 
-// Tests below are not from WPT.
 const toString = Object.prototype.toString;
 
 const url = new URL('http://example.org');
diff --git a/test/parallel/test-whatwg-url-searchparams-append.js b/test/parallel/test-whatwg-url-searchparams-append.js
index 03e7205fb2cb51..342cbd53357986 100644
--- a/test/parallel/test-whatwg-url-searchparams-append.js
+++ b/test/parallel/test-whatwg-url-searchparams-append.js
@@ -1,7 +1,6 @@
 'use strict';
 
-const common = require('../common');
-const assert = require('assert');
+require('../common');
 const URLSearchParams = require('url').URLSearchParams;
 const { test, assert_equals, assert_true } = require('../common/wpt');
 
@@ -48,34 +47,3 @@ test(function() {
     assert_equals(params.get('first'), '1', 'Search params object has name "first" with value "1"');
 }, 'Append multiple');
 /* eslint-enable */
-
-// Tests below are not from WPT.
-{
-  const params = new URLSearchParams();
-  common.expectsError(() => {
-    params.append.call(undefined);
-  }, {
-    code: 'ERR_INVALID_THIS',
-    type: TypeError,
-    message: 'Value of "this" must be of type URLSearchParams'
-  });
-  common.expectsError(() => {
-    params.append('a');
-  }, {
-    code: 'ERR_MISSING_ARGS',
-    type: TypeError,
-    message: 'The "name" and "value" arguments must be specified'
-  });
-
-  const obj = {
-    toString() { throw new Error('toString'); },
-    valueOf() { throw new Error('valueOf'); }
-  };
-  const sym = Symbol();
-  assert.throws(() => params.set(obj, 'b'), /^Error: toString$/);
-  assert.throws(() => params.set('a', obj), /^Error: toString$/);
-  assert.throws(() => params.set(sym, 'b'),
-                /^TypeError: Cannot convert a Symbol value to a string$/);
-  assert.throws(() => params.set('a', sym),
-                /^TypeError: Cannot convert a Symbol value to a string$/);
-}
diff --git a/test/parallel/test-whatwg-url-searchparams-constructor.js b/test/parallel/test-whatwg-url-searchparams-constructor.js
index b6e720cc7fb04c..882072ba445fcb 100644
--- a/test/parallel/test-whatwg-url-searchparams-constructor.js
+++ b/test/parallel/test-whatwg-url-searchparams-constructor.js
@@ -1,7 +1,6 @@
 'use strict';
 
-const common = require('../common');
-const assert = require('assert');
+require('../common');
 const URLSearchParams = require('url').URLSearchParams;
 const {
   test, assert_equals, assert_true,
@@ -190,66 +189,3 @@ test(() => {
   assert_equals(params2.get("a"), "b")
 }, "Custom [Symbol.iterator]")
 /* eslint-enable */
-
-// Tests below are not from WPT.
-function makeIterableFunc(array) {
-  return Object.assign(() => {}, {
-    [Symbol.iterator]() {
-      return array[Symbol.iterator]();
-    }
-  });
-}
-
-{
-  const iterableError = common.expectsError({
-    code: 'ERR_ARG_NOT_ITERABLE',
-    type: TypeError,
-    message: 'Query pairs must be iterable'
-  });
-  const tupleError = common.expectsError({
-    code: 'ERR_INVALID_TUPLE',
-    type: TypeError,
-    message: 'Each query pair must be an iterable [name, value] tuple'
-  }, 6);
-
-  let params;
-  params = new URLSearchParams(undefined);
-  assert.strictEqual(params.toString(), '');
-  params = new URLSearchParams(null);
-  assert.strictEqual(params.toString(), '');
-  params = new URLSearchParams(
-    makeIterableFunc([['key', 'val'], ['key2', 'val2']])
-  );
-  assert.strictEqual(params.toString(), 'key=val&key2=val2');
-  params = new URLSearchParams(
-    makeIterableFunc([['key', 'val'], ['key2', 'val2']].map(makeIterableFunc))
-  );
-  assert.strictEqual(params.toString(), 'key=val&key2=val2');
-  assert.throws(() => new URLSearchParams([[1]]), tupleError);
-  assert.throws(() => new URLSearchParams([[1, 2, 3]]), tupleError);
-  assert.throws(() => new URLSearchParams({ [Symbol.iterator]: 42 }),
-                iterableError);
-  assert.throws(() => new URLSearchParams([{}]), tupleError);
-  assert.throws(() => new URLSearchParams(['a']), tupleError);
-  assert.throws(() => new URLSearchParams([null]), tupleError);
-  assert.throws(() => new URLSearchParams([{ [Symbol.iterator]: 42 }]),
-                tupleError);
-}
-
-{
-  const obj = {
-    toString() { throw new Error('toString'); },
-    valueOf() { throw new Error('valueOf'); }
-  };
-  const sym = Symbol();
-  const toStringError = /^Error: toString$/;
-  const symbolError = /^TypeError: Cannot convert a Symbol value to a string$/;
-
-  assert.throws(() => new URLSearchParams({ a: obj }), toStringError);
-  assert.throws(() => new URLSearchParams([['a', obj]]), toStringError);
-  assert.throws(() => new URLSearchParams(sym), symbolError);
-  assert.throws(() => new URLSearchParams({ [sym]: 'a' }), symbolError);
-  assert.throws(() => new URLSearchParams({ a: sym }), symbolError);
-  assert.throws(() => new URLSearchParams([[sym, 'a']]), symbolError);
-  assert.throws(() => new URLSearchParams([['a', sym]]), symbolError);
-}
diff --git a/test/parallel/test-whatwg-url-searchparams-delete.js b/test/parallel/test-whatwg-url-searchparams-delete.js
index 042ecb5d889beb..cdf3332efc7807 100644
--- a/test/parallel/test-whatwg-url-searchparams-delete.js
+++ b/test/parallel/test-whatwg-url-searchparams-delete.js
@@ -1,7 +1,6 @@
 'use strict';
 
-const common = require('../common');
-const assert = require('assert');
+require('../common');
 const { URL, URLSearchParams } = require('url');
 const { test, assert_equals, assert_true, assert_false } =
   require('../common/wpt');
@@ -58,43 +57,3 @@ test(function() {
     assert_equals(url.search, '', 'url.search does not have ?');
 }, 'Removing non-existent param removes ? from URL');
 /* eslint-enable */
-
-// Tests below are not from WPT.
-{
-  const params = new URLSearchParams();
-  common.expectsError(() => {
-    params.delete.call(undefined);
-  }, {
-    code: 'ERR_INVALID_THIS',
-    type: TypeError,
-    message: 'Value of "this" must be of type URLSearchParams'
-  });
-  common.expectsError(() => {
-    params.delete();
-  }, {
-    code: 'ERR_MISSING_ARGS',
-    type: TypeError,
-    message: 'The "name" argument must be specified'
-  });
-
-  const obj = {
-    toString() { throw new Error('toString'); },
-    valueOf() { throw new Error('valueOf'); }
-  };
-  const sym = Symbol();
-  assert.throws(() => params.delete(obj), /^Error: toString$/);
-  assert.throws(() => params.delete(sym),
-                /^TypeError: Cannot convert a Symbol value to a string$/);
-}
-
-// https://github.com/nodejs/node/issues/10480
-// Emptying searchParams should correctly update url's query
-{
-  const url = new URL('http://domain?var=1&var=2&var=3');
-  for (const param of url.searchParams.keys()) {
-    url.searchParams.delete(param);
-  }
-  assert.strictEqual(url.searchParams.toString(), '');
-  assert.strictEqual(url.search, '');
-  assert.strictEqual(url.href, 'http://domain/');
-}
diff --git a/test/parallel/test-whatwg-url-searchparams-foreach.js b/test/parallel/test-whatwg-url-searchparams-foreach.js
index 53c35da263f5ab..833858618f8e5b 100644
--- a/test/parallel/test-whatwg-url-searchparams-foreach.js
+++ b/test/parallel/test-whatwg-url-searchparams-foreach.js
@@ -1,6 +1,6 @@
 'use strict';
 
-const common = require('../common');
+require('../common');
 const { URL, URLSearchParams } = require('url');
 const { test, assert_array_equals, assert_unreached } =
   require('../common/wpt');
@@ -45,15 +45,3 @@ test(function() {
     }
 }, "empty");
 /* eslint-enable */
-
-// Tests below are not from WPT.
-{
-  const params = new URLSearchParams();
-  common.expectsError(() => {
-    params.forEach.call(undefined);
-  }, {
-    code: 'ERR_INVALID_THIS',
-    type: TypeError,
-    message: 'Value of "this" must be of type URLSearchParams'
-  });
-}
diff --git a/test/parallel/test-whatwg-url-searchparams-get.js b/test/parallel/test-whatwg-url-searchparams-get.js
index e14bdc7e74fc8d..94e92c18e4b218 100644
--- a/test/parallel/test-whatwg-url-searchparams-get.js
+++ b/test/parallel/test-whatwg-url-searchparams-get.js
@@ -1,7 +1,6 @@
 'use strict';
 
-const common = require('../common');
-const assert = require('assert');
+require('../common');
 const URLSearchParams = require('url').URLSearchParams;
 const { test, assert_equals, assert_true } = require('../common/wpt');
 
@@ -33,31 +32,3 @@ test(function() {
     assert_equals(params.get('fourth'), null, 'Search params object has no "fourth" name and value.');
 }, 'More get() basics');
 /* eslint-enable */
-
-// Tests below are not from WPT.
-{
-  const params = new URLSearchParams();
-  common.expectsError(() => {
-    params.get.call(undefined);
-  }, {
-    code: 'ERR_INVALID_THIS',
-    type: TypeError,
-    message: 'Value of "this" must be of type URLSearchParams'
-  });
-  common.expectsError(() => {
-    params.get();
-  }, {
-    code: 'ERR_MISSING_ARGS',
-    type: TypeError,
-    message: 'The "name" argument must be specified'
-  });
-
-  const obj = {
-    toString() { throw new Error('toString'); },
-    valueOf() { throw new Error('valueOf'); }
-  };
-  const sym = Symbol();
-  assert.throws(() => params.get(obj), /^Error: toString$/);
-  assert.throws(() => params.get(sym),
-                /^TypeError: Cannot convert a Symbol value to a string$/);
-}
diff --git a/test/parallel/test-whatwg-url-searchparams-getall.js b/test/parallel/test-whatwg-url-searchparams-getall.js
index a4692c22f1b21d..06827f37d95bfe 100644
--- a/test/parallel/test-whatwg-url-searchparams-getall.js
+++ b/test/parallel/test-whatwg-url-searchparams-getall.js
@@ -1,7 +1,6 @@
 'use strict';
 
-const common = require('../common');
-const assert = require('assert');
+require('../common');
 const URLSearchParams = require('url').URLSearchParams;
 const { test, assert_equals, assert_true, assert_array_equals } =
   require('../common/wpt');
@@ -38,31 +37,3 @@ test(function() {
     assert_array_equals(matches, ['one'], 'Search params object has expected name "a" values');
 }, 'getAll() multiples');
 /* eslint-enable */
-
-// Tests below are not from WPT.
-{
-  const params = new URLSearchParams();
-  common.expectsError(() => {
-    params.getAll.call(undefined);
-  }, {
-    code: 'ERR_INVALID_THIS',
-    type: TypeError,
-    message: 'Value of "this" must be of type URLSearchParams'
-  });
-  common.expectsError(() => {
-    params.getAll();
-  }, {
-    code: 'ERR_MISSING_ARGS',
-    type: TypeError,
-    message: 'The "name" argument must be specified'
-  });
-
-  const obj = {
-    toString() { throw new Error('toString'); },
-    valueOf() { throw new Error('valueOf'); }
-  };
-  const sym = Symbol();
-  assert.throws(() => params.getAll(obj), /^Error: toString$/);
-  assert.throws(() => params.getAll(sym),
-                /^TypeError: Cannot convert a Symbol value to a string$/);
-}
diff --git a/test/parallel/test-whatwg-url-searchparams-has.js b/test/parallel/test-whatwg-url-searchparams-has.js
index 47c6b6f7bae98f..95e69beb4d26ec 100644
--- a/test/parallel/test-whatwg-url-searchparams-has.js
+++ b/test/parallel/test-whatwg-url-searchparams-has.js
@@ -1,7 +1,6 @@
 'use strict';
 
-const common = require('../common');
-const assert = require('assert');
+require('../common');
 const URLSearchParams = require('url').URLSearchParams;
 const { test, assert_false, assert_true } = require('../common/wpt');
 
@@ -36,31 +35,3 @@ test(function() {
     assert_false(params.has('first'), 'Search params object has no name "first"');
 }, 'has() following delete()');
 /* eslint-enable */
-
-// Tests below are not from WPT.
-{
-  const params = new URLSearchParams();
-  common.expectsError(() => {
-    params.has.call(undefined);
-  }, {
-    code: 'ERR_INVALID_THIS',
-    type: TypeError,
-    message: 'Value of "this" must be of type URLSearchParams'
-  });
-  common.expectsError(() => {
-    params.has();
-  }, {
-    code: 'ERR_MISSING_ARGS',
-    type: TypeError,
-    message: 'The "name" argument must be specified'
-  });
-
-  const obj = {
-    toString() { throw new Error('toString'); },
-    valueOf() { throw new Error('valueOf'); }
-  };
-  const sym = Symbol();
-  assert.throws(() => params.has(obj), /^Error: toString$/);
-  assert.throws(() => params.has(sym),
-                /^TypeError: Cannot convert a Symbol value to a string$/);
-}
diff --git a/test/parallel/test-whatwg-url-searchparams-set.js b/test/parallel/test-whatwg-url-searchparams-set.js
index 1bca12e31bcc28..0d43678427c23f 100644
--- a/test/parallel/test-whatwg-url-searchparams-set.js
+++ b/test/parallel/test-whatwg-url-searchparams-set.js
@@ -1,7 +1,6 @@
 'use strict';
 
-const common = require('../common');
-const assert = require('assert');
+require('../common');
 const URLSearchParams = require('url').URLSearchParams;
 const { test, assert_equals, assert_true } = require('../common/wpt');
 
@@ -34,34 +33,3 @@ test(function() {
     assert_equals(params.get('a'), '4', 'Search params object has name "a" with value "4"');
 }, 'URLSearchParams.set');
 /* eslint-enable */
-
-// Tests below are not from WPT.
-{
-  const params = new URLSearchParams();
-  common.expectsError(() => {
-    params.set.call(undefined);
-  }, {
-    code: 'ERR_INVALID_THIS',
-    type: TypeError,
-    message: 'Value of "this" must be of type URLSearchParams'
-  });
-  common.expectsError(() => {
-    params.set('a');
-  }, {
-    code: 'ERR_MISSING_ARGS',
-    type: TypeError,
-    message: 'The "name" and "value" arguments must be specified'
-  });
-
-  const obj = {
-    toString() { throw new Error('toString'); },
-    valueOf() { throw new Error('valueOf'); }
-  };
-  const sym = Symbol();
-  assert.throws(() => params.append(obj, 'b'), /^Error: toString$/);
-  assert.throws(() => params.append('a', obj), /^Error: toString$/);
-  assert.throws(() => params.append(sym, 'b'),
-                /^TypeError: Cannot convert a Symbol value to a string$/);
-  assert.throws(() => params.append('a', sym),
-                /^TypeError: Cannot convert a Symbol value to a string$/);
-}
diff --git a/test/parallel/test-whatwg-url-searchparams-sort.js b/test/parallel/test-whatwg-url-searchparams-sort.js
index 1122f08dcc0434..65dd23a6daba57 100644
--- a/test/parallel/test-whatwg-url-searchparams-sort.js
+++ b/test/parallel/test-whatwg-url-searchparams-sort.js
@@ -61,45 +61,3 @@ test(function() {
   assert_equals(url.search, "")
 }, "Sorting non-existent params removes ? from URL")
 /* eslint-enable */
-
-// Tests below are not from WPT.
-
-// Test bottom-up iterative stable merge sort
-const tests = [{ input: '', output: [] }];
-const pairs = [];
-for (let i = 10; i < 100; i++) {
-  pairs.push([`a${i}`, 'b']);
-  tests[0].output.push([`a${i}`, 'b']);
-}
-tests[0].input = pairs.sort(() => Math.random() > 0.5)
-  .map((pair) => pair.join('=')).join('&');
-
-tests.push(
-  {
-    'input': 'z=a&=b&c=d',
-    'output': [['', 'b'], ['c', 'd'], ['z', 'a']]
-  }
-);
-
-tests.forEach((val) => {
-  test(() => {
-    const params = new URLSearchParams(val.input);
-    let i = 0;
-    params.sort();
-    for (const param of params) {
-      assert_array_equals(param, val.output[i]);
-      i++;
-    }
-  }, `Parse and sort: ${val.input}`);
-
-  test(() => {
-    const url = new URL(`?${val.input}`, 'https://example/');
-    url.searchParams.sort();
-    const params = new URLSearchParams(url.search);
-    let i = 0;
-    for (const param of params) {
-      assert_array_equals(param, val.output[i]);
-      i++;
-    }
-  }, `URL parse and sort: ${val.input}`);
-});
diff --git a/test/parallel/test-whatwg-url-searchparams-stringifier.js b/test/parallel/test-whatwg-url-searchparams-stringifier.js
index e3bfbdcf1982d8..e2b6faaabe85fc 100644
--- a/test/parallel/test-whatwg-url-searchparams-stringifier.js
+++ b/test/parallel/test-whatwg-url-searchparams-stringifier.js
@@ -1,6 +1,6 @@
 'use strict';
 
-const common = require('../common');
+require('../common');
 const URLSearchParams = require('url').URLSearchParams;
 const { test, assert_equals } = require('../common/wpt');
 
@@ -121,15 +121,3 @@ test(function() {
     assert_equals(params.toString(), 'a=&a=b');
 }, 'URLSearchParams.toString');
 /* eslint-enable */
-
-// Tests below are not from WPT.
-{
-  const params = new URLSearchParams();
-  common.expectsError(() => {
-    params.toString.call(undefined);
-  }, {
-    code: 'ERR_INVALID_THIS',
-    type: TypeError,
-    message: 'Value of "this" must be of type URLSearchParams'
-  });
-}
diff --git a/test/parallel/test-whatwg-url-setters.js b/test/parallel/test-whatwg-url-setters.js
index 7655e4a2578bb1..a04b6c93eccf3d 100644
--- a/test/parallel/test-whatwg-url-setters.js
+++ b/test/parallel/test-whatwg-url-setters.js
@@ -6,14 +6,10 @@ if (!common.hasIntl) {
   common.skip('missing Intl');
 }
 
-const assert = require('assert');
 const URL = require('url').URL;
 const { test, assert_equals } = require('../common/wpt');
 const fixtures = require('../common/fixtures');
 
-const additionalTestCases =
-  require(fixtures.path('url-setter-tests-additional.js'));
-
 const request = {
   response: require(fixtures.path('url-setter-tests'))
 };
@@ -80,48 +76,3 @@ function runURLSettersTests(all_test_cases) {
 
 startURLSettersTests()
 /* eslint-enable */
-
-// Tests below are not from WPT.
-
-{
-  for (const attributeToBeSet in additionalTestCases) {
-    if (attributeToBeSet === 'comment') {
-      continue;
-    }
-    const testCases = additionalTestCases[attributeToBeSet];
-    for (const testCase of testCases) {
-      let name = `Setting <${testCase.href}>.${attributeToBeSet}` +
-                 ` = "${testCase.new_value}"`;
-      if ('comment' in testCase) {
-        name += ` ${testCase.comment}`;
-      }
-      test(function() {
-        const url = new URL(testCase.href);
-        url[attributeToBeSet] = testCase.new_value;
-        for (const attribute in testCase.expected) {
-          assert_equals(url[attribute], testCase.expected[attribute]);
-        }
-      }, `URL: ${name}`);
-    }
-  }
-}
-
-{
-  const url = new URL('http://example.com/');
-  const obj = {
-    toString() { throw new Error('toString'); },
-    valueOf() { throw new Error('valueOf'); }
-  };
-  const sym = Symbol();
-  const props = Object.getOwnPropertyDescriptors(Object.getPrototypeOf(url));
-  for (const [name, { set }] of Object.entries(props)) {
-    if (set) {
-      assert.throws(() => url[name] = obj,
-                    /^Error: toString$/,
-                    `url.${name} = { toString() { throw ... } }`);
-      assert.throws(() => url[name] = sym,
-                    /^TypeError: Cannot convert a Symbol value to a string$/,
-                    `url.${name} = ${String(sym)}`);
-    }
-  }
-}