diff --git a/src/mock-doc/document.ts b/src/mock-doc/document.ts
index e97c1bd3b3c..f77196c6040 100644
--- a/src/mock-doc/document.ts
+++ b/src/mock-doc/document.ts
@@ -5,20 +5,18 @@ import { MockDocumentFragment } from './document-fragment';
 import { MockDocumentTypeNode } from './document-type-node';
 import { createElement, createElementNS, MockBaseElement } from './element';
 import { resetEventListeners } from './event';
-import { MockElement, MockHTMLElement, MockTextNode, resetElement } from './node';
+import { MockElement, MockHTMLElement, MockNode, MockTextNode, resetElement } from './node';
 import { parseHtmlToFragment } from './parse-html';
 import { parseDocumentUtil } from './parse-util';
 import { MockWindow } from './window';
 
-export class MockDocument extends MockHTMLElement {
+export class MockDocument extends MockNode {
   defaultView: any;
   cookie: string;
   referrer: string;
 
   constructor(html: string | boolean = null, win: any = null) {
-    super(null, null);
-    this.nodeName = NODE_NAMES.DOCUMENT_NODE;
-    this.nodeType = NODE_TYPES.DOCUMENT_NODE;
+    super(null, NODE_TYPES.DOCUMENT_NODE, NODE_NAMES.DOCUMENT_NODE, null);
     this.defaultView = win;
     this.cookie = '';
     this.referrer = '';
@@ -42,17 +40,13 @@ export class MockDocument extends MockHTMLElement {
     }
   }
 
-  override get dir() {
+  get dir() {
     return this.documentElement.dir;
   }
-  override set dir(value: string) {
+  set dir(value: string) {
     this.documentElement.dir = value;
   }
 
-  override get localName(): undefined {
-    return undefined;
-  }
-
   get location() {
     if (this.defaultView != null) {
       return (this.defaultView as Window).location;
@@ -225,14 +219,14 @@ export class MockDocument extends MockHTMLElement {
     return getElementsByName(this, elmName.toLowerCase());
   }
 
-  override get title() {
+  get title() {
     const title = this.head.childNodes.find((elm) => elm.nodeName === 'TITLE') as MockElement;
     if (title != null && typeof title.textContent === 'string') {
       return title.textContent.trim();
     }
     return '';
   }
-  override set title(value: string) {
+  set title(value: string) {
     const head = this.head;
     let title = head.childNodes.find((elm) => elm.nodeName === 'TITLE') as MockElement;
     if (title == null) {
@@ -297,7 +291,7 @@ const DOC_KEY_KEEPERS = new Set([
   '_shadowRoot',
 ]);
 
-export function getElementById(elm: MockElement, id: string): MockElement {
+export function getElementById(elm: MockElement | MockDocument, id: string): MockElement {
   const children = elm.children;
   for (let i = 0, ii = children.length; i < ii; i++) {
     const childElm = children[i];
@@ -312,7 +306,7 @@ export function getElementById(elm: MockElement, id: string): MockElement {
   return null;
 }
 
-function getElementsByName(elm: MockElement, elmName: string, foundElms: MockElement[] = []) {
+function getElementsByName(elm: MockElement | MockDocument, elmName: string, foundElms: MockElement[] = []) {
   const children = elm.children;
   for (let i = 0, ii = children.length; i < ii; i++) {
     const childElm = children[i];
diff --git a/src/mock-doc/event.ts b/src/mock-doc/event.ts
index 156e47eb939..eefc2b7e675 100644
--- a/src/mock-doc/event.ts
+++ b/src/mock-doc/event.ts
@@ -43,10 +43,10 @@ export class MockEvent {
    * @ref https://developer.mozilla.org/en-US/docs/Web/API/Event/composedPath
    * @returns a composed path of the event
    */
-  composedPath(): MockElement[] {
-    const composedPath: MockElement[] = [];
+  composedPath(): (MockElement | MockDocument)[] {
+    const composedPath: (MockElement | MockDocument)[] = [];
 
-    let currentElement = this.target;
+    let currentElement: MockElement | MockDocument = this.target;
 
     while (currentElement) {
       composedPath.push(currentElement);
@@ -63,7 +63,7 @@ export class MockEvent {
        * with the document object instead of the parent element since the parent element
        * is `null` for HTML elements.
        */
-      if (currentElement.parentElement == null && currentElement.tagName === 'HTML') {
+      if (currentElement.parentElement == null && 'tagName' in currentElement && currentElement.tagName === 'HTML') {
         currentElement = currentElement.ownerDocument;
       } else {
         currentElement = currentElement.parentElement;
diff --git a/src/mock-doc/node.ts b/src/mock-doc/node.ts
index 6c775831f86..02082003f93 100644
--- a/src/mock-doc/node.ts
+++ b/src/mock-doc/node.ts
@@ -33,6 +33,36 @@ export class MockNode {
     this.childNodes = [];
   }
 
+  get children(): MockElement[] {
+    return this.childNodes.filter((n) => n.nodeType === NODE_TYPES.ELEMENT_NODE) as MockElement[];
+  }
+
+  get childElementCount() {
+    return this.childNodes.filter((n) => n.nodeType === NODE_TYPES.ELEMENT_NODE).length;
+  }
+
+  get firstElementChild(): MockElement | null {
+    return this.children[0] || null;
+  }
+
+  addEventListener(type: string, handler: (ev?: any) => void) {
+    addEventListener(this, type, handler);
+  }
+
+  removeEventListener(type: string, handler: any) {
+    removeEventListener(this, type, handler);
+  }
+
+  dispatchEvent(ev: MockEvent) {
+    return dispatchEvent(this, ev);
+  }
+
+  getElementsByTagName(tagName: string) {
+    const results: MockElement[] = [];
+    getElementsByTagName(this, tagName.toLowerCase(), results);
+    return results;
+  }
+
   appendChild(newNode: MockNode) {
     if (newNode.nodeType === NODE_TYPES.DOCUMENT_FRAGMENT_NODE) {
       const nodes = newNode.childNodes.slice();
@@ -195,6 +225,14 @@ export class MockNode {
     return null;
   }
 
+  querySelector(selector: string) {
+    return selectOne(selector, this);
+  }
+
+  querySelectorAll(selector: string) {
+    return selectAll(selector, this);
+  }
+
   get textContent() {
     return this._nodeValue ?? '';
   }
@@ -249,10 +287,6 @@ Testing components with ElementInternals is fully supported in e2e tests.`,
     this.__attributeMap = null;
   }
 
-  addEventListener(type: string, handler: (ev?: any) => void) {
-    addEventListener(this, type, handler);
-  }
-
   attachShadow(_opts: ShadowRootInit) {
     const shadowRoot = this.ownerDocument.createDocumentFragment();
     this.shadowRoot = shadowRoot;
@@ -309,14 +343,6 @@ Testing components with ElementInternals is fully supported in e2e tests.`,
     this.__attributeMap = attrs;
   }
 
-  get children() {
-    return this.childNodes.filter((n) => n.nodeType === NODE_TYPES.ELEMENT_NODE) as MockElement[];
-  }
-
-  get childElementCount() {
-    return this.childNodes.filter((n) => n.nodeType === NODE_TYPES.ELEMENT_NODE).length;
-  }
-
   get className() {
     return this.getAttributeNS(null, 'class') || '';
   }
@@ -341,7 +367,7 @@ Testing components with ElementInternals is fully supported in e2e tests.`,
   closest(selector: string) {
     let elm = this;
     while (elm != null) {
-      if (elm.matches(selector)) {
+      if ('matches' in elm && elm.matches(selector)) {
         return elm;
       }
       elm = elm.parentNode as any;
@@ -360,14 +386,6 @@ Testing components with ElementInternals is fully supported in e2e tests.`,
     this.setAttributeNS(null, 'dir', value);
   }
 
-  dispatchEvent(ev: MockEvent) {
-    return dispatchEvent(this, ev);
-  }
-
-  get firstElementChild(): MockElement | null {
-    return this.children[0] || null;
-  }
-
   focus(_options?: { preventScroll?: boolean }) {
     dispatchEvent(
       this,
@@ -613,20 +631,6 @@ Testing components with ElementInternals is fully supported in e2e tests.`,
     return results;
   }
 
-  getElementsByTagName(tagName: string) {
-    const results: MockElement[] = [];
-    getElementsByTagName(this, tagName.toLowerCase(), results);
-    return results;
-  }
-
-  querySelector(selector: string) {
-    return selectOne(selector, this);
-  }
-
-  querySelectorAll(selector: string) {
-    return selectAll(selector, this);
-  }
-
   removeAttribute(attrName: string) {
     if (attrName === 'style') {
       delete this.__style;
@@ -651,10 +655,6 @@ Testing components with ElementInternals is fully supported in e2e tests.`,
     }
   }
 
-  removeEventListener(type: string, handler: any) {
-    removeEventListener(this, type, handler);
-  }
-
   setAttribute(attrName: string, value: any) {
     if (attrName === 'style') {
       this.style = value;
@@ -1059,7 +1059,7 @@ function getElementsByClassName(elm: MockElement, classNames: string[], foundElm
   }
 }
 
-function getElementsByTagName(elm: MockElement, tagName: string, foundElms: MockElement[]) {
+function getElementsByTagName(elm: MockNode, tagName: string, foundElms: MockElement[]) {
   const children = elm.children;
   for (let i = 0, ii = children.length; i < ii; i++) {
     const childElm = children[i];
diff --git a/src/mock-doc/selector.ts b/src/mock-doc/selector.ts
index 9bde4810bba..8105eb8f3e8 100644
--- a/src/mock-doc/selector.ts
+++ b/src/mock-doc/selector.ts
@@ -1,4 +1,4 @@
-import { MockElement } from './node';
+import { MockNode } from './node';
 import jQuery from './third-party/jquery';
 
 /**
@@ -8,7 +8,7 @@ import jQuery from './third-party/jquery';
  * @param elm an element within which to find matching elements
  * @returns whether the element matches the selector
  */
-export function matches(selector: string, elm: MockElement): boolean {
+export function matches(selector: string, elm: MockNode): boolean {
   try {
     const r = jQuery.find(selector, undefined, undefined, [elm]);
     return r.length > 0;
@@ -25,7 +25,7 @@ export function matches(selector: string, elm: MockElement): boolean {
  * @param elm the element within which to find a matching element
  * @returns the first matching element, or null if none is found
  */
-export function selectOne(selector: string, elm: MockElement) {
+export function selectOne(selector: string, elm: MockNode) {
   try {
     const r = jQuery.find(selector, elm, undefined, undefined);
     return r[0] || null;
@@ -42,7 +42,7 @@ export function selectOne(selector: string, elm: MockElement) {
  * @param elm an element within which to find matching elements
  * @returns all matching elements
  */
-export function selectAll(selector: string, elm: MockElement): any {
+export function selectAll(selector: string, elm: MockNode): any {
   try {
     return jQuery.find(selector, elm, undefined, undefined);
   } catch (e) {
diff --git a/src/mock-doc/test/element.spec.ts b/src/mock-doc/test/element.spec.ts
index 26ff322b745..2c1eade8048 100644
--- a/src/mock-doc/test/element.spec.ts
+++ b/src/mock-doc/test/element.spec.ts
@@ -511,7 +511,6 @@ describe('element', () => {
     expect(doc.createElement('input').localName).toBe('input');
     expect(doc.createElement('a').localName).toBe('a');
     expect(doc.createElement('datalist').localName).toBe('datalist');
-    expect(doc.localName).toBe(undefined);
     expect(doc.createElement('svg').localName).toBe('svg');
     expect((document.childNodes[1] as any).localName).toBe('html');
   });
diff --git a/src/mock-doc/test/selector.spec.ts b/src/mock-doc/test/selector.spec.ts
index 4fde447d0f0..c2454313c2d 100644
--- a/src/mock-doc/test/selector.spec.ts
+++ b/src/mock-doc/test/selector.spec.ts
@@ -238,7 +238,7 @@ describe('selector', () => {
 
     expect(() => doc.querySelector(selector)).toThrow(expectedMessage);
     expect(() => doc.querySelectorAll(selector)).toThrow(expectedMessage);
-    expect(() => doc.matches(selector)).toThrow(expectedMessage);
+    expect(() => doc.body.matches(selector)).toThrow(expectedMessage);
   });
 
   it('should error for combinations of problematic selectors', () => {