diff --git a/packages/firestore/test/unit/core/webchannel_wrapper.test.ts b/packages/firestore/test/unit/core/webchannel_wrapper.test.ts
new file mode 100644
index 00000000000..e999eeeeb98
--- /dev/null
+++ b/packages/firestore/test/unit/core/webchannel_wrapper.test.ts
@@ -0,0 +1,268 @@
+/**
+ * @license
+ * Copyright 2022 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Add some unit tests for classes exported from @firebase/webchannel-wrapper.
+// These tests are mostly to ensure that the exported classes correctly map to
+// underlying functionality from google-closure-library.
+
+import { Integer } from '@firebase/webchannel-wrapper';
+import { expect } from 'chai';
+
+describe('Integer', () => {
+  it('constructor should create distinct instances', () => {
+    const instance1 = new Integer([1], 0);
+    const instance2 = new Integer([1], 0);
+    expect(instance1).is.instanceof(Integer);
+    expect(instance2).is.instanceof(Integer);
+    expect(instance1).is.not.equal(instance2);
+  });
+
+  it('constructor should construct 1 and -1, 2 and -2', () => {
+    const positiveOne = new Integer([1], 0);
+    expect(positiveOne.toNumber()).equals(1);
+    const negativeOne = new Integer([-1], -1);
+    expect(negativeOne.toNumber()).equals(-1);
+    const positiveTwo = new Integer([2], 0);
+    expect(positiveTwo.toNumber()).equals(2);
+    const negativeTwo = new Integer([-2], -1);
+    expect(negativeTwo.toNumber()).equals(-2);
+  });
+
+  it('constructor should construct big positive values', () => {
+    expect(new Integer([0xff], 0).toNumber()).equals(255);
+    expect(new Integer([0xffff], 0).toNumber()).equals(65535);
+    expect(new Integer([0xffffff], 0).toNumber()).equals(16777215);
+    expect(new Integer([0xffffffff], 0).toNumber()).equals(4294967295);
+    expect(new Integer([0, 1], 0).toNumber()).equals(4294967296);
+    expect(new Integer([1, 1], 0).toNumber()).equals(4294967297);
+    expect(new Integer([0xfffffffe, 1], 0).toNumber()).equals(8589934590);
+    expect(new Integer([0xffffffff, 1], 0).toNumber()).equals(8589934591);
+    expect(new Integer([0, 2], 0).toNumber()).equals(8589934592);
+    expect(new Integer([1, 2], 0).toNumber()).equals(8589934593);
+    expect(
+      new Integer(
+        [0x992ce530, 0xbc1f3bbb, 0x2080e2ee, 0xe53c0595],
+        0
+      ).toString()
+    ).equals('304704862073361391914321619654827369776');
+  });
+
+  it('constructor should construct big negative values', () => {
+    expect(new Integer([0xffffffff], -1).toNumber()).equals(-1);
+    expect(new Integer([0xfffffffe], -1).toNumber()).equals(-2);
+    expect(new Integer([0xfffffffd], -1).toNumber()).equals(-3);
+    expect(new Integer([0xfffffff0], -1).toNumber()).equals(-16);
+    expect(new Integer([0xffffff00], -1).toNumber()).equals(-256);
+    expect(new Integer([0xfffff000], -1).toNumber()).equals(-4096);
+    expect(new Integer([0xffff0000], -1).toNumber()).equals(-65536);
+    expect(new Integer([0xfff00000], -1).toNumber()).equals(-1048576);
+    expect(new Integer([0xff000000], -1).toNumber()).equals(-16777216);
+    expect(new Integer([0xf0000000], -1).toNumber()).equals(-268435456);
+    expect(new Integer([0x00000001], -1).toNumber()).equals(-4294967295);
+    expect(new Integer([0x00000000], -1).toNumber()).equals(-4294967296);
+    expect(new Integer([0x00000000, 0xffffffff], -1).toNumber()).equals(
+      -4294967296
+    );
+    expect(new Integer([0xffffffff, 0xfffffffe], -1).toNumber()).equals(
+      -4294967297
+    );
+    expect(new Integer([0xfffffffe, 0xfffffffe], -1).toNumber()).equals(
+      -4294967298
+    );
+  });
+
+  it('add() should produce the sum of the two numbers', () => {
+    expect(Integer.fromNumber(0).add(Integer.fromNumber(0)).toNumber()).equals(
+      0
+    );
+    expect(Integer.fromNumber(1).add(Integer.fromNumber(1)).toNumber()).equals(
+      2
+    );
+    expect(
+      Integer.fromNumber(0xffffffff).add(Integer.fromNumber(1)).toNumber()
+    ).equals(4294967296);
+    expect(
+      Integer.fromString('304704862073361391914321619654827369776')
+        .add(Integer.fromString('77393247566944052149773810817307943505'))
+        .toString()
+    ).equals('382098109640305444064095430472135313281');
+    expect(Integer.fromNumber(0).add(Integer.fromNumber(-1)).toNumber()).equals(
+      -1
+    );
+  });
+
+  it('multiply() should produce the product of the two numbers', () => {
+    expect(
+      Integer.fromNumber(0).multiply(Integer.fromNumber(0)).toNumber()
+    ).equals(0);
+    expect(
+      Integer.fromNumber(1).multiply(Integer.fromNumber(0)).toNumber()
+    ).equals(0);
+    expect(
+      Integer.fromNumber(1).multiply(Integer.fromNumber(1)).toNumber()
+    ).equals(1);
+    expect(
+      Integer.fromNumber(9).multiply(Integer.fromNumber(3)).toNumber()
+    ).equals(27);
+    expect(
+      Integer.fromNumber(0xffffffff)
+        .multiply(Integer.fromNumber(0xca11ba11))
+        .toString()
+    ).equals('14560623649052575215');
+    expect(
+      Integer.fromString('304704862073361391914321619654827369776')
+        .multiply(Integer.fromString('77393247566944052149773810817307943505'))
+        .toString()
+    ).equals(
+      '23582098825295199538298333106941184620809785262540690532878112097410752504880'
+    );
+    expect(
+      Integer.fromNumber(5).multiply(Integer.fromNumber(-1)).toNumber()
+    ).equals(-5);
+  });
+
+  it('modulo() should produce the division remainder of the two numbers', () => {
+    expect(() => Integer.fromNumber(0).modulo(Integer.fromNumber(0))).to.throw(
+      'division by zero'
+    );
+    expect(() => Integer.fromNumber(42).modulo(Integer.fromNumber(0))).to.throw(
+      'division by zero'
+    );
+    expect(
+      Integer.fromNumber(20).modulo(Integer.fromNumber(1)).toNumber()
+    ).equals(0);
+    expect(
+      Integer.fromNumber(2).modulo(Integer.fromNumber(2)).toNumber()
+    ).equals(0);
+    expect(
+      Integer.fromNumber(3).modulo(Integer.fromNumber(2)).toNumber()
+    ).equals(1);
+    expect(
+      Integer.fromNumber(4).modulo(Integer.fromNumber(2)).toNumber()
+    ).equals(0);
+    expect(
+      Integer.fromNumber(0xffffffff)
+        .modulo(Integer.fromNumber(0xca11ba11))
+        .toNumber()
+    ).equals(904807918);
+    expect(
+      Integer.fromString('304704862073361391914321619654827369776')
+        .modulo(Integer.fromString('77393247566944052149773810817307943505'))
+        .toString()
+    ).equals('72525119372529235465000187202903539261');
+    expect(
+      Integer.fromString('304704862073361391914321619654827369776')
+        .modulo(Integer.fromNumber(313))
+        .toNumber()
+    ).equals(167);
+  });
+
+  it('compare() should correctly compare two numbers for order', () => {
+    const numbers = Object.freeze([
+      Integer.fromNumber(-4294967298),
+      Integer.fromNumber(-2),
+      Integer.fromNumber(-1),
+      Integer.fromNumber(0),
+      Integer.fromNumber(1),
+      Integer.fromNumber(2),
+      Integer.fromNumber(0xffffffff),
+      Integer.fromString('77393247566944052149773810817307943505'),
+      Integer.fromString('304704862073361391914321619654827369776')
+    ]);
+    for (let i1 = 0; i1 < numbers.length; i1++) {
+      for (let i2 = 0; i2 < numbers.length; i2++) {
+        const num1 = numbers[i1];
+        const num2 = numbers[i2];
+        const expected = i1 === i2 ? 0 : i1 < i2 ? -1 : 1;
+        expect(num1.compare(num2)).equals(expected);
+      }
+    }
+  });
+
+  it('toNumber() should return the correct number', () => {
+    const one = Integer.fromNumber(1);
+    const two = Integer.fromNumber(2);
+    expect(Integer.fromNumber(0).toNumber()).equals(0);
+    expect(Integer.fromNumber(1).toNumber()).equals(1);
+    expect(Integer.fromNumber(-1).toNumber()).equals(-1);
+    expect(Integer.fromNumber(Number.MAX_SAFE_INTEGER).toNumber()).equals(
+      Number.MAX_SAFE_INTEGER
+    );
+    expect(Integer.fromNumber(Number.MIN_SAFE_INTEGER).toNumber()).equals(
+      Number.MIN_SAFE_INTEGER
+    );
+    expect(
+      Integer.fromNumber(Number.MAX_SAFE_INTEGER).add(one).toNumber()
+    ).equals(Number.MAX_SAFE_INTEGER + 1);
+    expect(
+      Integer.fromNumber(Number.MAX_SAFE_INTEGER).add(two).toNumber()
+    ).equals(Number.MAX_SAFE_INTEGER + 1);
+  });
+
+  it('toString() should return the correct number', () => {
+    const one = Integer.fromNumber(1);
+    const two = Integer.fromNumber(2);
+    expect(Integer.fromNumber(0).toString()).equals('0');
+    expect(Integer.fromNumber(1).toString()).equals('1');
+    expect(Integer.fromNumber(-1).toString()).equals('-1');
+    expect(Integer.fromNumber(Number.MAX_SAFE_INTEGER).toString()).equals(
+      '9007199254740991'
+    );
+    expect(Integer.fromNumber(Number.MIN_SAFE_INTEGER).toString()).equals(
+      '-9007199254740991'
+    );
+    expect(
+      Integer.fromNumber(Number.MAX_SAFE_INTEGER).add(one).toString()
+    ).equals('9007199254740992');
+    expect(
+      Integer.fromNumber(Number.MAX_SAFE_INTEGER).add(two).toString()
+    ).equals('9007199254740993');
+    expect(
+      Integer.fromString('304704862073361391914321619654827369776').toString()
+    ).equals('304704862073361391914321619654827369776');
+
+    expect(Integer.fromNumber(0).toString(2)).equals('0');
+    expect(Integer.fromNumber(43981).toString(2)).equals('1010101111001101');
+    expect(Integer.fromNumber(43981).toString(8)).equals('125715');
+    expect(Integer.fromNumber(43981).toString(10)).equals('43981');
+    expect(Integer.fromNumber(43981).toString(16)).equals('abcd');
+  });
+
+  it('fromNumber() create a new Integer with the given value', () => {
+    // The tests for toString() and toNumber() cover this method.
+  });
+
+  it('fromString() create a new Integer with the given value', () => {
+    expect(Integer.fromString('0').toNumber()).equals(0);
+    expect(Integer.fromString('1').toNumber()).equals(1);
+    expect(Integer.fromString('-1').toNumber()).equals(-1);
+    expect(Integer.fromString('42').toNumber()).equals(42);
+    expect(Integer.fromString('9007199254740991').toNumber()).equals(
+      Number.MAX_SAFE_INTEGER
+    );
+    expect(Integer.fromString('-9007199254740991').toNumber()).equals(
+      Number.MIN_SAFE_INTEGER
+    );
+    expect(
+      Integer.fromString('304704862073361391914321619654827369776').toString()
+    ).equals('304704862073361391914321619654827369776');
+
+    expect(Integer.fromString('abcd', 16).toNumber()).equals(43981);
+    expect(Integer.fromString('125715', 8).toNumber()).equals(43981);
+    expect(Integer.fromString('1010101111001101', 2).toNumber()).equals(43981);
+  });
+});
diff --git a/packages/webchannel-wrapper/src/index.d.ts b/packages/webchannel-wrapper/src/index.d.ts
index 4a1f45f1d70..faa6c7e7ed6 100644
--- a/packages/webchannel-wrapper/src/index.d.ts
+++ b/packages/webchannel-wrapper/src/index.d.ts
@@ -136,3 +136,18 @@ export function getStatEventTarget(): EventTarget;
 export class FetchXmlHttpFactory {
   constructor(options: {});
 }
+
+// See https://google.github.io/closure-library/api/goog.math.Integer.html
+// Unit test are written in
+// packages/firestore/test/unit/core/webchannel_wrapper.test.ts
+export class Integer {
+  constructor(bits: Array<number>, sign: number);
+  add(other: Integer): Integer;
+  multiply(other: Integer): Integer;
+  modulo(other: Integer): Integer;
+  compare(other: Integer): number;
+  toNumber(): number;
+  toString(opt_radix?: number): string;
+  static fromNumber(value: number): Integer;
+  static fromString(str: string, opt_radix?: number): Integer;
+}
diff --git a/packages/webchannel-wrapper/src/index.js b/packages/webchannel-wrapper/src/index.js
index c51f7d68ba3..4786a2f8321 100644
--- a/packages/webchannel-wrapper/src/index.js
+++ b/packages/webchannel-wrapper/src/index.js
@@ -78,6 +78,16 @@ goog.net.XhrIo.prototype['send'] = goog.net.XhrIo.prototype.send;
 goog.net.XhrIo.prototype['setWithCredentials'] =
   goog.net.XhrIo.prototype.setWithCredentials;
 
+goog.require('goog.math.Integer');
+goog.math.Integer.prototype['add'] = goog.math.Integer.prototype.add;
+goog.math.Integer.prototype['multiply'] = goog.math.Integer.prototype.multiply;
+goog.math.Integer.prototype['modulo'] = goog.math.Integer.prototype.modulo;
+goog.math.Integer.prototype['compare'] = goog.math.Integer.prototype.compare;
+goog.math.Integer.prototype['toNumber'] = goog.math.Integer.prototype.toNumber;
+goog.math.Integer.prototype['toString'] = goog.math.Integer.prototype.toString;
+goog.math.Integer['fromNumber'] = goog.math.Integer.fromNumber;
+goog.math.Integer['fromString'] = goog.math.Integer.fromString;
+
 module['exports']['createWebChannelTransport'] =
   goog.net.createWebChannelTransport;
 module['exports']['getStatEventTarget'] =
@@ -89,3 +99,4 @@ module['exports']['Stat'] = goog.labs.net.webChannel.requestStats.Stat;
 module['exports']['FetchXmlHttpFactory'] = goog.net.FetchXmlHttpFactory;
 module['exports']['WebChannel'] = goog.net.WebChannel;
 module['exports']['XhrIo'] = goog.net.XhrIo;
+module['exports']['Integer'] = goog.math.Integer;