diff --git a/package.json b/package.json
index 1fb53ca5..2dd4780d 100644
--- a/package.json
+++ b/package.json
@@ -7,7 +7,7 @@
   "scripts": {
     "start": "node index.js",
     "karma": "karma start karma.conf.js",
-    "test": "nyc mocha",
+    "test": "nyc mocha && npm run test-ts",
     "snyk": "snyk test",
     "lint": "eslint .",
     "fix": "eslint . --fix",
@@ -17,7 +17,8 @@
     "show-coverage": "npm test; open -a 'Google Chrome' coverage/index.html",
     "clean-install": "rm -rf node_modules && npm install",
     "snyk-protect": "snyk protect",
-    "prepublish": "npm run snyk-protect"
+    "prepublish": "npm run snyk-protect",
+    "test-ts": "mocha -r ts-node/register test/**/*.test.ts"
   },
   "keywords": [
     "intuit-oauth",
@@ -77,6 +78,8 @@
     "winston": "^3.1.0"
   },
   "devDependencies": {
+    "@types/chai": "^4.2.14",
+    "@types/mocha": "^8.0.3",
     "btoa": "^1.2.1",
     "chai": "^4.1.2",
     "chai-as-promised": "^7.1.1",
@@ -89,7 +92,9 @@
     "nyc": "^15.0.1",
     "prettier": "^2.0.5",
     "sinon": "^9.0.2",
-    "snyk": "^1.316.1"
+    "snyk": "^1.316.1",
+    "ts-node": "^9.0.0",
+    "typescript": "^4.0.3"
   },
   "snyk": true
 }
diff --git a/test/types.test.ts b/test/types.test.ts
new file mode 100644
index 00000000..0710e5d3
--- /dev/null
+++ b/test/types.test.ts
@@ -0,0 +1,92 @@
+'use strict';
+import { expect } from 'chai';
+import * as OAuthClient from '../src/OAuthClient';
+
+const AuthResponse = require('../src/response/AuthResponse');
+
+describe('OAuthClient type validation tests', () => {
+    let oAuthClientConfig;
+
+    beforeEach(() => {
+        oAuthClientConfig = {
+            clientId: 'clientId',
+            clientSecret: 'clientSecret',
+            environment: 'sandbox',
+            redirectUri: 'http://localhost:8000/callback'
+    };
+    });
+
+    it('environment should have appropriate fields and types', () => {
+        const result = OAuthClient.environment;
+        expect(typeof result).to.equal('object');
+        expect(result.sandbox).to.equal('https://sandbox-quickbooks.api.intuit.com/');
+        expect(result.xyz).to.be.undefined;
+    });
+
+    it('scopes should have appropriate fields and types', () => {
+        const result = OAuthClient.scopes;
+        expect(typeof result).to.equal('object');
+        expect(result.Accounting).to.equal('com.intuit.quickbooks.accounting');
+        expect(typeof result.Accounting).to.equal('string');
+        expect(result.accounting).to.be.undefined;
+    });
+
+    it('OAuthClientConfig should have appropriate fields and types', () => {
+        expect(typeof oAuthClientConfig.clientId).to.equal('string');
+        expect(typeof oAuthClientConfig.clientSecret).to.equal('string');
+        expect(typeof oAuthClientConfig.environment).to.equal('string');
+        expect(typeof oAuthClientConfig.redirectUri).to.equal('string');
+    });
+
+    it('Should create OAuthClient with appropriate fields and types for valid OAuthClientConfig', () => {
+        const oAuthClient = new OAuthClient({
+            oAuthClientConfig
+        });
+        expect(typeof oAuthClient).to.equal('object');
+        expect(typeof oAuthClient.token).to.equal('object');
+        expect(typeof oAuthClient.logging).to.equal('boolean');
+        expect(typeof oAuthClient.logger).to.equal('object');
+        expect(typeof oAuthClient.state).to.equal('object');
+    });
+
+    it('should create new access token instance with appropriate fields and types for valid OAuthClient', () => {
+        const oAuthClient = new OAuthClient({
+            oAuthClientConfig
+        });
+        const accessToken = oAuthClient.getToken();
+        expect(typeof accessToken).to.equal('object');
+        expect(typeof accessToken.realmId).to.equal('string');
+        expect(typeof accessToken.token_type).to.equal('string');
+        expect(typeof accessToken.refresh_token).to.equal('string');
+        expect(typeof accessToken.expires_in).to.equal('number');
+        expect(typeof accessToken.x_refresh_token_expires_in).to.equal('number');
+        expect(typeof accessToken.id_token).to.equal('string');
+        expect(typeof accessToken.latency).to.equal('number');
+        expect(typeof accessToken.createdAt).to.equal('number');
+    });
+
+    it('should create new auth response instance with appropriate fields and types for valid accessToken', () => {
+        const oAuthClient = new OAuthClient({
+            oAuthClientConfig
+        });
+        const accessToken = oAuthClient.getToken();
+        const authResponse = new AuthResponse({ token: accessToken });
+        expect(typeof authResponse.token).to.equal('object');
+        expect(typeof authResponse.response).to.equal('string');
+        expect(typeof authResponse.body).to.equal('string');
+        expect(typeof authResponse.json).to.equal('object');
+        expect(typeof authResponse.intuit_tid).to.equal('string');
+    });
+
+    it('Should create OAuthClientError with appropriate fields and types for empty authResponse', () => {
+        const oAuthClient = new OAuthClient({
+            oAuthClientConfig
+        });
+        const oAuthClientError = oAuthClient.createError(new Error(), null);
+        expect(typeof oAuthClientError.error).to.equal('string');
+        expect(typeof oAuthClientError.authResponse).to.equal('string');
+        expect(typeof oAuthClientError.intuit_tid).to.equal('string');
+        expect(typeof oAuthClientError.originalMessage).to.equal('string');
+        expect(typeof oAuthClientError.error_description).to.equal('string');
+    });
+});