Adhere closer to chai-http's true implementation that extends the superagent Request instead of adding custom types. Necessary for being able to use the ca, key, cert and pfx methods with typings intact.

types/chai-http/chai-http-tests.ts

@@ -37,6 +37,25 @@ chai.request(app)
 	.get('/protected')
 	.auth('user', 'pass');
 
+// HTTPS request, from: https://github.com/visionmedia/superagent/commit/6158efbf42cb93d77c1a70887284be783dd7dabe
+const ca = fs.readFileSync('ca.cert.pem');
+const key = fs.readFileSync('key.pem');
+const cert = fs.readFileSync('cert.pem');
+const callback = (err: any, res: ChaiHttp.Response) => {};
+
+chai.request(app)
+    .post('/secure')
+    .ca(ca)
+    .key(key)
+    .cert(cert)
+    .end(callback);
+
+const pfx = fs.readFileSync('cert.pfx');
+chai.request(app)
+    .post('/secure')
+    .pfx(pfx)
+    .end(callback);
+
 chai.request(app)
 	.get('/search')
 	.query({ name: 'foo', limit: 10 });

types/chai-http/index.d.ts

@@ -9,6 +9,8 @@
 /// <reference types="node" />
 /// <reference types="chai" />
 
+import request = require('superagent');
+
 declare global {
 	namespace Chai {
 		interface ChaiStatic {
@@ -53,31 +55,14 @@ declare global {
 			on(event: string, fn: (...args: any[]) => void): void;
 		}
 
-		interface Request extends FinishedRequest {
-			attach(field: string, file: string|Buffer, filename: string): Request;
-			set(field: string, val: string): Request;
-			query(params: any): Request;
-			send(data: any): Request;
-			auth(user: string, name: string): Request;
-			field(name: string, val: string): Request;
-			buffer(): Request;
-			parse(fn: (res: Response, cb: (e?: Error, r?: any) => void) => void): Request;
-			end(callback?: (err: any, res: Response) => void): FinishedRequest;
-		}
-
-		interface FinishedRequest<T = Response> {
-			then<TR1 = T, TR2 = void>(success?: (res: T) => TR1 | PromiseLike<TR1>, failure?: (err: any) => TR2 | PromiseLike<TR2>): FinishedRequest<TR1>;
-			catch(failure?: (err: any) => void): FinishedRequest<T>;
-		}
-
-		interface Agent {
-			get(url: string, callback?: (err: any, res: Response) => void): Request;
-			post(url: string, callback?: (err: any, res: Response) => void): Request;
-			put(url: string, callback?: (err: any, res: Response) => void): Request;
-			head(url: string, callback?: (err: any, res: Response) => void): Request;
-			del(url: string, callback?: (err: any, res: Response) => void): Request;
-			options(url: string, callback?: (err: any, res: Response) => void): Request;
-			patch(url: string, callback?: (err: any, res: Response) => void): Request;
+		interface Agent  {
+			get(url: string, callback?: (err: any, res: Response) => void): request.Request;
+			post(url: string, callback?: (err: any, res: Response) => void): request.Request;
+			put(url: string, callback?: (err: any, res: Response) => void): request.Request;
+			head(url: string, callback?: (err: any, res: Response) => void): request.Request;
+			del(url: string, callback?: (err: any, res: Response) => void): request.Request;
+			options(url: string, callback?: (err: any, res: Response) => void): request.Request;
+			patch(url: string, callback?: (err: any, res: Response) => void): request.Request;
 		}
 
 		interface TypeComparison {