Add TypeScript definitions

package.json

@@ -3,6 +3,7 @@
   "version": "3.0.1",
   "description": "Creates a minimal Express server for testing",
   "main": "src/index.js",
+  "types": "src/index.d.ts",
   "scripts": {
     "test": "xo && nyc ava",
     "coverage": "nyc report --reporter=text-lcov | coveralls"

src/index.d.ts

@@ -0,0 +1,27 @@
+import {Express} from 'express';
+import {Server as HttpServer} from 'http';
+import {Server as HttpsServer} from 'https';
+
+declare namespace createTestServer {
+	interface Options {
+		bodyParser?: false | object;
+		certificate?: string | {days?: number, commonName?: string};
+	}
+
+	interface Server extends Omit<Express, 'listen' | 'close'> {
+		url: string | undefined;
+		port: number | undefined;
+		sslUrl: string | undefined;
+		sslPort: number | undefined;
+		caCert: string;
+		http: HttpServer;
+		https: HttpsServer;
+
+		listen: () => Promise<void>;
+		close: () => Promise<void>;
+	}
+}
+
+declare function createTestServer(options: createTestServer.Options): Promise<createTestServer.Server>;
+
+export = createTestServer;