Augment supertest .expect(status) to log the response body when failing

test/test-lib/init-tests.ts

@@ -1,13 +1,18 @@
 import jsonwebtoken from 'jsonwebtoken';
 import * as fixtures from './fixtures';
-import { supertest, UserObjectParam } from './supertest';
+import {
+	supertest,
+	augmentStatusAssertionError,
+	UserObjectParam,
+} from './supertest';
 import { version } from './versions';
 import {
 	getContractRepos,
 	synchronizeContracts,
 } from '../../src/features/contracts';
 
 export const preInit = async () => {
+	augmentStatusAssertionError();
 	await import('./aws-mock');
 	await import('./contracts-mock');
 

test/test-lib/supertest.ts

@@ -1,13 +1,49 @@
 import { app } from '../../init';
 import $supertest from 'supertest';
 import { User } from '../../src/infra/auth/jwt-passport';
+import { ThisShouldNeverHappenError } from '../../src/infra/error-handling';
 
 export type UserObjectParam = Partial<User & { token: string }>;
 
+export const augmentStatusAssertionError = () => {
+	const originalExpect: $supertest.Test['expect'] =
+		$supertest.Test.prototype.expect;
+	/**
+	 * This enhances `.expect(statusCode, ...)` to also log the response body when
+	 * the statusCode is different than expected, to make the original error more useful.
+	 */
+	$supertest.Test.prototype.expect = function (this: $supertest.Test, ...args) {
+		const [expectedStatus] = args;
+		let supertestFluentChain = this;
+		if (typeof expectedStatus === 'number') {
+			// TODO: Switch `.bind()` to `.call()` once TS is able to pick the correct overload.
+			supertestFluentChain = originalExpect.bind(supertestFluentChain)(
+				(res) => {
+					const error = this._assertStatus(expectedStatus, res);
+					if (error) {
+						error.message += `, with response body:\n${JSON.stringify(
+							res.body,
+							null,
+							2,
+						)}`;
+						throw error;
+					}
+				},
+			);
+		}
+		return originalExpect.apply(supertestFluentChain, args);
+	} satisfies typeof originalExpect;
+};
+
 export const supertest = function (user?: string | UserObjectParam) {
 	// Can be an object with `token`, a JWT string or an API key string
 	let token = user;
-	if (typeof user === 'object' && user.token) {
+	if (user != null && typeof user === 'object') {
+		if (user.token == null) {
+			throw ThisShouldNeverHappenError(
+				'Heads-up: You provided an object as a parameter to supertest that does not include a token, making requests that require authentication to always return 401!!!',
+			);
+		}
 		token = user.token;
 	}
 	// We have to cast `as any` because the types are poorly maintained

typings/supertest-extension.d.ts

@@ -0,0 +1,10 @@
+import 'supertest';
+
+// Augment supertest
+declare module 'supertest' {
+	interface Test {
+		_assertStatus(status: number, res: Response): Error | undefined;
+	}
+
+	function Test(app: any, method: string, path: string): Test;
+}