add FakeRedis testing utility

packages/backend/test/misc/FakeRedis.ts

@@ -0,0 +1,145 @@
+/*
+ * SPDX-FileCopyrightText: hazelnoot and other Sharkey contributors
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import * as Redis from 'ioredis';
+
+export type RedisKey = Redis.RedisKey;
+export type RedisString = Buffer | string;
+export type RedisNumber = string | number;
+export type RedisValue = RedisKey | RedisString | RedisNumber;
+export type RedisCallback<T = unknown> = Redis.Callback<T>;
+
+export type Ok = 'OK';
+export const ok = 'OK' as const;
+
+export type FakeRedis = Redis.Redis;
+export interface FakeRedisConstructor {
+	new (): FakeRedis;
+}
+
+/**
+ * Fake implementation of Redis that pretends to connect but throws on any operation.
+ */
+export const FakeRedis: FakeRedisConstructor = createFakeRedis();
+
+function createFakeRedis(): FakeRedisConstructor {
+	class FakeRedis implements Partial<Redis.Redis> {
+		async connect(callback?: RedisCallback<void>): Promise<void> {
+			// no-op
+			callback?.(null);
+		}
+
+		async hello(...callbacks: (undefined | string | number | Buffer | RedisCallback<unknown[]>)[]): Promise<unknown[]> {
+			// no-op
+			const callback = callbacks.find(c => typeof(c) === 'function');
+			callback?.(null, []);
+			return [];
+		}
+
+		async auth(...callbacks: (undefined | string | Buffer | RedisCallback<Ok>)[]): Promise<Ok> {
+			const callback = callbacks.find(c => typeof(c) === 'function');
+			callback?.(null, ok);
+			return ok;
+		}
+
+		async quit(callback?: RedisCallback<Ok>) {
+			// no-op
+			callback?.(null, ok);
+			return ok;
+		}
+
+		async save(callback?: RedisCallback<Ok>) {
+			// no-op
+			callback?.(null, ok);
+			return ok;
+		}
+
+		async sync(callback?: RedisCallback<Ok>) {
+			// no-op
+			callback?.(null, ok);
+			return ok;
+		}
+
+		disconnect(): void {
+			// no-op
+		}
+
+		end(): void {
+			// no-op
+		}
+	}
+
+	const fakeProto = FakeRedis.prototype as Partial<Redis.Redis>;
+	const redisProto = Redis.Redis.prototype as Partial<Redis.Redis>;
+
+	// Override all methods and accessors from Redis
+	for (const [key, property] of allProps(redisProto)) {
+		// Skip anything already defined
+		if (Reflect.has(fakeProto, key)) {
+			continue;
+		}
+
+		if (property.get || property.set) {
+			// Stub accessors
+			Reflect.defineProperty(fakeProto, key, {
+				...property,
+				get: property.get ? stub(property.get.name || key) : undefined,
+				set: property.set ? stub(property.set.name || key) : undefined,
+			});
+		} else if (property.value && typeof(property.value) === 'function') {
+			// Stub methods
+			Reflect.defineProperty(fakeProto, key, {
+				...property,
+				value: stub(property.value.name || key),
+			});
+		}
+	}
+
+	// Fixup protoype
+	Reflect.setPrototypeOf(fakeProto, redisProto);
+
+	// test
+	const test = new FakeRedis();
+	if (!(test instanceof Redis.Redis)) {
+		throw new Error('failed to extend');
+	}
+
+	return FakeRedis as FakeRedisConstructor;
+}
+
+function *allProps(obj: object | null): Generator<[PropertyKey, PropertyDescriptor]> {
+	while (obj != null) {
+		for (const key of Reflect.ownKeys(obj)) {
+			const prop = Reflect.getOwnPropertyDescriptor(obj, key);
+			if (prop) {
+				yield [key, prop];
+			}
+		}
+
+		obj = Object.getPrototypeOf(obj);
+	}
+}
+
+function stub(name: PropertyKey) {
+	if (typeof(name) === 'symbol') {
+		name = `[symbol.${name.description || '<anonymous>'}]`;
+	} else if (typeof(name) === 'number') {
+		name = String(name);
+	}
+
+	const stub = () => {
+		throw new Error(`Not Implemented: MockRedis does not support ${name}`);
+	};
+
+	// Make the stub match the original name
+	Object.defineProperty(stub, 'name', {
+		writable: false,
+		enumerable: false,
+		configurable: true,
+		value: name,
+	});
+
+	return stub;
+}