Object.keys(routes).forEach((key) => {
        if (routes[key] instanceof Router) {
            routeMap[key] = routes[key];

        } else if (isString(routes[key])) {
            routeMap[key] = createResourceFactory(resourceKlass, (routes[key] as string), null);

        } else if (isResourceTuple(routes[key])) {
            const [apiEndpoint, resourceConfig] = routes[key] as ResourceTuple;
            routeMap[key] = createResourceFactory(resourceKlass, apiEndpoint, resourceConfig);

        } else if (isResourceConstructorObject(routes[key])) {
            const { apiEndpoint, ...resourceConfig } = routes[key] as ResourceConstructorObject;
            routeMap[key] = createResourceFactory(resourceKlass, apiEndpoint, resourceConfig);

        } else if (isObject(routes[key])) {
            routeMap[key] = createRouter(routes[key], null, resourceKlass, createResourceFactory);

        } else {
            const types = [
                'string',
                '[string, config]',
                '{apiEndpoint: string, ..config}',
                '{ ...any }',
            ];
            throw new Error(`Unknown type used "${key}", one of [${types.join(',')}] is allowed`);
        }
    });

export function serializeCookies(cookieVal: ObjectMap<string | null>) {
    /* istanbul ignore else: safeguard */
    if (isObject(cookieVal)) {
        // istanbul ignore next: Tested in package that implement Resource
        return Object.keys(cookieVal)
            .filter((key: string) => hasValue(cookieVal[key]))
            .map((key: string) => cookie.serialize(key, (cookieVal[key] as string)))
            .join('; ');
    }

    /* istanbul ignore next: safeguard */
    return null;
}

    test('mutateResponse functionally works', async () => {
        const res = new Resource('/hello', {
            apiRoot: hostUrl,
            mutateResponse(data: any, raw?: Response) {
                return {
                    data,
                    poweredBy: isObject(raw) ? raw.headers['x-powered-by'] : null,
                };
            },
        });

        await expectResponse(res.fetch(), { data: { message: 'world' }, poweredBy: 'Express' });
    });

                Object.keys(data).forEach((fieldKey) => {
                    const value = data[fieldKey];

                    // Future: Make this logic configurable
                    if (hasValue(value)) {
                        if (isArray(value)) {
                            // Send arrays as multipart arrays
                            value.forEach((fValue) => {
                                form.append(`${fieldKey}[]`, fValue);
                            });
                        } else if (isObject(value)) {
                            // Posting objects as stringifyed field contents to keep things consistent
                            form.append(fieldKey, JSON.stringify(value));
                        } else {
                            // Convert values via their toString
                            form.append(fieldKey, `${value}`);
                        }
                    }
                });

                Object.keys(data).forEach((fieldKey) => {
                    const value = data[fieldKey];

                    // Future: Make this logic configurable
                    if (hasValue(value)) {
                        if (isArray(value)) {
                            // Send arrays as multipart arrays
                            value.forEach((fValue) => {
                                req = req.field(`${fieldKey}[]`, fValue);
                            });
                        } else if (isObject(value)) {
                            // Posting objects as field contents is not supported by superagent
                            //  to work around this we just jsonify them
                            req = req.field(fieldKey, JSON.stringify(value));
                        } else {
                            // Convert values via their toString
                            req = req.field(fieldKey, `${value}`);
                        }
                    }
                });

export const isResourceTuple = (value: any): value is ResourceTuple => (
    isArray(value) && value.length === 2 && typeof value[0] === 'string' && isObject(value[1])
);

export const isResourceConstructorObject = (value: any): value is ResourceConstructorObject => (
    isObject(value) && 'apiEndpoint' in value
);