express supertest / superagent utility for accessing response cookies as objects

extract-cookies.js

const shapeFlags = flags =>
  flags.reduce((shapedFlags, flag) => {
    const [flagName, rawValue] = flag.split("=");
    // edge case where a cookie has a single flag and "; " split results in trailing ";"
    const value = rawValue ? rawValue.replace(";", "") : true;
    return { ...shapedFlags, [flagName]: value };
  }, {});

const extractCookies = headers => {
  const cookies = headers["set-cookie"]; // Cookie[]

  return cookies.reduce((shapedCookies, cookieString) => {
    const [rawCookie, ...flags] = cookieString.split("; ");
    const [cookieName, value] = rawCookie.split("=");
    return { ...shapedCookies, [cookieName]: { value, flags: shapeFlags(flags) } };
  }, {});
};

module.exports = {
  shapeFlags,
  extractCookies,
};

extract-cookies.test.js

const { extractCookies, shapeFlags } = require("../extract-cookies");

const sampleHeaders = {
  vary: "Origin",
  "access-control-allow-credentials": "true",
  "set-cookie": [
    "refresh_token=s%3AeyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJVMkZzZEdWa1gxOVBEL0RqVUlXV2lvUmZhWlhuWWdJTExaUGJ2cW4xcWRVPSIsImlhdCI6MTU2MjIwMTAzNywiZXhwIjoxNTYyODA1ODM3LCJpc3MiOiJsb2NhbGhvc3QiLCJqdGkiOiI5MmQzMmY4Ni05ZmYzLTQ5OTgtOWE1Zi1jZDNkZWU1YTRmYmQifQ.6omhdrHChv4cPhfhvwz6xMK7RPsc-SCtWxHTIkBLRrw.kaJG83X6V9YBHwYPlCQ61X7KOsX7wFSfD7hnEdP0pmg; Domain=localhost; Path=/tokens; HttpOnly; SameSite=Strict",
  ],
  etag: 'W/"a-bAsFyilMr4Ra1hIU5PyoyFRunpI"',
  date: "Thu, 04 Jul 2019 00:43:57 GMT",
  connection: "close",
};

describe('shapeFlags: shapes an array of ["Flag=Value"] pairs into an object', () => {
  const [cookie, ...flags] = sampleHeaders["set-cookie"][0].split("; ");
  const output = shapeFlags(flags);

  test("returns an object of { flag: value } entries", () =>
    Object.entries({
      Domain: "localhost",
      Path: "/tokens",
      HttpOnly: true,
      SameSite: "Strict",
    }).forEach(flagEntry => {
      const [flagName, expectedValue] = flagEntry;
      expect(output[flagName]).toBe(expectedValue);
    }));

  test("sets value to true for flags without values (boolean flags)", () => {
    expect(output.HttpOnly).toBe(true);
  });

  test('given a cookie with a single flag strips the trailing ";" character', () => {
    const singleFlagHeaders = {
      "set-cookie": ["cookiename=cookievalue; Domain=oneflag"],
    };
    const [cookie, ...flags] = singleFlagHeaders["set-cookie"][0].split("; ");
    expect(shapeFlags(flags)).toEqual({ Domain: "oneflag" });
  });
});

describe("extractCookies: extracts and shapes response cookies from the set-cookie header", () => {
  const output = extractCookies(sampleHeaders);

  test("returns an object of { cookieName: { value, flags } } shape", () => {
    expect(output.refresh_token).toBeDefined();
    expect(output.refresh_token.value).toBeDefined();
    expect(output.refresh_token.flags).toBeDefined();
  });

  test("extracts the value of a given cookie", () => {
    expect(output.refresh_token.value).toBe(
      "s%3AeyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJVMkZzZEdWa1gxOVBEL0RqVUlXV2lvUmZhWlhuWWdJTExaUGJ2cW4xcWRVPSIsImlhdCI6MTU2MjIwMTAzNywiZXhwIjoxNTYyODA1ODM3LCJpc3MiOiJsb2NhbGhvc3QiLCJqdGkiOiI5MmQzMmY4Ni05ZmYzLTQ5OTgtOWE1Zi1jZDNkZWU1YTRmYmQifQ.6omhdrHChv4cPhfhvwz6xMK7RPsc-SCtWxHTIkBLRrw.kaJG83X6V9YBHwYPlCQ61X7KOsX7wFSfD7hnEdP0pmg",
    );
  });

  test("extracts and shapes the flags of the cookie", () => {
    const [cookie, ...flags] = sampleHeaders["set-cookie"][0].split("; ");
    expect(output.refresh_token.flags).toEqual(shapeFlags(flags));
  });

  test("cookie has no additional flags: cookieName.flags is an empty object", () => {
    const noFlagsHeaders = {
      "set-cookie": [
        "refresh_token=s%3AeyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJVMkZzZEdWa1gxOVBEL0RqVUlXV2lvUmZhWlhuWWdJTExaUGJ2cW4xcWRVPSIsImlhdCI6MTU2MjIwMTAzNywiZXhwIjoxNTYyODA1ODM3LCJpc3MiOiJsb2NhbGhvc3QiLCJqdGkiOiI5MmQzMmY4Ni05ZmYzLTQ5OTgtOWE1Zi1jZDNkZWU1YTRmYmQifQ.6omhdrHChv4cPhfhvwz6xMK7RPsc-SCtWxHTIkBLRrw.kaJG83X6V9YBHwYPlCQ61X7KOsX7wFSfD7hnEdP0pmg;",
      ],
    };

    const output = extractCookies(noFlagsHeaders);
    expect(output.refresh_token.flags).toEqual({});
  });

  test("supports multiple cookie entries", () => {
    const multipleCookiesHeaders = {
      "set-cookie": [
        "someothercookie=cookievalue; Domain=test;",
        "refresh_token=s%3AeyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJVMkZzZEdWa1gxOVBEL0RqVUlXV2lvUmZhWlhuWWdJTExaUGJ2cW4xcWRVPSIsImlhdCI6MTU2MjIwMTAzNywiZXhwIjoxNTYyODA1ODM3LCJpc3MiOiJsb2NhbGhvc3QiLCJqdGkiOiI5MmQzMmY4Ni05ZmYzLTQ5OTgtOWE1Zi1jZDNkZWU1YTRmYmQifQ.6omhdrHChv4cPhfhvwz6xMK7RPsc-SCtWxHTIkBLRrw.kaJG83X6V9YBHwYPlCQ61X7KOsX7wFSfD7hnEdP0pmg;",
      ],
    };

    const output = extractCookies(multipleCookiesHeaders);

    ["refresh_token", "someothercookie"].forEach(cookieName =>
      expect(output[cookieName]).toBeDefined(),
    );

    expect(output.someothercookie.value).toBe("cookievalue");
    expect(output.someothercookie.flags).toEqual({ Domain: "test" });
  });
});

usage

const app = require('./app');
const request = require('supertest');
const { extractCookies } = require('./utils/extract-cookies');

test('some test needing cookie details', async () => {
  const res = await request(app).post('/tokens', { ...data });
  const cookies = extractCookies(res.headers); // or res.header alias
  // do tests on cookies, cookies.cookieName.[value, flags.[flagName]]
});

wrote this because parsing the res.headers[set-cookie] is a pain in the ass when needing to verify that cookies were set properly. extracts the set-cookie header from an express response using supertest and provides an object of the following shape:

const cookies = {
  cookieName: {
    value: 'cookie value',
    flags: {
      flagName: 'flag value',
      booleanFlag: true, // boolean flags (no value) are given true as their value
    },
  },
};

In case anyone is looking for a Typescript version of this

/**
 * Format the cookie flags
 *
 * @example
 * ```
 * { Path: '/', Secure: true, SameSite: 'Lax' }
 * ```
 */
const shapeFlags = (flags: Array<string>) =>
  flags.reduce((shapedFlags, flag) => {
    const [flagName, rawValue] = flag.split('=');
    // edge case where a cookie has a single flag and "; " split results in trailing ";"
    const value = rawValue ? rawValue.replace(';', '') : true;
    return { ...shapedFlags, [flagName]: value };
  }, {});

/**
 * The interface for structure in which a cookie is
 * returned by `extractCookies`
 */
interface ExtractedCookie {
  value: string;
  flags: Record<string, string | boolean | number>;
}

/**
 * Extract cookies from headers
 *
 * @param headers The headers of the response
 *
 * @reference https://gist.github.com/the-vampiire/a564af41ed0ce8eb7c30dbe6c0f627d8
 */
export const extractCookies = (
  headers: Record<string, string | Array<string | number>>
): Record<string, ExtractedCookie> => {
  const cookies = headers['set-cookie'] as Array<string>;

  return cookies.reduce((shapedCookies, cookieString) => {
    const [rawCookie, ...flags] = cookieString.split('; ');
    const [cookieName, value] = rawCookie.split('=');
    return { ...shapedCookies, [cookieName]: { value, flags: shapeFlags(flags) } };
  }, {});
};