Supertest should report response body on error

[phil294]

Since #95 got closed 6 years ago and there seems to be no incentive to reopen this, here's an almost 1:1 copy of that issue, but instead of reporting the hard coded .error property, imo the entire response body should be printed out, as currently the server response is disregarded completely.

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At the moment when the status message does not match the expectations we get an error message like: expected 200 "OK, got 500 Internal server error It would be helpful to display a server custom error message if any, as defined by: res.send(500, { error: 'something blew up' }); would display: expected 200 "OK", got 500 with response "{ error: 'something blew up' }"

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+1, but maybe we should just add the contents of res.body. It should contain the relevant error messages that would help devs figure out what the errors are.

[nickbclifford]

+1, found myself wishing for this today.

[lucaswoj]

It's a bit complex, but I've worked around this by defining a custom jest matcher

expect.extend({
  toBeOk(response: Response) {
    if (response.ok) {
      return {
        message: () => 'Ok',
        pass: true,
      };
    } else {
      return {
        message: () => {
          const request = response.request;
          // Format the request and response as CURL output for debugging.
          return [
            `> ${request.method} ${request.url} HTTP/1.1`,
            formatHeaders('> ', request.headers),
            `< HTTP/1.1 ${response.status}`,
            formatHeaders('< ', response.headers),
            response.text,
          ]
            .filter(Boolean)
            .join('\n');
        },
        pass: false,
      };
    }
  },
});
function formatHeaders(
  prefix: string,
  headers: Response['headers'] | Response['request']['headers'] | undefined | null,
) {
  if (!headers) return undefined;
  const entries =
    headers instanceof Headers ? Array.from(headers.entries()) : Object.entries(headers);
  entries.map(([key, value]) => `${prefix}${key}: ${value}`).join('\n');
}

and corresponding jest.d.ts

declare global {
  namespace jest {
    interface Matchers<R> {
      toBeOk(): R;
    }
  }
}
export {};

It can be used as

expect(response).toBeOk();