rejects.toThrow compares only against the message, not the error object

🐛 Bug Report or Feature Request

Unable to match on the object of the error of the rejected promise.

To Reproduce

await expect(axios(badUrl)).rejects.toThrow()

Expected behavior

Being able to access the error object and match on its objects.

await expect(axios(badUrl)).rejects.toThrow( (error) => error.reponse.status === 404)

Essentially I want to do this but without ES Lint yelling at me:

 try {
      await axios(url);
    } catch (error) {
      expect(error.response.status).toBe(404);
    }

[ericprud]

Nice! I played around with it a bit more and it turns out you need toMatchObject something which is NOT an Error:

const err = Promise.reject(new MyCustomError('Some Error', 'some value'))
await expect(err).rejects.toMatchObject(new MyCustomError('Some Error', 'other value')) // passes
await expect(err).rejects.toMatchObject({ message: 'Some Error', customProperty: 'other value' }) // fails

I recall this being because TS compiles Errors to something odd (at least before ES2015). I remember commenting on an issue or an SO to that effect but can’t find it now. [Edit: here’s one related TS issue]

I expanded my earlier tests (and fixed some labels) using your technique:

// Orphans and Children from two comments back
test(" pass       Orphan==Orphan",      () => {expect(o1a1).toMatchObject(o1a2);})
test(" fail       Orphan==Orphan",      () => {expect(o1a1).toMatchObject(o2a);})
test(" pass       Child ==Child ",      () => {expect(c1a1).toMatchObject(c1a2);})
test("!fail       Child ==Child ",      () => {expect(c1a1).toMatchObject(c2a);})
test(" fail       Child ==Child'",      () => {expect(c1a1).toMatchObject(Object.assign({}, c2a));})
test(" fail str(Child)==str(Child)",    () => {expect(JSON.stringify(c1a1)).toEqual(JSON.stringify(c2a));})
test(" pass async Child==Child ", async () => {await expect(Promise.reject(c1a1)).rejects.toMatchObject(c1a2);})
test("!fail async Child==Child ", async () => {await expect(Promise.reject(c1a1)).rejects.toMatchObject(c2a);})
test(" fail async Child==Child'", async () => {await expect(Promise.reject(c1a1)).rejects.toMatchObject(Object.assign({}, c2a));})

  ✓  pass       Orphan==Orphan (3 ms)
  ✕  fail       Orphan==Orphan (5 ms)
  ✓  pass       Child ==Child 
  ✓ !fail       Child ==Child  (1 ms)
  ✕  fail       Child ==Child' (1 ms)
  ✕  fail str(Child)==str(Child) (2 ms)
  ✓  pass async Child==Child  (1 ms)
  ✓ !fail async Child==Child 
  ✕  fail async Child==Child' (1 ms)

The '!'s flag the non-intuitive lack of failure caused but TSs special treatment of Errors and its subclasses.

[ericprud]

I agree that one can work around this but the jest expect package appears to throw away the thrown error, keeping only the message. This leads to counter-intuitive behavior like the OP’s or .toEqual(new MyHttpException(500, "b0rked")) accepting new MyHttpException(999, "b0rked")