Jest: objectContaining should be recursive but isn't

[BuckAMayzing]

🐛 Bug Report

I couldn't find a duplicate of this, even though it seems like something that could have come up before. The closest I found was #10186, which is related, but only tangentially.

expect.objectContaining does not work recursively as docs state.

To Reproduce

Here's a small test that will fail:

it('testy test test', () => {
  const expected = {
    a: 1,
    subProps: {
      someArray: [1],
    },
  }

  const received = {
    a: 1,
    subProps: {
      someArray: [1],
      someOtherArray: [],
    },
  }

  expect(received).toEqual(expect.objectContaining(expected))
})

Expected behavior

The test above should have passed according to the docs.

Link to repl or repo (highly encouraged)

Passing and failing tests here

envinfo

doesn't appear to be environment specific - repl and local machines both reproduce. I can add mine and repl's if it seems to be necessary.

workaround

use toMatchObject instead (which incidentally seems to have a nicer api)

additional info

If we look at toMatchObject vs objectContaining, the customTesters passed to the equals function differ - it looks like toMatchObject is actually true subset equality where objectContaining is only subset equality for the first level in the object - in this loop, recursion isn't happening.

Looks like there are two options to fix this: either objectContaining can implement a recursive asymmetricMatch, or it can share a code path with toMatchObject, since the two appear to be trying to accomplish the same goal (unless I'm missing something). The latter seems easier, at least on the surface, but I've not looked into it deeply.

It also looks like #10430 could potentially replace this fix, and objectContaining could become deprecated in favor of toMatchObject.

[ioancole]

PR facebook/jest#10508 should fix this.

In the meantime, if you want the objectContaining behavior that you describe, you should also wrap expected-result sub-objects in objectContaining. The following test should pass:

it('testy test test', () => {
  const expected = expect.objectContaining({
    a: 1,
    subProps: expect.objectContaining({
      someArray: [1],
    }),
  });

  const received = {
    a: 1,
    subProps: {
      someArray: [1],
      someOtherArray: [],
    },
  };

  expect(received).toEqual(expected);
});

Or, of course, just use toMatchObject...