Props comparison regression in 1.1.3 (and later)

[BeeMargarida]

Subject of the issue

After the release of 1.1.3, some tests related to props comparison started to fail. For example a test similar to the one below resulted in

AssertionError [ERR_ASSERTION]: Values have same structure but are not reference-equal:
[
  'Q',
  'W',
  'E',
  'R',
  'T',
  'Y',
  'U',
  'I',
  'O',
  'P'
]

Steps to reproduce

const assert = require("assert");
const testUtils = require("@vue/test-utils");
const components = require("./components");

it("should have valid characters set", () => {
        const component = testUtils(components["Keyboard"], {
            propsData: { keys: ["Q", "W", "E", "R", "T", "Y", "U", "I", "O", "P"] }
        });
        assert.deepStrictEqual(component.vm.$props.keys, [
            "Q",
            "W",
            "E",
            "R",
            "T",
            "Y",
            "U",
            "I",
            "O",
            "P"
        ]);
    });

Expected behaviour

It should result in a valid comparison.

Actual behaviour

The test fails while comparing the same array.

Possible Solution

I checked the diff between the 1.1.2 and 1.1.3 (v1.1.2...v1.1.3) and some changes were made to create-instance.js and wrapper.js. I suspect the regression was introduced there.

[BeeMargarida]

Update:
I tried to simulate a similar test in vue-test-utils, and it seems the problem is related with deepStrictEqual of assert, since with jasmine it seems to be working.

Test:

it('test', () => {
    const TestComponent = {
        template: `
          <div>
            {{ array }}
          </div>'
        `,
        props: {
            keys: {
                type: Array,
                required: true
            }
        },
        name: "test-component"
    }
    const wrapper = mountingMethod(TestComponent, {
      propsData: { keys: ["Q", "W", "E", "R", "T", "Y", "U", "I", "O", "P"] }
    });
    expect(wrapper.props('keys')).toEqual(["Q", "W", "E", "R", "T", "Y", "U", "I", "O", "P"])
    expect(wrapper.vm.$props.keys).toEqual(["Q", "W", "E", "R", "T", "Y", "U", "I", "O", "P"])
    deepStrictEqual(wrapper.props('keys'), ["Q", "W", "E", "R", "T", "Y", "U", "I", "O", "P"])
  })

Result:

[lmiller1990]

So - is there an actual regression here? Seems like this is on the assertion library's side (if I understood correctly).

If there is an actual bug, best thing to do is make a PR adding your test case, then we can fix it.

[BeeMargarida]

@lmiller1990 I'm sorry, I ended up forgetting about this. I made some experiences and opened a PR with some explanation: #1850. TLDR: the problem is not in the assertion library, but I still don't know what introduced the problem (still investigating)