False positive behavior toStrictEqual

[sirian]

🐛 Bug Report

.toStrictEqual doesn't perform === equality check for nested objects

To Reproduce

test("", () => {
    class Foo {}
    class Bar {}

    const p1 = new class A extends Foo{}();
    const p2 = new class A extends Bar{}();

    expect([p1]).toStrictEqual([p1]); // pass
    expect([p1]).toStrictEqual([p2]) // pass, but should not
});

Expected behavior

expect([p1]).toStrictEqual([p2]) should not pass

[SimenB]

It's not ===, it's equality. UsetoBe for referential equality.

PR welcome if you think the docs can be improved :)

[SimenB]

@rickhanlonii I see you asked OP to open this. Why do you think it's a bug?

[sirian]

@SimenB more attention pls. I'm talking about array values equality rather than arrays itself.
Look at #6757 (comment)

[SimenB]

Right. Still, your example is supposed to pass, it's not a bug. 2 instances of the same class are considered equal

[sirian]

@SimenB ok. But is there any way to perform deep/iterable toBe check?

For example to test memoizing.

Of course i could use loops like below or create custom matcher, but it will display bad errors.
Look

test("", () => {

    class HugeFoo {
        @memoize
        static huge(){}
    }

    function hugeTask() {
        return [10, HugeFoo.huge()]
    }

    const a1 = hugeTask();
    const a2 = hugeTask();
    expect(a1).toEqual(a2); 
    expect(a1).toStrictEqual(a2);

    expect(a1.length).toBe(a2.length);
    for (let i = 0; i < a1.length; i++) {
        expect(a1[i]).toBe(a2[i]);
    }
});

[SimenB]

@mattphillips are there any matchers for this in jest-extended?

[rickhanlonii]

2 instances of the same class are considered equal

Ah, my mistake

[sirian]

@rickhanlonii nevertheless bug exists when comparing 2 instances of different classes with identical name.
#6767

[sirian]

@rickhanlonii @SimenB
i think non-plain objects should be compared with === and not by structure. At least sentence 2 instances of the same class are considered equal is controversial new Boolean(true) and new Boolean(false) are instances of same class. so they should be considered equal?

[sirian]

@SimenB
Also toStrictEqual is ambiguous. From documentation

Use .toStrictEqual to test that objects have the same types as well as structure.

const object = Object(1);

expect(object).toStrictEqual(1); 
// pass, but should not - they have different types.
// typeof object !== typeof 1

expect(new Number(1)).toStrictEqual(new Number(2)); 
// fail, but they have same structure, and same type

[github-actions]

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