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no-weak-asymmetric-assertions

Disallow vacuous whole-value asymmetric assertions.

Rule detailsโ€‹

Asymmetric matchers are useful inside concrete expected shapes, but they become weak when they are the entire expected value. Assertions such as expect(result).toEqual(expect.anything()) or expect(result).toStrictEqual(expect.any(Object)) only prove broad existence or container type. They do not verify the expected domain value, shape, length, or state.

Incorrectโ€‹

it("returns a user", () => {
    expect(loadUser("abc")).toEqual(expect.anything());
});
it("returns a config object", () => {
    expect(loadConfig()).toStrictEqual(expect.any(Object));
});
it("returns a response subset", () => {
    expect(fetchResponse()).toMatchObject({});
});

Correctโ€‹

it("returns a user", () => {
    expect(loadUser("abc")).toEqual({
        id: "abc",
        name: expect.any(String),
    });
});
it("returns a config object", () => {
    expect(loadConfig()).toMatchObject({
        enabled: true,
    });
});

What this rule reportsโ€‹

This rule reports executable it(...) and test(...) callbacks that use whole-value asymmetric assertions or empty subset assertions that prove too little:

  • expect(value).toEqual(expect.anything())
  • expect(value).toEqual(expect.any(Object))
  • expect(value).toStrictEqual(expect.any(Array))
  • expect(value).toEqual(expect.arrayContaining([]))
  • expect(value).toEqual(expect.objectContaining({}))
  • expect(value).toMatchObject({})

Primitive field-level asymmetric checks such as expect(user).toEqual({ id: expect.any(String) }) remain valid because they sit inside a concrete expected shape.

Optionsโ€‹

This rule has no options.

When not to use itโ€‹

Disable this rule for smoke tests whose whole purpose is to verify that a value is broadly object-like. For most tests, assert at least one expected property, length, status, or exact value.

Rule catalog ID: R018