no-async-foreach-assertions

Disallow async assertion callbacks passed to forEach in executable tests.

Rule details

Array.prototype.forEach ignores the promise returned by an async callback. In tests, that means assertions inside the callback can run after the test has already finished, or fail as an unhandled rejection instead of failing the test case that scheduled them.

Use a for...of loop when each check should run sequentially, or use await Promise.all(items.map(...)) when the checks can run in parallel.

Incorrect

it("checks every user", () => {
    users.forEach(async (user) => {
        await expect(loadProfile(user.id)).resolves.toMatchObject({
            id: user.id,
        });
    });
});

test("checks every token", async () => {
    tokens.forEach(async (token) => {
        const result = await validateToken(token);

        expect(result.valid).toBe(true);
    });
});

Correct

it("checks every user", async () => {
    for (const user of users) {
        await expect(loadProfile(user.id)).resolves.toMatchObject({
            id: user.id,
        });
    }
});

it("checks every user", async () => {
    await Promise.all(
        users.map(async (user) => {
            await expect(loadProfile(user.id)).resolves.toMatchObject({
                id: user.id,
            });
        })
    );
});

What this rule reports

This rule reports executable it(...) and test(...) callbacks that contain a forEach(...) call with an async callback whose directly executed body contains an expect(...) assertion. It also handles computed ["forEach"] access.

The rule does not report:

• synchronous forEach assertion callbacks;
• async forEach callbacks that do not contain assertions;
• assertions hidden inside nested helper function definitions;
• for...of loops or await Promise.all(items.map(...)) patterns.

Options

This rule has no options.

When not to use it

This rule is normally safe for Jest- and Vitest-style test suites. Disable it only for nonstandard test runners that deliberately capture promises returned by forEach callbacks, which regular JavaScript arrays do not do.

Rule catalog ID: R013