bun:test/no-unneeded-async-expect-function

.rejects and .resolves work on a promise. bun test doesn't call a function for them, so an async function in expect fails with Expected promise. Pass the call itself.

--fix replaces the function with the call. It leaves a function that has a comment in it alone, because the comment would be lost.

Configure#

Off by default. To turn it on:

[lint.rules]
"bun:test/no-unneeded-async-expect-function" = "error" # or "warn"

Examples#

import { expect, test } from "bun:test";

test("rejects an empty name", async () => {
  await expect(async () => {
    await saveUser({ name: "" });
  }).rejects.toThrow("name is required");

  await expect(async () => await saveUser({ name: "" })).rejects.toThrow();
});

import { expect, test } from "bun:test";

test("rejects an empty name", async () => {
  await expect(saveUser({ name: "" })).rejects.toThrow("name is required");
});

Without .rejects or .resolves the function is needed, so it isn't reported. toThrow calls it and waits for its promise. Given the promise itself, it fails with Expected value must be a function:

import { expect, test } from "bun:test";

test("rejects an empty name", () => {
  expect(async () => {
    await saveUser({ name: "" });
  }).toThrow("name is required");
});

That form also catches an error that the call throws before it returns a promise. Without the function, such an error is thrown before expect runs.