vitest/prefer-called-once

toHaveBeenCalledTimes(1) and toHaveBeenCalledOnce() assert the same thing. This rule picks the shorter one, so the whole project writes it the same way. The aliases are covered too, so toBeCalledTimes(1) becomes toBeCalledOnce().

--fix rewrites the matcher.

Configure

Off by default. To turn it on:

[lint.rules]
"vitest/prefer-called-once" = "error" # or "warn"

Examples

Reported:

import { expect, test, vi } from "vitest";

test("notifies the listener", () => {
  const listener = vi.fn();
  publish("ready", listener);
  expect(listener).toHaveBeenCalledTimes(1);
});

Not reported:

import { expect, test, vi } from "vitest";

test("notifies the listener", () => {
  const listener = vi.fn();
  publish("ready", listener);
  expect(listener).toHaveBeenCalledOnce();

  publish("done", listener);
  expect(listener).toHaveBeenCalledTimes(2);
});

When not to use it

vitest/prefer-called-times asks for the opposite. Turn on one of the two, not both.