vitest/prefer-called-once

Require toHaveBeenCalledOnce() instead of toHaveBeenCalledTimes(1)

fixable

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:

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

Examples#

example.ts1 problem
import { expect, test, vi } from "vitest";

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