#prefer-called-times

#Configuration

import { defineConfig, rstestPlugin } from '@rslint/core';

export default defineConfig([
  rstestPlugin.configs.recommended,
  {
    rules: {
      'rstest/prefer-called-times': 'error',
    },
  },
]);

#Rule Details

Requires call-count assertions to be spelled expect(fn).toHaveBeenCalledTimes(1) rather than expect(fn).toHaveBeenCalledOnce(). Both assert the same thing, and writing the count out keeps every call-count assertion in a file in one form, so changing an expected count becomes an edit to a number instead of a switch to a different matcher.

The matcher has to be called. expect(fn).toHaveBeenCalledOnce asserts nothing, so it is left alone, and so is expect.toHaveBeenCalledOnce(), which never received a value to count calls on. A matcher named by a computed key, expect(fn)[matcherName](), is not reported either, because which assertion runs is only known at runtime. Chai's calledOnce is a property rather than a matcher call, and the assertion that takes a count in that style is callCount(1), so expect(fn).to.have.been.calledOnce is outside this rule.

Every expect source is recognized: globals, named and renamed imports, require destructuring, namespace imports, whole-module require, import.meta.rstest, Playwright integrations, and the expect a test callback receives through its TestContext. An expect from another assertion library, or a local variable that shadows expect, is not reported.

#Incorrect

test('notifies the listener once', () => {
  emitter.emit('ready');

  expect(listener).toHaveBeenCalledOnce();
});

#Correct

test('notifies the listener once', () => {
  emitter.emit('ready');

  expect(listener).toHaveBeenCalledTimes(1);
});

#Autofix

Renames the matcher to toHaveBeenCalledTimes and inserts the count 1 into its argument list. Nothing else in the assertion changes: the expect root as written at the call site, expect.soft, the second message argument of expect(actual, message), the modifier chain, the accessor's own quoting, and the surrounding line breaks and comments are all left as they are.