#prefer-strict-boolean-matchers

#Configuration

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

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

#Rule Details

Requires an assertion about a boolean to be spelled expect(value).toBe(true) or expect(value).toBe(false) rather than toBeTruthy() or toBeFalsy(). The truthiness matchers coerce whatever they are given, so '', 0, null and undefined all satisfy toBeFalsy(); asserting the literal keeps the test honest about the value it actually expects.

The matcher has to be called and has to be given nothing, since toBeTruthy and toBeFalsy take no arguments: expect(value).toBeTruthy asserts nothing and is left alone, and so is expect.toBeTruthy(), which never received a value to assert on. A matcher named by a computed key, expect(value)[matcherName](), is not reported either, because which assertion runs is only known at runtime. Chai's truthiness assertions are properties rather than matcher calls, and their strict form is equal(true), so expect(value).to.be.ok and expect(value).to.be.true are both outside this rule.

Modifiers are kept as written, so expect(value).not.toBeTruthy() becomes expect(value).not.toBe(true). That asserts something narrower than before — only the literal true is now rejected, rather than every truthy value — which is the assertion this rule is asking for.

This rule is the opposite of prefer-to-be-truthy and prefer-to-be-falsy, which rewrite in the other direction. Enable this one or those two, never both.

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('reports a valid configuration as valid', () => {
  expect(isValidConfig(config)).toBeTruthy();
});

#Correct

test('reports a valid configuration as valid', () => {
  expect(isValidConfig(config)).toBe(true);
});

#Autofix

Renames the matcher to toBe and writes the matching literal 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 — a comment between the parentheses stays put, with the literal inserted before it.