#no-error-equal

#Configuration

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

export default defineConfig([
  jestPlugin.configs.recommended,
  {
    rules: {
      'jest/no-error-equal': 'error',
    },
  },
]);

#Rule Details

Disallow using equality matchers on error types.

Jest's equality matchers compare errors mostly by their message. toEqual ignores the error type, so new TypeError('x') equals new RangeError('x'). toStrictEqual checks the type, but still ignores other properties such as code and cause. Passing an error instance to toThrow does not help either: toThrow(new Error('x')) compares only the message and passes even when the thrown value is not an Error.

Check the error type and the message separately instead. For a thrown error, pass the expected class to toThrow and assert the message in a second call. For an error value, use toBeInstanceOf and assert the properties you care about.

This rule reports toEqual and toStrictEqual assertions whose expect() subject has an Error type: the built-in Error, a built-in or user-defined class or interface that extends it, or a union whose members are all such types. It requires type information.

Examples of incorrect code for this rule:

expect(new AggregateError([], 'hello world')).toEqual(new Error('hello world'));

expect(new Error('hello world')).toStrictEqual('hello sunshine');

Examples of correct code for this rule:

expect(() => loadUser(id)).toThrow(NotFoundError);
expect(() => loadUser(id)).toThrow('user not found');

expect(error).toBeInstanceOf(AggregateError);
expect(error).toHaveProperty('message', 'hello world');

#Original Documentation

• eslint-plugin-jest: no-error-equal
• Source code