vitest/prefer-to-be-object

expectTypeOf() has its own matcher for object types, toBeObject(). toBeInstanceOf(Object) and an instanceof Object check are longer ways to ask the same question.

The rule only checks expectTypeOf(). expect(value).toBeInstanceOf(Object) isn't reported.

--fix rewrites the assertion to toBeObject(), or to .not.toBeObject() if the original tested for the opposite.

Configure

Off by default. To turn it on:

[lint.rules]
"vitest/prefer-to-be-object" = "error" # or "warn"

Examples

Reported:

import { expectTypeOf, test } from "vitest";

test("the config is an object", () => {
  const config = loadConfig();
  expectTypeOf(config).toBeInstanceOf(Object);
  expectTypeOf(config instanceof Object).toBeTruthy();
  expectTypeOf(config.name instanceof Object).toBeFalsy();
});

Not reported:

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

test("the config is an object", () => {
  const config = loadConfig();
  expectTypeOf(config).toBeObject();
  expectTypeOf(config.name).not.toBeObject();
  expectTypeOf(config.createdAt).toBeInstanceOf(Date);
  expect(config).toBeInstanceOf(Object);
});