bun:test/prefer-expect-type-of

expect(typeof value).toBe("string") only gives expect the name of the type. When the test fails, the output compares "number" with "string" and doesn't show the value. expect(value).toBeTypeOf("string") shows it.

The rule reports typeof inside expect with toBe or toEqual, with or without .not.

--fix rewrites the assertion.

Configure#

Off by default. To turn it on:

[lint.rules]
"bun:test/prefer-expect-type-of" = "error" # or "warn"

Examples#

import { expect, test } from "bun:test";

test("the user has a name", () => {
  expect(typeof user.name).toBe("string");
  expect(typeof user.save).not.toEqual("undefined");
});

import { expect, test } from "bun:test";

test("the user has a name", () => {
  expect(user.name).toBeTypeOf("string");
  expect(user.save).not.toBeTypeOf("undefined");
});