bun:test/prefer-comparison-matcher

expect(price < 100).toBe(true) compares first and hands expect only the result. When it fails, the message says that false isn't true, and you don't see the price. expect(price).toBeLessThan(100) prints both numbers.

The rule reports >, >=, < and <= inside expect() when the result is checked against true or false with toBe(), toEqual() or toStrictEqual().

--fix-suggestions rewrites the assertion. --fix doesn't, because the comparison matchers throw on anything that isn't a number or a bigint.

Configure#

Off by default. To turn it on:

[lint.rules]
"bun:test/prefer-comparison-matcher" = "error" # or "warn"

Examples#

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

test("applies the discount", () => {
  const price = discounted(100);
  expect(price < 100).toBe(true);
  expect(price < 0).toBe(false);
});

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

test("applies the discount", () => {
  const price = discounted(100);
  expect(price).toBeLessThan(100);
  expect(price).toBeGreaterThanOrEqual(0);
});

The comparison matchers only take numbers and bigints, so a comparison with a string literal or a template literal is left alone:

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

test("sorts after the first entry", () => {
  expect(lastName() > "Adams").toBe(true);
});

When not to use it#

The rule doesn't look at types, so it also reports comparisons of dates, or of strings held in variables. The comparison matchers throw on those values. This test is correct as written:

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

test("renewing extends the subscription", () => {
  expect(renewed.expiresAt > current.expiresAt).toBe(true);
});