expect("エ").toEqual("ア") does not throw Error

[shigurenimo]

What version of Bun is running?

1.1.30

What platform is your computer?

Darwin 24.0.0 arm64 arm

What steps can reproduce the bug?

1. make empty directory
2. run bun init
3. make a test file index.test.ts
4. run bun test

What is the expected behavior?

should be

✗ toEqual [3.75ms]
3 | test("toEqual", () => {
4 |   expect("エ").toEqual("ア")
5 | })
6 | 
7 | test("toBe", () => {
8 |   expect("エ").toBe("ア")
                  ^
error: expect(received).toBe(expected)

Expected: "ア"
Received: "エ"

What do you see instead?

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

test("toEqual", () => {
  expect("ア").toEqual("ア")
})

test("toBe", () => {
  expect("a").toBe("ア")
})

$ bun test
bun test v1.1.30-canary.37 (117e1b38)

index.test.ts:
✓ toEqual
✓ toBe [1.04ms]

 2 pass
 0 fail
 2 expect() calls
Ran 2 tests across 1 files. [9.00ms]

Additional information

I had to use Katakana in my project. the cause is Katakana?

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

test("Katakana and Alphabet", () => {
  expect("ア").toEqual("a") // fail
})

test("Alphabet and Katakana", () => {
  expect("a").toEqual("ア") // fail
})

test("Katakana and Katakana", () => {
  expect("フ").toEqual("ア") // pass
})

test("Kanji and Katakana", () => {
  expect("了").toEqual("ア") // fail
})

[dylan-conway]

This is most likely bug in our diff formatter. It is appending invalid UTF-8 sequences, which will error when we try to create the error message with WTF::String::fromUTF8, which will then fail to create the error for toEqual

[shigurenimo]

to avoid this problem, it's possible to use an array for now.

expect(["エ"]).toEqual(["ア"])