Implement expect.extend()

[Electroid]

https://jestjs.io/docs/expect#expectextendmatchers

import { expect } from "bun:test";

function toBeWithinRange(actual, floor, ceiling) {
  if (
    typeof actual !== 'number' ||
    typeof floor !== 'number' ||
    typeof ceiling !== 'number'
  ) {
    throw new Error('These must be of type number!');
  }

  const pass = actual >= floor && actual <= ceiling;
  if (pass) {
    return {
      message: () =>
        `expected ${this.utils.printReceived(
          actual,
        )} not to be within range ${this.utils.printExpected(
          `${floor} - ${ceiling}`,
        )}`,
      pass: true,
    };
  } else {
    return {
      message: () =>
        `expected ${this.utils.printReceived(
          actual,
        )} to be within range ${this.utils.printExpected(
          `${floor} - ${ceiling}`,
        )}`,
      pass: false,
    };
  }
}

expect.extend({
  toBeWithinRange,
});

[trnxdev]

I can try working on it!

UPD: after working on expect.extend, I realized that it was too hard to me. sorry for the time waste, but I just can't.

[mgasner]

fwiw, this is quite important if you're adopting bun (as we would like to do) with a significant base of existing tests that use the react testing library

[Electroid]

I can try working on it!

UPD: after working on expect.extend, I realized that it was too hard to me. sorry for the time waste, but I just can't.

It's all good, the Bun team is going to take this one.

[mgasner]

fwiw, this is quite important if you're adopting bun (as we would like to do) with a significant base of existing tests that use the react testing library

still!

[GuilhermeMGBR]

With support to extensions with extends any edge case that would take a while to be prioritized and added to bun could be implemented internally by the team wishing to adopt bun on their workflow.

[fatlard1993]

Not a perfect fix/workaround by any means, but for those looking for something before official support is added:

You can always use the standard expect assertions to use your matchers, Here's an example using @testing-library/jest-dom/matchers:

import { toBeVisible } from '@testing-library/jest-dom/matchers';
...
expect(toBeVisible(getByRole(container, 'combobox')).pass).toBe(true);

VS

import * as matchers from '@testing-library/jest-dom/matchers';
...
expect.extend(matchers);
...
expect(getByRole(container, 'combobox')).toBeVisible();

[Jarred-Sumner]

Implemented by @otgerrogla in #7319

This will ship with Bun v1.0.15, which will either release later tonight or tomorrow.

To upgrade to the canary build:

bun upgrade --canary