Jest gives no indication that test fails because of unhandled promise rejection.

🐛 Bug Report

When Jest fails a test for what it thinks - wrongly - is an unhandled rejection, it does not indicate this at all.

To Reproduce

This code in a test module causes Jest to wrongly think a promise rejection isn’t going to be handled.

describe("whatever", () => {
  it("fails for no reason", async () => {
    const p = Promise.reject(new Error("Shouldn't fail the test"));
    await new Promise(r => setTimeout(r, 100));
    await expect(p).rejects.toMatchObject({
      message: "Shouldn't fail the test",
    });
  });
});

Output:

 FAIL  src/test/plugging-in.test.ts
  DeviceManager - plugging and unplugging
    ○ skipped becomes useful after being plugged in
  whatever
    × fails for no reason (12ms)

  ● whatever › fails for no reason

    an error message

      90 | describe("whatever", () => {
      91 |   it("fails for no reason", async () => {
    > 92 |     const p = Promise.reject(new Error("an error message"));
         |                              ^
      93 |     await new Promise(r => setTimeout(r, 100));
      94 |     await expect(p).rejects.toMatchObject({
      95 |       message: "an error message",

      at Object.it (src/test/plugging-in.test.ts:92:30)

Test Suites: 1 failed, 1 total
Tests:       1 failed, 1 skipped, 2 total
Snapshots:   0 total
Time:        4.355s, estimated 6s
Ran all test suites matching /plugging-in/i with tests matching "whatever".

Note that nothing in the output conveys the real reason this test failed.

Expected behavior

Something in the output says that Jest failed the test because it can’t guarantee that the promise rejection will be handled. For instance, instead of:

     an error message

something like:

    Unhandled Promise Rejection:
    an error message

[korobochka]

I would also like to add that the problem here is not only “no indication”, but also the fact that the test fails: I was writing a test for utility function and I need to test that this function handles both successful and failing callbacks passed to it. Seems like the “negative” test fails for me anyway, even with expect(promise).rejects...., try/catch.

P.S. Also if I add const promise = Promise.reject('aaaa') to the top level in the file (outside describe) Jest will randomly fail first two tests. Very weird…

[timoxley]

@JoeLangewayClear’s workaround will suppress these errors, but it’s kind of like disabling the engine fault light in your car and claiming you “fixed it”