Jest - how to expect for a thrown error on an async function, which gets caught

Question

I try to do this:

it('should throw an error', async ()=> {
    expect.assertions(1);
    try {
        await processor({}, MODULE_CONFIG)
    }
    catch (e) {
        expect(e).toBe("[TypeError: Cannot read properties of undefined (reading 'match')]")
    }
});

but it gives me this error:

I tried toMatch like in the docs, but it also give an error (one that seems even worse)

I tried using rejects.tobe instead, but i get the same error:

This is maybe a duplicate of this question https://stackoverflow.com/questions/50821835/how-do-i-properly-test-for-a-rejected-promise-using-jest/64474313#64474313 — Andres Gardiol, Jun 30 '22 at 15:27
Does this answer your question? [How do I properly test for a rejected promise using Jest?](https://stackoverflow.com/questions/50821835/how-do-i-properly-test-for-a-rejected-promise-using-jest) — Andres Gardiol, Jun 30 '22 at 15:27
Try to use: expect(e).toThrow(TypeError) https://stackoverflow.com/questions/46042613/how-to-test-the-type-of-a-thrown-exception-in-jest — Mayker Miyanaga, Jun 30 '22 at 17:10

score 2 · Answer 1 · answered Jul 01 '22 at 12:34

Your problem is with what you are trying to assert

I'm assuming that you are throwing an error from processor

If you are, and you are asserting what that error is, keep in mind that typeof e === object, not string

For example:

function iThrownAnError() {
  throw new Error("ups");
}

describe("test a function that throws an error", () => {
  it("catches an error as expected", () => {
    try {
      iThrownAnError();
    } catch (e) {
      console.log(typeof e); // logs object
      console.log(typeof "ups"); // logs string

      // the test pass
      expect(e).toStrictEqual(new Error("ups"));

      // the test would fail
      // Expected: "ups"
      // Received: [Error: ups]
      expect(e).toStrictEqual("ups");
    }
  });
});

score -1 · Accepted Answer · answered Jul 01 '22 at 17:55

-1

The best answer I found seems to be getting the message property from the error (which is essentially just the error as a string), and comparing that.

expect(e.message).toBe("Cannot read properties of undefined (reading 'match')")

answered Jul 01 '22 at 17:55

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Jest - how to expect for a thrown error on an async function, which gets caught

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