CODEWITHSUNDEEP
javascriptjestjs
Leff
Leff

Reputation: 1360

Jest - Testing function that throws an error not working

I have a simple function that throws error if input is lower than 0:

export const hoursMinutesSecondsFromSeconds = (inputSeconds) => {
  if (inputSeconds < 0) {
    throw new Error('illegal inputSeconds < 0');
  }
  let rem = Math.abs(inputSeconds);
  let divisor = 3600;
  const result = [];
  while (divisor >= 1) {
    result.push(Math.floor(rem / divisor));
    rem = rem % divisor;
    divisor = divisor / 60;
  }
  return result;
};

I am trying to test this function with an input that is lower than 0, like this:

import { hoursMinutesSecondsFromSeconds } from './timetools';

describe('hoursMinutesSecondsFromSeconds', () => {
  it('throws error', () => {
    expect(hoursMinutesSecondsFromSeconds(-2)).toThrowError('illegal inputSeconds < 0');
  });
});

But, when I run this test, the test fails and I get an error message:

Error: illegal inputSeconds < 0

Why is this not passing the test, when it throws an error exactly like I am expecting it to throw in my test?

Upvotes: 1

Views: 261

Answers (2)

Ben Stephens
Ben Stephens

Reputation: 3371

Looking at: https://jestjs.io/docs/en/expect#tothrowerror I expect that you need to wrap your function call in a function.

Like:

expect(() => {
    hoursMinutesSecondsFromSeconds(-2);
}).toThrowError('illegal inputSeconds < 0');

Upvotes: 1

Estus Flask
Estus Flask

Reputation: 223104

It's impossible in JavaScript to handle an error that was thrown like expect(hoursMinutesSecondsFromSeconds(-2)) without wrapping it with try..catch.

toThrowError is supposed to be used with a function that is internally wrapped with try..catch when it's called. It should be:

expect(() => hoursMinutesSecondsFromSeconds(-2)).toThrowError('illegal inputSeconds < 0');

Upvotes: 1

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