@yasuf I came up with a kind of explanation that it makes sure done will be called within 100ms, no matter whether axios.get is succeed or failed. Though you may think writing in a then next to catch can also achieve that, the current CI runs in about 2 mins, which means the time is not an emergency to consider.

@chinesedfan the timeout is to give the test a little bit of time to run. In that particular test, the get has to be performed and the catch block has to run (since that sets failure = true). Running the checks synchronously or with timeout 0 is too early to guarantee the axios part has time to run.

The tests probably should use Promise#finally:

      axios.get('http://localhost:4444/', {
        maxContentLength: 2000
      }).then(function (res) {
        success = true;
      }).catch(function (err) {
        error = err;
        failure = true;
      }).finally(function () {
        assert.equal(success, false, 'request should not succeed');
        assert.equal(failure, true, 'request should fail');
        assert.equal(error.message, 'maxContentLength size of 2000 exceeded');
        done();
      });

The problem is browser compatibility. For example, chrome 32+ support catch but finally requires chrome 63+

The tests probably should use Promise#finally

Exactly. And even a second then can act as finally without compatibility problems.

it makes sure done will be called within 100ms

I think that's the biggest advantage. If someone breaks axios to be never resolved or rejected, we don't need wait the case to timeout.