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Open source

config

Chai exposes a few options to change the library configuration.

Config optionDefaultDescription
truncateMsgThreshold300Check message length is truncated to this value.
truncateVariableThreshold100Variables interpolated into check message are truncated to this length. It prevents mistakes when the check name is very large, especially when aggregateChecks is false.
aggregateCheckstrueThe actual values are not interpolated into the check message. Disable for tests with 1 iteration.
logFailuresfalseWhen the check fails, debug messages are printed.
JavaScript 
import http from 'k6/http';
import chai, { describe, expect } from 'https://jslib.k6.io/k6chaijs/4.3.4.3/index.js';

// individual variables should be up to 20 chars after rendering.
chai.config.truncateVariableThreshold = 20;

// whole check() message must be below 300 chars.
chai.config.truncateMsgThreshold = 300;

// the variable values (resp.status) are inserted into the check message - useful for debugging or tests with 1 iteration
chai.config.aggregateChecks = false;

// when the check fails, WARN messages with variables are printed. Useful for debugging.
chai.config.logFailures = true;

export default function testSuite() {
  describe('Testing bad assertion.', () => {
    const response = http.get('https://test-api.k6.io/');

    expect(response.body).to.have.lengthOf.at.least(500);
  });
}

The resulting

Bash 
█ Testing bad assertion.
  ✓ expected '<!DOCTYPE html>\n<html lang="en">\n<hea...' to have property 'length'
  ✓ expected '<!DOCTYPE html>\n<html lang="en">\n<hea...' to have a length at least 500 got 15714