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expect.configure()

The expect.configure() method creates a new configured expect instance with custom behavior for the k6 testing library, including timeouts, display options, and soft assertion behavior.

This new instance can be used in place of the default expect function, and will apply the specified configuration to all assertions made with it.

The imported expect instance remains unchanged and continues to use the default configuration, allowing different assertion configurations to co-exist within a test.

Syntax

JavaScript 
const configuredExpect = expect.configure(options);

Parameters

ParameterTypeDescription
optionsobjectConfiguration options object

Options

PropertyTypeDefaultDescription
timeoutnumber5000Default timeout in milliseconds for retrying assertions
intervalnumber100Polling interval in milliseconds for retrying assertions
colorizebooleantrueEnable colorized output in assertion messages
displaystring"pretty"Output format for assertion messages ("pretty" or "inline")
softModestring"fail"Soft assertion behavior ("fail" or "throw")

Returns

TypeDescription
ExpectA new expect instance with the specified configuration

Timeout configuration

The timeout option controls how long retrying assertions will wait for a condition to become true:

JavaScript 
import { expect } from 'https://jslib.k6.io/k6-testing/0.5.0/index.js';

// Create a configured expect instance with longer timeout for slow-loading elements
const slowExpect = expect.configure({
  timeout: 10000, // 10 seconds
  interval: 500, // Check every 500ms
});

Display Options

The display and colorize options control how assertion failures are reported:

JavaScript 
import { expect } from 'https://jslib.k6.io/k6-testing/0.5.0/index.js';

// Create expect instance with inline output and no colors
const inlineExpect = expect.configure({
  display: 'inline',
  colorize: false,
});

Soft Assertion Mode

The softMode option controls whether failed assertions stop test execution:

JavaScript 
import { expect } from 'https://jslib.k6.io/k6-testing/0.5.0/index.js';

// The default behavior of soft assertions is mark the test as failed, the `softMode` option
// allows to configure soft assertions to throw an exception and fail the current iteration instead.
const softExpect = expect.configure({
  softMode: 'throw',
});

Environment Variables

Configuration options can also be set using environment variables:

Environment VariableOptionDescription
K6_TESTING_TIMEOUTtimeoutDefault timeout in milliseconds
K6_TESTING_INTERVALintervalPolling interval in milliseconds
K6_TESTING_COLORIZEcolorizeEnable colored output (true/false)
K6_TESTING_DISPLAYdisplayOutput format (pretty/inline)
K6_TESTING_SOFT_MODEsoftModeSoft assertion mode (fail/throw)
bash 
# Set environment variables
export K6_TESTING_TIMEOUT=10000
export K6_TESTING_SOFT_MODE=throw
k6 run test.js

Examples

Basic Configuration

JavaScript 
import { expect } from 'https://jslib.k6.io/k6-testing/0.5.0/index.js';

// Create a configured expect instance
const myExpect = expect.configure({
  timeout: 8000,
  interval: 200,
  colorize: true,
  display: 'pretty',
});

export default function () {
  // Use the configured instance
  myExpect(response.status).toBe(200);

  // Original expect instance still works with defaults
  expect(response.status).toBe(200);
}

Browser Testing Configuration

JavaScript 
import { browser } from 'k6/experimental/browser';
import { expect } from 'https://jslib.k6.io/k6-testing/0.5.0/index.js';

export const options = {
  scenarios: {
    ui: {
      executor: 'shared-iterations',
      options: {
        browser: {
          type: 'chromium',
        },
      },
    },
  }
};

// Create expect instance configured for browser testing with longer timeouts
const browserExpect = expect.configure({
  timeout: 15000, // Longer timeout for browser operations
  interval: 500, // Less frequent polling
});

export default async function () {
  const page = browser.newPage();
  await page.goto('https://test.k6.io');

  // Will wait up to 15 seconds for element to be visible
  await browserExpect(page.locator('h1')).toBeVisible();
}

CI/CD Configuration

JavaScript 
import { expect } from 'https://jslib.k6.io/k6-testing/0.5.0/index.js';

// Create expect instance configured for CI environment
const ciExpect = expect.configure({
  colorize: false, // Disable colors in CI logs
  display: 'inline', // inline output for CI
  timeout: 30000, // Longer timeout for CI environment
});

Development vs Production

JavaScript 
import { expect } from 'https://jslib.k6.io/k6-testing/0.5.0/index.js';

// Different configuration based on environment
const isDevelopment = __ENV.NODE_ENV === 'development';

const envExpect = expect.configure({
  timeout: isDevelopment ? 5000 : 15000,
  colorize: isDevelopment,
  display: isDevelopment ? 'pretty' : 'inline',
  softMode: isDevelopment ? 'continue' : 'fail',
});

Multiple Configured Instances

JavaScript 
import { expect } from 'https://jslib.k6.io/k6-testing/0.5.0/index.js';

export default function () {
  // Create specific expect instances for different scenarios
  const fastExpect = expect.configure({
    timeout: 1000,
    interval: 50,
  });

  const slowExpect = expect.configure({
    timeout: 30000,
    softMode: 'continue',
  });

  // Use appropriate instance for each test
  fastExpect(quickOperation()).toBe(true);
  slowExpect(slowOperation()).toBe(true);

  // Original expect instance still available
  expect(normalOperation()).toBe(true);
}

Soft Assertion Examples

JavaScript 
import http from 'k6/http';
import { expect } from 'https://jslib.k6.io/k6-testing/0.5.0/index.js';

// Create expect instance with soft assertions enabled
const softExpect = expect.configure({
  softMode: 'continue',
});

export default function () {
  const response = http.get('https://test-api.k6.io/public/crocodiles/1/');

  // These assertions will not stop test execution on failure
  softExpect(response.status).toBe(200);
  softExpect(response.json()).toHaveProperty('name');
  softExpect(response.json()).toHaveProperty('age');

  // Test continues even if assertions fail
  console.log('Test completed');
}