Console Logs And JavaScript Errors

Use browser.logs to capture what the page writes to the console and what JavaScript errors the browser reports. This is useful for failing tests on unexpected client-side errors, debugging flaky flows, or asserting that an app emitted a known log message.

Requires the default browser event connection. Console and JavaScript error capture requires enableBiDi: true (the default) and a browser that supports WebDriver BiDi. If you launch with enableBiDi: false, these methods throw a clear requires BiDi error.

Capture Timing

Capture is automatic. CraftDriver subscribes to log events at launch, so messages emitted at any point — including during the first navigation, before you ever touch browser.logs — are captured. There is nothing to enable and no listener to pre-arm:

await browser.navigateTo('https://example.com');
await browser.getByRole('button', { name: 'Show warning' }).click();
const messages = browser.logs.getMessages(); // includes the warning

The subscription rides the connect-time batch, so it costs no extra round trip and no measurable overhead. Use clearLogs() if you want to assert only on messages emitted after a certain point.

Read Collected Messages

const messages = browser.logs.getMessages();

for (const msg of messages) {
  console.log(`[${msg.level}] ${msg.text}`);
}

Each console message has:

Property	Description
type	Always 'console'
level	'debug', 'info', 'warn', or 'error'
text	Message text
method	Console method, such as 'log', 'warn', or 'error'
args	Arguments passed to console.*
timestamp	When the message was logged
stackTrace	Optional stack frames

Filter by level:

const warnings = browser.logs.getLogsByLevel('warn');
const errors = browser.logs.getLogsByLevel('error');

Read JavaScript Errors

const errors = browser.logs.getErrors();

for (const error of errors) {
  console.log(`Error: ${error.text}`);
}

Each JavaScript error has:

Property	Description
type	Always 'javascript'
level	Always 'error'
text	Error message
timestamp	When the error occurred
stackTrace	Optional stack frames with function, URL, line, and column

Wait For A Log Or Error

const consoleMessage = browser.logs.waitForConsole((msg) => {
  return msg.level === 'info' && msg.text.includes('Saved');
});

await browser.getByRole('button', { name: 'Save' }).click();
expect((await consoleMessage).text).toContain('Saved');

const pageError = browser.logs.waitForError((error) => {
  return error.text.includes('Cannot read properties');
});

await browser.getByRole('button', { name: 'Trigger error' }).click();
expect((await pageError).text).toContain('Cannot read properties');

Subscribe In Real Time

const unsubscribeConsole = browser.logs.onConsole((msg) => {
  if (msg.level === 'error') {
    console.log('Console error:', msg.text);
  }
});

const unsubscribeErrors = browser.logs.onError((error) => {
  console.log('JavaScript error:', error.text);
});

// Later:
unsubscribeConsole();
unsubscribeErrors();

Fail On Unexpected Errors

await browser.navigateTo('https://example.com');
await browser.getByRole('button', { name: 'Run flow' }).click();

browser.logs.assertNoErrors();

You can also inspect errors yourself:

const errors = browser.logs.getErrors();
expect(errors).toHaveLength(0);

Other Helpers

Method	Description
onLog(handler)	Subscribe to all log messages
on(level, handler)	Subscribe to one level: debug, info, warn, or error
getLogs()	Return all captured console and JavaScript error messages
clearLogs()	Clear all collected console messages and errors
waitForConsole(predicate, timeout?)	Wait for a matching console message
waitForError(predicate?, timeout?)	Wait for a JavaScript error
assertNoErrors()	Throw if any JavaScript errors were captured