grafana/k6 · error

missing required argument 'testId'

Error message

missing required argument 'testId'

What it means

Thrown by locator.getByTestId() in the k6 browser module (internal/js/modules/k6/browser/browser/locator_mapping.go:272). The testID argument (string or RegExp, matched against the data-testid attribute unless testIdAttribute is reconfigured) is mandatory; the nullish guard rejects nil/undefined/null before parseStringOrRegex runs, because the internal ID selector cannot be constructed without it.

Solutions

1. Pass a string or RegExp: page.locator('form').getByTestId('submit-button')
2. Default the value first: const id = row.testId ?? 'submit-button'
3. If your app uses a different attribute, set it via the browser context options (testIdAttribute) rather than omitting the argument
4. Verify the fixture field name spelling matches what the script destructures

Example fix

// before
const btn = page.locator('form').getByTestId(row.testID); // fixture uses 'testId'

// after
const btn = page.locator('form').getByTestId(row.testId ?? 'submit-button');

const id = row.testId ?? 'submit-button';
if (id === undefined || id === null) throw new Error('testId is required');
const loc = parent.getByTestId(id);

function isNonEmptyStringOrRegExp(v) {
  return (typeof v === 'string' && v.length > 0) || v instanceof RegExp;
}
// usage: if (!isNonEmptyStringOrRegExp(id)) throw new Error('testId must be a non-empty string or RegExp');

try {
  const loc = parent.getByTestId(id);
} catch (e) {
  if (/missing required argument 'testId'/.test(e.message)) throw new Error(`testId missing for row ${i}`);
  throw e;
}

When it happens

Trigger: Calling parent.getByTestId() with no arguments; passing an explicitly null/undefined value; passing testID from an object property that does not exist (obj['data-test'] vs obj.testId).

Common situations: Test IDs sourced from JSON fixtures or spreadsheets with missing cells; teams migrating selectors from data-test to data-testid naming; destructuring that misnames the field; copy-paste of a getByTestId call with the argument left off.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• missing required argument 'placeholder'
• missing required argument 'role'
• missing required argument 'testId'
• missing required argument 'text'
• missing required argument 'title'

AI-assisted analysis of grafana/k6@8d06114777 (2026-08-18). Data as JSON: /api/errors/63be220ee06574d5. Report an issue: GitHub.

Appendix: source

Thrown at internal/js/modules/k6/browser/browser/locator_mapping.go:273

				return nil, errors.New("missing required argument 'placeholder'")
			}
			pplaceholder, popts := parseGetByBaseOptions(vu.Context(), placeholder, false, opts)

			ml := mapLocator(vu, lo.GetByPlaceholder(pplaceholder, popts))
			return rt.ToValue(ml).ToObject(rt), nil
		},
		"getByRole": func(role sobek.Value, opts sobek.Value) (*sobek.Object, error) {
			if k6common.IsNullish(role) {
				return nil, errors.New("missing required argument 'role'")
			}
			popts := parseGetByRoleOptions(vu.Context(), opts)

			ml := mapLocator(vu, lo.GetByRole(role.String(), popts))
			return rt.ToValue(ml).ToObject(rt), nil
		},
		"getByTestId": func(testID sobek.Value) (*sobek.Object, error) {
			if k6common.IsNullish(testID) {
				return nil, errors.New("missing required argument 'testId'")
			}
			ptestID := parseStringOrRegex(testID, false)

			ml := mapLocator(vu, lo.GetByTestID(ptestID))
			return rt.ToValue(ml).ToObject(rt), nil
		},
		"getByText": func(text sobek.Value, opts sobek.Value) (*sobek.Object, error) {
			if k6common.IsNullish(text) {
				return nil, errors.New("missing required argument 'text'")
			}
			ptext, popts := parseGetByBaseOptions(vu.Context(), text, true, opts)

			ml := mapLocator(vu, lo.GetByText(ptext, popts))
			return rt.ToValue(ml).ToObject(rt), nil
		},
		"getByTitle": func(title sobek.Value, opts sobek.Value) (*sobek.Object, error) {
			if k6common.IsNullish(title) {
				return nil, errors.New("missing required argument 'title'")

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