getByTestId<E extends Element> method Null safety

E getByTestId<E extends Element>(
  1. dynamic testId,
  2. {bool exact = true,
  3. NormalizerFn normalizer(
    1. [NormalizerOptions?]
    )?}
)
inherited

Returns a single element with the given testId value for the data-test-id attribute, defaulting to an exact match.

ByTestId Caveats

Guiding Principles / Priority In the spirit of the guiding principles, it is recommended to use this only when a more accessible query is not an option. Using data-test-id attributes do not resemble how your software is used and should be avoided if possible. That said, they are way better than querying based on DOM structure or styling css class names. Learn more about data-test-ids from the blog post "Making your UI tests resilient to change".

Enabling Test Mode When using a *ByTestId query on an OverReact component, you must call enableTestMode() within main() of your test(s).

Throws if no element is found. Use queryByTestId if a RTE is not expected.

Related: getAllByTestId

See: testing-library.com/docs/queries/bytestid/

Example

The example below demonstrates the usage of the getByTestId query. However, the example is also relevant for getAllByTestId, queryByTestId, queryAllByTestId, findByTestId and findAllByTestId.

Read more about the different types of queries to gain more clarity on which one suits your use-cases best.

<div data-test-id="custom-element" />

import 'package:react/react.dart' as react;
import 'package:react_testing_library/matchers.dart' show isInTheDocument;
import 'package:react_testing_library/react_testing_library.dart' as rtl;
import 'package:test/test.dart';

main() {
  test('', () {
    // Render the DOM shown in the example snippet above
    final view = rtl.render(
      react.div({'data-test-id': 'custom-element'}),
    );

    expect(view.getByTestId('custom-element'), isInTheDocument);
  });
}

NOTE: render() supports React vDom elements / custom components created using either the react or over_react packages.

The examples shown here use the react package since the react_testing_library does not have a direct dependency on over_react - but both libraries are fully supported.

Options

testId

This argument can be set to a String, RegExp, or a Function which returns true for a match and false for a mismatch.

See the JS TextMatch docs for more details and examples.

exact

Defaults to true; matches full strings, case-sensitive. When false, matches substrings and is not case-sensitive. It has no effect on regex or function arguments. In most cases using a regex instead of a string gives you more control over fuzzy matching and should be preferred over exact: false.

normalizer

An optional function which overrides normalization behavior.

Before running any matching logic against text in the DOM, DOM Testing Library automatically normalizes that text. By default, normalization consists of trimming whitespace from the start and end of text, and collapsing multiple adjacent whitespace characters into a single space.

If you want to prevent that normalization, or provide alternative normalization (e.g. to remove Unicode control characters), you can provide a normalizer function. This function will be given a string and is expected to return a normalized version of that string.

NOTE: Specifying a value for normalizer replaces the built-in normalization, but you can call getDefaultNormalizer to obtain a built-in normalizer, either to adjust that normalization or to call it from your own normalizer.

See the JS TextMatch precision and JS TextMatch normalization docs for more details and examples.

Implementation

E getByTestId<E extends Element>(
  /*TextMatch*/ dynamic testId, {
  bool exact = true,
  NormalizerFn Function([NormalizerOptions?])? normalizer,
}) {
  E jsQuery(dynamic testIdTextMatchValue) {
    return withErrorInterop(
      () => _jsGetByTestId(
        getContainerForScope(),
        testIdTextMatchValue,
        buildMatcherOptions(exact: exact, normalizer: normalizer),
      ) as E,
    );
  }

  if (testId is! String) return jsQuery(TextMatch.toJs(testId));

  // For strings, we need to jump through a few more hoops to ensure that we support matching a single
  // test id value on an element that may have more than one.
  try {
    return jsQuery(_convertTestIdStringToRegExp(testId, exact: exact));
  } catch (e, st) {
    if (e is TestingLibraryElementError) {
      // Replace regex produced by `_convertTestIdStringToRegExp` in the error message with the string provided
      // by the consumer since that is how they authored it.
      throw _errorWithMessageUsingStringTestIdProvided(
          errorThrownUsingRegExTestIdValue: e, stackTrace: st, testId: testId);
    } else {
      rethrow;
    }
  }
}