queryByAltText<E extends Element> method Null safety

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

Returns a single ImageElement, InputElement or AreaElement with the given text as the value of the alt attribute, defaulting to an exact match.

Returns null if no element is found. Use getByAltText if a RTE is expected.

Prefer using ByRole queries for ImageElements and ByLabelText queries for InputElements and AreaElements when possible in order to query for elements in a way that most reflects how the user would interact with them.

Related: queryAllByAltText

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

Example

The example below demonstrates the usage of the getByAltText query. However, the example is also relevant for getAllByAltText, queryByAltText, queryAllByAltText, findByAltText and findAllByAltText.

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

<img alt="Incredibles 2 Poster" src="/incredibles-2.png" />

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.img({'alt': 'Incredibles 2 Poster', 'src': '/incredibles-2.png'}),
    );

    expect(view.getByAltText(RegExp(r'incredibles.*? poster')), 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

text

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? queryByAltText<E extends Element>(
  /*TextMatch*/ dynamic text, {
  bool exact = true,
  NormalizerFn Function([NormalizerOptions?])? normalizer,
}) =>
    _jsQueryByAltText(
      getContainerForScope(),
      TextMatch.toJs(text),
      buildMatcherOptions(exact: exact, normalizer: normalizer),
    ) as E?;