Viewing github.com/facebook/react/packages/react-dom/src/__tests_

```
/**
```

 * Copyright (c) Meta Platforms, Inc. and affiliates.

```
 *
```

 * This source code is licensed under the MIT license found in the

 * LICENSE file in the root directory of this source tree.

```
 *
```
```
 * @emails react-core
```
```
 */
```
```
'use strict';
```
```
const React = require('react');
```
```
const ReactDOM = require('react-dom');
```

function expectWarnings(tags, warnings = [], withoutStack = 0) {

```
  tags = [...tags];
```
```
  warnings = [...warnings];
```
```
  let element = null;
```
```
  const containerTag = tags.shift();
```
```
  const container =
```
```
    containerTag === 'svg'
```

      ? document.createElementNS('http://www.w3.org/2000/svg', containerTag)

      : document.createElement(containerTag);

```
  while (tags.length) {
```
```
    const Tag = tags.pop();
```
```
    element = <Tag>{element}</Tag>;
```
```
  }
```
```
  if (warnings.length) {
```

    expect(() => ReactDOM.render(element, container)).toErrorDev(warnings, {

```
      withoutStack,
```
```
    });
```
```
  }
```
```
}
```
```
describe('validateDOMNesting', () => {
```
```
  it('allows valid nestings', () => {
```

    expectWarnings(['table', 'tbody', 'tr', 'td', 'b']);

```
    expectWarnings(
```
```
      ['body', 'datalist', 'option'],
```
```
      [
```

        gate(flags => !flags.enableHostSingletons)

          ? 'render(): Rendering components directly into document.body is discouraged'

```
          : null,
```
```
      ].filter(Boolean),
```
```
      1,
```
```
    );
```

    expectWarnings(['div', 'a', 'object', 'a']);

    expectWarnings(['div', 'p', 'button', 'p']);

    expectWarnings(['p', 'svg', 'foreignObject', 'p']);

    expectWarnings(['html', 'body', 'div']);

    // Invalid, but not changed by browser parsing so we allow them

    expectWarnings(['div', 'ul', 'ul', 'li']);

    expectWarnings(['div', 'label', 'div']);

    expectWarnings(['div', 'ul', 'li', 'section', 'li']);

    expectWarnings(['div', 'ul', 'li', 'dd', 'li']);

```
  });
```

  it('prevents problematic nestings', () => {

```
    expectWarnings(
```
```
      ['a', 'a'],
```
```
      [
```

        'validateDOMNesting(...): <a> cannot appear as a descendant of <a>.\n' +

```
          '    in a (at **)',
```
```
      ],
```
```
    );
```
```
    expectWarnings(
```
```
      ['form', 'form'],
```
```
      [
```

        'validateDOMNesting(...): <form> cannot appear as a descendant of <form>.\n' +

```
          '    in form (at **)',
```
```
      ],
```
```
    );
```
```
    expectWarnings(
```
```
      ['p', 'p'],
```
```
      [
```

        'validateDOMNesting(...): <p> cannot appear as a descendant of <p>.\n' +

```
          '    in p (at **)',
```
```
      ],
```
```
    );
```
```
    expectWarnings(
```
```
      ['table', 'tr'],
```
```
      [
```

        'validateDOMNesting(...): <tr> cannot appear as a child of <table>. ' +

          'Add a <tbody>, <thead> or <tfoot> to your code to match the DOM tree generated by the browser.\n' +

```
          '    in tr (at **)',
```
```
      ],
```
```
    );
```
```
    expectWarnings(
```

      ['div', 'ul', 'li', 'div', 'li'],

```
      [
```

        'validateDOMNesting(...): <li> cannot appear as a descendant of <li>.\n' +

```
          '    in li (at **)\n' +
```
```
          '    in div (at **)\n' +
```
```
          '    in li (at **)\n' +
```
```
          '    in ul (at **)',
```
```
      ],
```
```
    );
```
```
    expectWarnings(
```
```
      ['div', 'html'],
```
```
      [
```

        'validateDOMNesting(...): <html> cannot appear as a child of <div>.\n' +

```
          '    in html (at **)',
```
```
      ],
```
```
    );
```

    if (gate(flags => flags.enableHostSingletons)) {

```
      expectWarnings(
```
```
        ['body', 'body'],
```
```
        [
```

          'validateDOMNesting(...): <body> cannot appear as a child of <body>.\n' +

```
            '    in body (at **)',
```
```
        ],
```
```
      );
```
```
    } else {
```
```
      expectWarnings(
```
```
        ['body', 'body'],
```
```
        [
```

          'render(): Rendering components directly into document.body is discouraged',

          'validateDOMNesting(...): <body> cannot appear as a child of <body>.\n' +

```
            '    in body (at **)',
```
```
        ],
```
```
        1,
```
```
      );
```
```
    }
```

    if (gate(flags => flags.enableHostSingletons)) {

```
      expectWarnings(
```

        ['svg', 'foreignObject', 'body', 'p'],

```
        [
```

          'validateDOMNesting(...): <body> cannot appear as a child of <foreignObject>.\n' +

```
            '    in body (at **)\n' +
```

            '    in foreignObject (at **)',

          'Warning: You are mounting a new body component when a previous one has not first unmounted. It is an error to render more than one body component at a time and attributes and children of these components will likely fail in unpredictable ways. Please only render a single instance of <body> and if you need to mount a new one, ensure any previous ones have unmounted first.\n' +

```
            '    in body (at **)',
```
```
        ],
```
```
      );
```
```
    } else {
```
```
      expectWarnings(
```

        ['svg', 'foreignObject', 'body', 'p'],

```
        [
```

          'validateDOMNesting(...): <body> cannot appear as a child of <foreignObject>.\n' +

```
            '    in body (at **)\n' +
```

            '    in foreignObject (at **)',

```
        ],
```
```
      );
```
```
    }
```
```
  });
```
```
});
```