pest/tests/Features/Warnings.php

<?php

test('warning', function () {
    $this->fooqwdfwqdfqw;

    expect(true)->toBeTrue();
});

test('user warning', function () {
    trigger_error('This is a warning description', E_USER_WARNING);

    expect(true)->toBeTrue();
});

describe('a "describe" group of tests', function () {
    test('user warning', function () {
        trigger_error('This is a warning description', E_USER_WARNING);

        expect(true)->toBeTrue();
    });
});