Bug: The example of "The Test Class“ is not working in Documets

[isiungk]

Direction
The example of "The Test Class“ is not working in Documets>Testing>Database>The Test Class.

Describe the bug
Following the CI4 documents, I created a test class as below:

<?php namespace App;

use CodeIgniter\Test\FeatureTestCase;

class MyAppTest extends FeatureTestCase
{
    public function setUp()
    {
        parent::setUp();
    }

    public function tearDown()
    {
        parent::tearDown();
    }
}

After run:

./phpunit ./tests/app/MyAppTest.php

I got:

PHP Fatal error:  Declaration of App\MyAppTest::setUp() must be compatible with CodeIgniter\Test\CIDatabaseTestCase::setUp(): void in ***/tests/app/MyAppTest.php on line 7

Afte learning the test demo in tests/unit/HealthTest.php, I modified the test class as below:

<?php namespace App;

use CodeIgniter\Test\FeatureTestCase;

class MyAppTest extends FeatureTestCase
{
    public function setUp(): void
    {
        parent::setUp();
    }

    public function tearDown(): void
    {
        parent::tearDown();
    }
}

and run './phpunit ./tests/app/MyAppTest.php' again, all comes OK.

I'm not sure if it's a bug, or the document is not up-to-date.

Rgds!

CodeIgniter 4 version
Which version (and branch, if applicable) the bug is in.
v4.0.3

Affected module(s)
Which package or class is the bug in, if known.
Maybe the documents, of "CodeIgniter\Test\FeatureTestCase" ? I'm not sure.

Expected behavior, and steps to reproduce if appropriate
None.

Context

• OS: macOS Catalina
• Web server: Apache/2.4.43 (Unix)
• PHP version: PHP/7.4.5

[samsonasik]

the doc need to be updated. Please provide PR