PhpUnit deprecation notice: error guessing kernel directory

Question

This is my PhpUnit test class:

<?php

namespace tests\AppBundle\Controller;

use Symfony\Bundle\FrameworkBundle\Test\WebTestCase;

class SendEmailControllerTest extends WebTestCase
{
    public function testMailIsSentAndContentIsCorrect()
    {
        $client = static:: createClient();

        ...
    }
}

But when I try to run it, I get the error whose trace is:

Unable to guess the Kernel directory.
 C:\myProject\vendor\symfony\symfony\src\Symfony\Bundle\FrameworkBundle\Test\KernelTestCase.php:62
 C:\myProject\vendor\symfony\symfony\src\Symfony\Bundle\FrameworkBundle\Test\KernelTestCase.php:138
 C:\myProject\vendor\symfony\symfony\src\Symfony\Bundle\FrameworkBundle\Test\KernelTestCase.php:184
 C:\myProject\vendor\symfony\symfony\src\Symfony\Bundle\FrameworkBundle\Test\KernelTestCase.php:165
 C:\myProject\vendor\symfony\symfony\src\Symfony\Bundle\FrameworkBundle\Test\WebTestCase.php:33
 C:\myProject\tests\AppBundle\Controller\SendEmailControllerTest.php:12

ERRORS!
Tests: 1, Assertions: 0, Errors: 1.

Remaining deprecation notices (3)

  1x: Using the KERNEL_DIR environment variable or the automatic guessing based on the phpunit.xml / phpunit.xml.dist file location is deprecated since Symfony 3.4. Set the KERNEL_CLASS environment variable to the fully-qualified class name of your Kernel instead. Not setting the KERNEL_CLASS environment variable will throw an exception on 4.0 unless you override the :createKernel() or :getKernelClass() method.
    1x in SendEmailControllerTest::testMailIsSentAndContentIsCorrect from tests\AppBundle\Controller

  1x: The Symfony\Bundle\FrameworkBundle\Test\KernelTestCase::getPhpUnitXmlDir() method is deprecated since Symfony 3.4 and will be removed in 4.0.
    1x in SendEmailControllerTest::testMailIsSentAndContentIsCorrect from tests\AppBundle\Controller

  1x: The Symfony\Bundle\FrameworkBundle\Test\KernelTestCase::getPhpUnitCliConfigArgument() method is deprecated since Symfony 3.4 and will be removed in 4.0.
    1x in SendEmailControllerTest::testMailIsSentAndContentIsCorrect from tests\AppBundle\Controller
C:\xampp\php\php.exe C:/myProject/vendor/phpunit/phpunit/phpunit --no-configuration tests\AppBundle\Controller\SendEmailControllerTest C:\myProject\tests\AppBundle\Controller\SendEmailControllerTest.php --teamcity
Testing started at 23:09 ...
PHPUnit 5.6.0 by Sebastian Bergmann and contributors.


Process finished with exit code 2

But the problem is that I don't understand how to fix the deprecation issues indicated in the trace...

Edit:

Following the official documentation, I've added the in the phpunit.xml.dist

<?xml version="1.0" encoding="UTF-8"?>

<!-- https://phpunit.de/manual/current/en/appendixes.configuration.html -->
<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:noNamespaceSchemaLocation="http://schema.phpunit.de/4.8/phpunit.xsd"
         backupGlobals="false"
         colors="true"
         bootstrap="vendor/autoload.php"
>
    <php>
        <ini name="error_reporting" value="-1" />
        <env name="KERNEL_CLASS" value="App\Kernel" />
        <server name="KERNEL_CLASS" value="AppKernel" />
    </php>

    <testsuites>
        <testsuite name="Project Test Suite">
            <directory>tests</directory>
        </testsuite>
    </testsuites>

    <filter>
        <whitelist>
            <directory>src</directory>
            <exclude>
                <directory>src/*Bundle/Resources</directory>
                <directory>src/*/*Bundle/Resources</directory>
                <directory>src/*/Bundle/*Bundle/Resources</directory>
            </exclude>
        </whitelist>
    </filter>
</phpunit>

However:

1) I still get the same error

2) The code http://schema.phpunit.de/4.8/phpunit.xsd appears in red, with the message "URI is not registered (Settings | Languages & Frameworks | Schemas and DTDs). So I went to that place and in "External Schemas and DTDs" I added that URI, and the location being my project root. However, this red warning persists and I suspect it is related to the location, but where is it?

Answer 1

As documentation states

To run your functional tests, the WebTestCase class needs to know which is the application kernel to bootstrap it. The kernel class is usually defined in the KERNEL_CLASS environment variable (included in the default phpunit.xml.dist file provided by Symfony):

<?xml version="1.0" charset="utf-8" ?>
<phpunit>
    <php>
        <!-- the value is the FQCN of the application kernel -->
        <env name="KERNEL_CLASS" value="App\Kernel" />
    </php>
    <!-- ... -->
</phpunit>