Add automatic tests for confirmation modal config

Nice work thanks @sabina.h

Couple of minor issues to correct here:

/**
   * @var array
   */
  public static $modules = [
    'node',
    'user',
    'autologout',
  ];

You can use

 /**
   * {@inheritdoc}
   */ 

for this variable.

/**
   * Performs any pre-requisite tasks that need to happen.
   */
  protected function setUp() {

Here as well.

/**
   * Test that configurable text is displayed in the popup.
   */
  public function testConfigurableText() {

/**
   * Test that disable buttons settings option works as expected.
   */

Method summary should be in 3rd person. https://www.drupal.org/docs/develop/standards/api-documentation-and-comm...
Tests that configurable text is displayed in the popup.

$this->moduleConfig->set('timeout', 10)
      ->set('padding', 10)
      ->save();

sleep(15);

The timeout and sleep values could be lowered.

drupal_flush_all_caches();
$this->drupalGet('node');

If autologout settings are not updated because of caching then this is a problem that needs to be further investigated and find a fix.

Hi, I tested the provided patch and it applies and also tests go through on my local machine. If I understood @bcizej correctly, he also suggested to remove the drupal_flush_all_caches(); all other suggestions are added to the patch. I tested it without that line and the tests are still working. So marking this as Needs work, for that line to be removed, everything else looks good to me.
When uploading the interdiff file either choose the do not test option or upload with the .txt extension, so the file does not get tested :).

Tests are failing because of #3190324: Settings are not updated on cached pages

So we have to wait for that issue to get merged before testing again.

Meanwhile I cleaned the code a bit.

Removed unneeded node module in test and since this is a Functional Javascript test we can use

$this->assertSession()->waitForElement();

instead of

sleep()

Also we don't need to assert if user is logged in so I removed those assertions.
$this->drupalLogin() already asserts that though.

#3190324: Settings are not updated on cached pages has been commited so this is ready for review.

Tested the patch on the newest dev version of the module (which has the cache correction) locally on Drupal core 8.9.11 and test are also passing. The added changes did not break anything, so everything seems fine from my side. Marking this as RTBC.

Added to 1.4 release issue #3293639: Issues for 8.x-1.4 release