Session: Convert system functional tests to phpunit

This is super complex stuff.

1. +++ /dev/null
   @@ -1,47 +0,0 @@
   -    $actual_trace = $this->drupalGetAjax('session-test/trace-handler');
   
   +++ b/core/modules/system/tests/src/Functional/Session/StackSessionHandlerIntegrationTest.php
   @@ -0,0 +1,51 @@
   +    $options['query'][MainContentViewSubscriber::WRAPPER_FORMAT] = 'drupal_ajax';
   +    $headers[] = 'X-Requested-With: XMLHttpRequest';
   +    $actual_trace = json_decode($this->drupalGet('session-test/trace-handler', $options, $headers));
   

   WoW.

2. +++ b/core/modules/system/tests/src/Functional/Session/SessionTest.php
   @@ -322,4 +326,20 @@ public function assertSessionEmpty($empty) {
   +  protected function settingsSet($name, $value) {
   

   We have \Drupal\Core\Test\FunctionalTestSetupTrait::writeSettings for this.

Nitpicks ahead :)

1. +++ b/core/modules/system/tests/src/Functional/Session/SessionAuthenticationTest.php
   @@ -113,20 +114,24 @@ public function testBasicAuthNoSession() {
   +    // Mink stores some information in the session that breaks the next check if
   +    // not reset.
   +    $this->getSession()->restart();
   

   Do we know what that information is? Because adding that in sounds like a good improvement. If we don't this comment is good enough I think :)

2. +++ b/core/modules/system/tests/src/Functional/Session/SessionTest.php
   @@ -322,4 +326,20 @@ public function assertSessionEmpty($empty) {
   +   * Changes in memory settings.
   ...
   +   * @param $name
   +   *   The name of the setting to return.
   +   * @param $value
   +   *   The value of the setting.
   ...
   +  protected function settingsSet($name, $value) {
   +    $settings = Settings::getAll();
   +    $settings[$name] = $value;
   +    new Settings($settings);
   +  }
   

   This method name and description don't really fit together. We should probably either make the function name more narrow, or the description more broad. I think the second makes more sense.

   Also, there are no types for the parameters. We should add those (string, mixed - I think?)

3. +++ b/core/modules/system/tests/src/Functional/Session/StackSessionHandlerIntegrationTest.php
   @@ -0,0 +1,51 @@
   +  /**
   +   * Modules to enable.
   +   *
   +   * @var array
   +   */
   

   This can just be {@inheritdoc}

Some more nits.

1. +++ b/core/modules/system/tests/src/Functional/Session/SessionAuthenticationTest.php
   @@ -55,17 +55,18 @@ public function testSessionFromBasicAuthenticationDoesNotLeak() {
   +    $this->assertEqual($this->user->id(), json_decode($this->getSession()->getPage()->getContent())->user, 'The correct user is authenticated on a route with basic authentication.');
   ...
   +    $this->assertFalse(json_decode($this->getSession()->getPage()->getContent())->user, 'The user is no longer authenticated after visiting a page without basic authentication.');
   

   $this->getSession() can be a local var.

2. +++ b/core/modules/system/tests/src/Functional/Session/SessionTest.php
   @@ -96,9 +100,16 @@ public function testDataPersistence() {
   +    $session_cookie_value = $this->getSession()->getCookie($session_cookie_name);
   +    $this->getSession()->restart();
   ...
   +    $this->getSession()->setCookie($session_cookie_name, $session_cookie_value);
   

   Same as above.

Thanks, this looks good now.

Committed 6d3fbe9 and pushed to 8.7.x. Thanks!
Committed 472574a and pushed to 8.6.x. Thanks!

diff --git a/core/modules/system/tests/src/Functional/Session/SessionTest.php b/core/modules/system/tests/src/Functional/Session/SessionTest.php
index d84c71e425..0cee31f68c 100644
--- a/core/modules/system/tests/src/Functional/Session/SessionTest.php
+++ b/core/modules/system/tests/src/Functional/Session/SessionTest.php
@@ -2,7 +2,6 @@
 
 namespace Drupal\Tests\system\Functional\Session;
 
-use Drupal\Core\Site\Settings;
 use Drupal\Tests\BrowserTestBase;
 
 /**

Fixed unused on commit.