diff --git a/core/modules/simpletest/src/TestBase.php b/core/modules/simpletest/src/TestBase.php
index 021de93..dd583f5 100644
--- a/core/modules/simpletest/src/TestBase.php
+++ b/core/modules/simpletest/src/TestBase.php
@@ -1047,7 +1047,7 @@ private function prepareEnvironment() {
     // it will be associated with a different session-name. After the test-run
     // it can be safely destroyed.
     // @see TestBase::restoreEnvironment()
-    if (PHP_SAPI != 'cli' && session_status() == PHP_SESSION_ACTIVE) {
+    if (PHP_SAPI !== 'cli' && session_status() === PHP_SESSION_ACTIVE) {
       session_write_close();
     }
     $this->originalSessionName = session_name();
@@ -1168,7 +1168,7 @@ protected function tearDown() {
   private function restoreEnvironment() {
     // Destroy the session if one was started during the test-run.
     $_SESSION = array();
-    if (PHP_SAPI != 'cli' && session_status() == PHP_SESSION_ACTIVE) {
+    if (PHP_SAPI !== 'cli' && session_status() === PHP_SESSION_ACTIVE) {
       session_destroy();
       $params = session_get_cookie_params();
       setcookie(session_name(), '', REQUEST_TIME - 3600, $params['path'], $params['domain'], $params['secure'], $params['httponly']);
diff --git a/core/modules/simpletest/src/WebTestBase.php b/core/modules/simpletest/src/WebTestBase.php
index 4ddce53..cd4991d 100644
--- a/core/modules/simpletest/src/WebTestBase.php
+++ b/core/modules/simpletest/src/WebTestBase.php
@@ -786,7 +786,7 @@ protected function drupalLogout() {
   }
 
   /**
-   * Return the session name in use on the child site.
+   * Returns the session name in use on the child site.
    *
    * @return string
    *   The name of the session cookie.
@@ -826,8 +826,10 @@ protected function setUp() {
       'pass_raw' => $this->randomName(),
     ));
 
-    // The simpletest child site currently uses the same session name as the
-    // execution environment.
+    // Some tests (SessionTest and SessionHttpsTest) need to examine whether the
+    // proper session cookies were set on a response. Because the child site
+    // uses the same session name as the test runner, it is necessary to make
+    // that available to test-methods.
     // @todo: Introduce a setting such that the session name can be customized
     // for the child site.
     $this->session_name = $this->originalSessionName;
diff --git a/core/modules/system/src/Tests/Session/SessionTest.php b/core/modules/system/src/Tests/Session/SessionTest.php
index c64d1ad..47ef4b3 100644
--- a/core/modules/system/src/Tests/Session/SessionTest.php
+++ b/core/modules/system/src/Tests/Session/SessionTest.php
@@ -260,7 +260,7 @@ function testEmptySessionID() {
     // be valid. Closing the curl handler will stop the previous session ID
     // from persisting.
     $this->curlClose();
-    $this->additionalCurlOptions[CURLOPT_COOKIE] = rawurlencode($this->session_name) . '=;';
+    $this->additionalCurlOptions[CURLOPT_COOKIE] = rawurlencode($this->getSessionName()) . '=;';
     $this->drupalGet('session-test/id-from-cookie');
     $this->assertRaw("session_id:\n", 'Session ID is blank as sent from cookie header.');
     // Assert that we have an anonymous session now.