diff --git a/core/modules/system/src/Tests/Ajax/ElementValidationTest.php b/core/modules/system/src/Tests/Ajax/ElementValidationTest.php
index 81ed62de90cdfcd8524a04cb497f2f385baf6858..a6e9daa916f3f626fb4eb4470a718f63ea31ce3c 100644
--- a/core/modules/system/src/Tests/Ajax/ElementValidationTest.php
+++ b/core/modules/system/src/Tests/Ajax/ElementValidationTest.php
@@ -28,11 +28,10 @@ public static function getInfo() {
    * Ajax-enabled field fails due to the required field being empty.
    */
   function testAjaxElementValidation() {
-    $web_user = $this->drupalCreateUser();
     $edit = array('drivertext' => t('some dumb text'));
 
     // Post with 'drivertext' as the triggering element.
-    $post_result = $this->drupalPostAjaxForm('ajax_validation_test', $edit, 'drivertext');
+    $this->drupalPostAjaxForm('ajax_validation_test', $edit, 'drivertext');
     // Look for a validation failure in the resultant JSON.
     $this->assertNoText(t('Error message'), 'No error message in resultant JSON');
     $this->assertText('ajax_forms_test_validation_form_callback invoked', 'The correct callback was invoked');
@@ -41,7 +40,7 @@ function testAjaxElementValidation() {
     $edit = array('drivernumber' => 12345);
 
     // Post with 'drivernumber' as the triggering element.
-    $post_result = $this->drupalPostAjaxForm('ajax_validation_test', $edit, 'drivernumber');
+    $this->drupalPostAjaxForm('ajax_validation_test', $edit, 'drivernumber');
     // Look for a validation failure in the resultant JSON.
     $this->assertNoText(t('Error message'), 'No error message in resultant JSON');
     $this->assertText('ajax_forms_test_validation_number_form_callback invoked', 'The correct callback was invoked');
diff --git a/core/modules/system/src/Tests/Common/AddFeedTest.php b/core/modules/system/src/Tests/Common/AddFeedTest.php
index 2f4689bc26a5cec12305b97a15ba823726a02610..9997813db073c623d0a9306a8446a68b8b9bffd2 100644
--- a/core/modules/system/src/Tests/Common/AddFeedTest.php
+++ b/core/modules/system/src/Tests/Common/AddFeedTest.php
@@ -68,7 +68,7 @@ function testBasicFeedAddNoTitle() {
 
     $html_page = new HtmlPage();
 
-    foreach ($urls as $description => $feed_info) {
+    foreach ($urls as $feed_info) {
       $feed_link = new FeedLinkElement($feed_info['title'], $feed_info['url']);
       $html_page->addLinkElement($feed_link);
     }
diff --git a/core/modules/system/src/Tests/Common/WriteRecordTest.php b/core/modules/system/src/Tests/Common/WriteRecordTest.php
index fd6ac63ba9dd5516f1c6ff4dacce1ccc8f0ac574..f4ac5ff5249201026247a9fe3f0f7ce92106ab54 100644
--- a/core/modules/system/src/Tests/Common/WriteRecordTest.php
+++ b/core/modules/system/src/Tests/Common/WriteRecordTest.php
@@ -75,7 +75,7 @@ function testDrupalWriteRecord() {
     $person->name = 'Ringo';
     $person->age = NULL;
     $person->job = NULL;
-    $insert_result = drupal_write_record('test', $person);
+    drupal_write_record('test', $person);
     $this->assertTrue(isset($person->id), 'Primary key is set on record created with drupal_write_record().');
     $result = db_query("SELECT * FROM {test} WHERE id = :id", array(':id' => $person->id))->fetchObject();
     $this->assertIdentical($result->name, 'Ringo', 'Name field set.');
@@ -86,7 +86,7 @@ function testDrupalWriteRecord() {
     $person = new \stdClass();
     $person->name = 'Paul';
     $person->age = NULL;
-    $insert_result = drupal_write_record('test_null', $person);
+    drupal_write_record('test_null', $person);
     $this->assertTrue(isset($person->id), 'Primary key is set on record created with drupal_write_record().');
     $result = db_query("SELECT * FROM {test_null} WHERE id = :id", array(':id' => $person->id))->fetchObject();
     $this->assertIdentical($result->name, 'Paul', 'Name field set.');
@@ -95,7 +95,7 @@ function testDrupalWriteRecord() {
     // Insert a record - do not specify the value of a column that allows NULL.
     $person = new \stdClass();
     $person->name = 'Meredith';
-    $insert_result = drupal_write_record('test_null', $person);
+    drupal_write_record('test_null', $person);
     $this->assertTrue(isset($person->id), 'Primary key is set on record created with drupal_write_record().');
     $this->assertIdentical($person->age, 0, 'Age field set to default value.');
     $result = db_query("SELECT * FROM {test_null} WHERE id = :id", array(':id' => $person->id))->fetchObject();
@@ -105,7 +105,7 @@ function testDrupalWriteRecord() {
     // Update the newly created record.
     $person->name = 'Mary';
     $person->age = NULL;
-    $update_result = drupal_write_record('test_null', $person, array('id'));
+    drupal_write_record('test_null', $person, array('id'));
     $result = db_query("SELECT * FROM {test_null} WHERE id = :id", array(':id' => $person->id))->fetchObject();
     $this->assertIdentical($result->name, 'Mary', 'Name field set.');
     $this->assertIdentical($result->age, NULL, 'Age field set.');
@@ -113,20 +113,20 @@ function testDrupalWriteRecord() {
     // Insert a record - the "data" column should be serialized.
     $person = new \stdClass();
     $person->name = 'Dave';
-    $update_result = drupal_write_record('test_serialized', $person);
+    drupal_write_record('test_serialized', $person);
     $result = db_query("SELECT * FROM {test_serialized} WHERE id = :id", array(':id' => $person->id))->fetchObject();
     $this->assertIdentical($result->name, 'Dave', 'Name field set.');
     $this->assertIdentical($result->info, NULL, 'Info field set.');
 
     $person->info = array();
-    $update_result = drupal_write_record('test_serialized', $person, array('id'));
+    drupal_write_record('test_serialized', $person, array('id'));
     $result = db_query("SELECT * FROM {test_serialized} WHERE id = :id", array(':id' => $person->id))->fetchObject();
     $this->assertIdentical(unserialize($result->info), array(), 'Info field updated.');
 
     // Update the serialized record.
     $data = array('foo' => 'bar', 1 => 2, 'empty' => '', 'null' => NULL);
     $person->info = $data;
-    $update_result = drupal_write_record('test_serialized', $person, array('id'));
+    drupal_write_record('test_serialized', $person, array('id'));
     $result = db_query("SELECT * FROM {test_serialized} WHERE id = :id", array(':id' => $person->id))->fetchObject();
     $this->assertIdentical(unserialize($result->info), $data, 'Info field updated.');
 
diff --git a/core/modules/system/src/Tests/Database/DatabaseTestBase.php b/core/modules/system/src/Tests/Database/DatabaseTestBase.php
index 0aa4d5bdbae26fd02d6b8c0992f75c809995a23f..da14f5c4c98ee55a89179060097fd3b70856f2d5 100644
--- a/core/modules/system/src/Tests/Database/DatabaseTestBase.php
+++ b/core/modules/system/src/Tests/Database/DatabaseTestBase.php
@@ -76,7 +76,7 @@ static function addSampleData() {
       ))
       ->execute();
 
-    $ringo = db_insert('test')
+    db_insert('test')
       ->fields(array(
         'name' => 'Ringo',
         'age' => 28,
diff --git a/core/modules/system/src/Tests/Database/SelectOrderedTest.php b/core/modules/system/src/Tests/Database/SelectOrderedTest.php
index 62d4d2ab17ae2b06e5361e31f421ab37f3559fe8..9e20c8a014bbfdc456bd3421c85a14c0b587d599 100644
--- a/core/modules/system/src/Tests/Database/SelectOrderedTest.php
+++ b/core/modules/system/src/Tests/Database/SelectOrderedTest.php
@@ -25,7 +25,7 @@ public static function getInfo() {
    */
   function testSimpleSelectOrdered() {
     $query = db_select('test');
-    $name_field = $query->addField('test', 'name');
+    $query->addField('test', 'name');
     $age_field = $query->addField('test', 'age', 'age');
     $query->orderBy($age_field);
     $result = $query->execute();
@@ -46,7 +46,7 @@ function testSimpleSelectOrdered() {
    */
   function testSimpleSelectMultiOrdered() {
     $query = db_select('test');
-    $name_field = $query->addField('test', 'name');
+    $query->addField('test', 'name');
     $age_field = $query->addField('test', 'age', 'age');
     $job_field = $query->addField('test', 'job');
     $query->orderBy($job_field);
@@ -77,7 +77,7 @@ function testSimpleSelectMultiOrdered() {
    */
   function testSimpleSelectOrderedDesc() {
     $query = db_select('test');
-    $name_field = $query->addField('test', 'name');
+    $query->addField('test', 'name');
     $age_field = $query->addField('test', 'age', 'age');
     $query->orderBy($age_field, 'DESC');
     $result = $query->execute();
diff --git a/core/modules/system/src/Tests/Entity/EntityCacheTagsTestBase.php b/core/modules/system/src/Tests/Entity/EntityCacheTagsTestBase.php
index 8a2fbe7ac4ccb151752d2fa2d72dfbba236001c7..5d65632f933d575be59a78110ba34400c2f665a2 100644
--- a/core/modules/system/src/Tests/Entity/EntityCacheTagsTestBase.php
+++ b/core/modules/system/src/Tests/Entity/EntityCacheTagsTestBase.php
@@ -68,7 +68,6 @@ public function setUp() {
     if ($this->entity->getEntityType()->isFieldable()) {
       // Add field, so we can modify the Field and FieldInstance entities to
       // verify that changes to those indeed clear cache tags.
-      $field_name = drupal_strtolower($this->randomName());
       entity_create('field_config', array(
         'name' => 'configurable_field',
         'entity_type' => $this->entity->getEntityTypeId(),
diff --git a/core/modules/system/src/Tests/Form/ElementsTableSelectTest.php b/core/modules/system/src/Tests/Form/ElementsTableSelectTest.php
index 9ce3fb2fbae5f672185397a3f2b853557cb6a443..5bc8314b02814bca50091ac189bc64eb3606d861 100644
--- a/core/modules/system/src/Tests/Form/ElementsTableSelectTest.php
+++ b/core/modules/system/src/Tests/Form/ElementsTableSelectTest.php
@@ -166,11 +166,11 @@ function testMultipleTrueOptionchecker() {
     );
 
     // Test with a valid value.
-    list($processed_form, $form_state, $errors) = $this->formSubmitHelper($form, array('tableselect' => array('row1' => 'row1')));
+    list(, , $errors) = $this->formSubmitHelper($form, array('tableselect' => array('row1' => 'row1')));
     $this->assertFalse(isset($errors['tableselect']), 'Option checker allows valid values for checkboxes.');
 
     // Test with an invalid value.
-    list($processed_form, $form_state, $errors) = $this->formSubmitHelper($form, array('tableselect' => array('non_existing_value' => 'non_existing_value')));
+    list(, , $errors) = $this->formSubmitHelper($form, array('tableselect' => array('non_existing_value' => 'non_existing_value')));
     $this->assertTrue(isset($errors['tableselect']), 'Option checker disallows invalid values for checkboxes.');
 
   }
@@ -191,11 +191,11 @@ function testMultipleFalseOptionchecker() {
     );
 
     // Test with a valid value.
-    list($processed_form, $form_state, $errors) = $this->formSubmitHelper($form, array('tableselect' => 'row1'));
+    list(, , $errors) = $this->formSubmitHelper($form, array('tableselect' => 'row1'));
     $this->assertFalse(isset($errors['tableselect']), 'Option checker allows valid values for radio buttons.');
 
     // Test with an invalid value.
-    list($processed_form, $form_state, $errors) = $this->formSubmitHelper($form, array('tableselect' => 'non_existing_value'));
+    list(, , $errors) = $this->formSubmitHelper($form, array('tableselect' => 'non_existing_value'));
     $this->assertTrue(isset($errors['tableselect']), 'Option checker disallows invalid values for radio buttons.');
   }
 
diff --git a/core/modules/system/src/Tests/Lock/LockFunctionalTest.php b/core/modules/system/src/Tests/Lock/LockFunctionalTest.php
index d105c10ab151e2cfea4a2c6b7d4732e8b973e2b0..6b68385d599c8f7dba4b8fa4f2d1130338af27e3 100644
--- a/core/modules/system/src/Tests/Lock/LockFunctionalTest.php
+++ b/core/modules/system/src/Tests/Lock/LockFunctionalTest.php
@@ -61,7 +61,6 @@ public function testLockAcquire() {
 
     // Check the shut-down function.
     $lock_acquired_exit = 'TRUE: Lock successfully acquired in system_test_lock_exit()';
-    $lock_not_acquired_exit = 'FALSE: Lock not acquired in system_test_lock_exit()';
     $this->drupalGet('system-test/lock-exit');
     $this->assertText($lock_acquired_exit, 'Lock acquired by the other request before exit.', 'Lock');
     $this->assertTrue($lock->acquire('system_test_lock_exit'), 'Lock acquired by this request after the other request exits.', 'Lock');
diff --git a/core/modules/system/src/Tests/System/FrontPageTest.php b/core/modules/system/src/Tests/System/FrontPageTest.php
index 336c2cbd7e0668f0419a962d9d5586d682c48244..f017fafb228d133945191c9ad67939d58caaca76 100644
--- a/core/modules/system/src/Tests/System/FrontPageTest.php
+++ b/core/modules/system/src/Tests/System/FrontPageTest.php
@@ -52,7 +52,7 @@ public function testDrupalFrontPage() {
       'title' => $this->randomName(8),
       'promote' => 1,
     );
-    $node = $this->drupalCreateNode($settings);
+    $this->drupalCreateNode($settings);
     $this->drupalGet('');
     $this->assertTitle('Home | Drupal');
 
diff --git a/core/modules/system/tests/src/Controller/SystemControllerTest.php b/core/modules/system/tests/src/Controller/SystemControllerTest.php
index a1cdfaf888f21293852ab0e38dd6745981aac038..199a44f5cf9ced1b7ca7eeb55dfff01ffc28c9f8 100644
--- a/core/modules/system/tests/src/Controller/SystemControllerTest.php
+++ b/core/modules/system/tests/src/Controller/SystemControllerTest.php
@@ -125,8 +125,6 @@ public function providerTestSetLinkActiveClass() {
       'language' => 'nl',
       'query' => array(),
     );
-    // Nothing to do.
-    $markup = '<foo>bar</foo>';
     $situations[] = array('context' => $context, 'is active' => FALSE, 'attributes' => array());
     // Matching path, plus all matching variations.
     $attributes = array(
@@ -162,8 +160,6 @@ public function providerTestSetLinkActiveClass() {
       'language' => 'nl',
       'query' => array('foo' => 'bar'),
     );
-    // Nothing to do.
-    $markup = '<foo>bar</foo>';
     $situations[] = array('context' => $context, 'is active' => FALSE, 'attributes' => array());
     // Matching path, plus all matching variations.
     $attributes = array(
@@ -195,8 +191,6 @@ public function providerTestSetLinkActiveClass() {
       'language' => 'nl',
       'query' => array('foo' => 'bar'),
     );
-    // Nothing to do.
-    $markup = '<foo>bar</foo>';
     $situations[] = array('context' => $context, 'is active' => FALSE, 'attributes' => array());
     // Matching path, plus all matching variations.
     $attributes = array(
@@ -232,8 +226,6 @@ public function providerTestSetLinkActiveClass() {
       'language' => 'en',
       'query' => array('foo' => 'bar'),
     );
-    // Nothing to do.
-    $markup = '<foo>bar</foo>';
     $situations[] = array('context' => $context, 'is active' => FALSE, 'attributes' => array());
     // Matching path, plus all matching variations.
     $attributes = array(