diff --git a/core/lib/Drupal/Core/Cache/Cache.php b/core/lib/Drupal/Core/Cache/Cache.php
index ba99651..23f4704 100644
--- a/core/lib/Drupal/Core/Cache/Cache.php
+++ b/core/lib/Drupal/Core/Cache/Cache.php
@@ -80,10 +80,10 @@ public static function mergeTags($a = array(), $b = array()) {
    */
   public static function mergeMaxAges($a = Cache::PERMANENT, $b = Cache::PERMANENT) {
     // If one of the values is Cache::PERMANENT, return the other value.
-    if ($a == Cache::PERMANENT){
+    if ($a === Cache::PERMANENT){
       return $b;
     }
-    if ($b == Cache::PERMANENT){
+    if ($b === Cache::PERMANENT){
       return $a;
     }
 
diff --git a/core/lib/Drupal/Core/Entity/EntityViewBuilder.php b/core/lib/Drupal/Core/Entity/EntityViewBuilder.php
index c20d9a6..086a826 100644
--- a/core/lib/Drupal/Core/Entity/EntityViewBuilder.php
+++ b/core/lib/Drupal/Core/Entity/EntityViewBuilder.php
@@ -371,7 +371,6 @@ public function resetCache(array $entities = NULL) {
         $tags = Cache::mergeTags($tags, $entity->getCacheTags());
         $tags = Cache::mergeTags($tags, $entity->getEntityType()->getListCacheTags());
       }
-      $tags = Cache::mergeTags($tags);
       Cache::invalidateTags($tags);
     }
     else {
diff --git a/core/modules/block/src/BlockViewBuilder.php b/core/modules/block/src/BlockViewBuilder.php
index 9fd3ba0..4266fd4 100644
--- a/core/modules/block/src/BlockViewBuilder.php
+++ b/core/modules/block/src/BlockViewBuilder.php
@@ -49,14 +49,13 @@ public function viewMultiple(array $entities = array(), $view_mode = 'full', $la
       $configuration = $plugin->getConfiguration();
 
       $cache_tags = Cache::mergeTags(
-        $this->getCacheTags(), // Block view builder cache tag.
-        $entity->getCacheTags() // Block entity cache tag.
+        $this->getCacheTags(),
+        $entity->getCacheTags()
       );
       $cache_tags = Cache::mergeTags(
         $cache_tags,
-        $plugin->getCacheTags() // Block plugin cache tags.
+        $plugin->getCacheTags()
       );
-      $cache_tags = Cache::mergeTags($cache_tags);
 
       // Create the render array for the block as a whole.
       // @see template_preprocess_block().
diff --git a/core/modules/block_content/src/Tests/BlockContentCacheTagsTest.php b/core/modules/block_content/src/Tests/BlockContentCacheTagsTest.php
index 1590640..c3a07c4 100644
--- a/core/modules/block_content/src/Tests/BlockContentCacheTagsTest.php
+++ b/core/modules/block_content/src/Tests/BlockContentCacheTagsTest.php
@@ -93,14 +93,12 @@ public function testBlock() {
     $expected_block_cache_contexts = ['languages:' . LanguageInterface::TYPE_INTERFACE, 'theme'];
     $expected_block_cache_tags = Cache::mergeTags(['block_view', 'rendered'], $block->getCacheTags());
     $expected_block_cache_tags = Cache::mergeTags($expected_block_cache_tags, $block->getPlugin()->getCacheTags());
-    $expected_block_cache_tags = Cache::mergeTags($expected_block_cache_tags);
 
     // Expected contexts and tags for the BlockContent entity.
     // @see \Drupal\Core\Entity\EntityViewBuilder::getBuildDefaults().
     $expected_entity_cache_contexts = ['theme'];
     $expected_entity_cache_tags = Cache::mergeTags(['block_content_view'], $this->entity->getCacheTags());
     $expected_entity_cache_tags = Cache::mergeTags($expected_entity_cache_tags, $this->getAdditionalCacheTagsForEntity($this->entity));
-    $expected_entity_cache_tags = Cache::mergeTags($expected_entity_cache_tags);
 
     // Verify that what was render cached matches the above expectations.
     $cid = $this->createCacheId($expected_block_cache_keys, $expected_block_cache_contexts);
diff --git a/core/modules/system/src/Tests/Entity/EntityCacheTagsTestBase.php b/core/modules/system/src/Tests/Entity/EntityCacheTagsTestBase.php
index edc4889..351447d 100644
--- a/core/modules/system/src/Tests/Entity/EntityCacheTagsTestBase.php
+++ b/core/modules/system/src/Tests/Entity/EntityCacheTagsTestBase.php
@@ -371,7 +371,6 @@ public function testReferencedEntity() {
       $referencing_entity_cache_tags,
       ['rendered']
     );
-    $referencing_entity_cache_tags = Cache::mergeTags($referencing_entity_cache_tags);
 
     $non_referencing_entity_cache_tags = Cache::mergeTags(
       $this->nonReferencingEntity->getCacheTags(),
@@ -381,7 +380,6 @@ public function testReferencedEntity() {
       $non_referencing_entity_cache_tags,
       ['rendered']
     );
-    $non_referencing_entity_cache_tags = Cache::mergeTags($non_referencing_entity_cache_tags);
 
     // Generate the cache tags for all two possible entity listing paths.
     // 1. list cache tag only (listing query has no match)
@@ -408,7 +406,6 @@ public function testReferencedEntity() {
     $this->verifyPageCache($referencing_entity_url, 'MISS');
 
     // Verify a cache hit, but also the presence of the correct cache tags.
-    $expectedTags = [];
     $expectedTags = Cache::mergeTags($referencing_entity_cache_tags, $page_cache_tags);
     $expectedTags = Cache::mergeTags($expectedTags, $page_cache_tags_referencing_entity);
     $this->verifyPageCache($referencing_entity_url, 'HIT', $expectedTags);
@@ -440,7 +437,6 @@ public function testReferencedEntity() {
     $this->verifyPageCache($listing_url, 'MISS');
 
     // Verify a cache hit, but also the presence of the correct cache tags.
-    $expectedTags = [];
     $expectedTags = Cache::mergeTags($referencing_entity_cache_tags, $page_cache_tags);
     $expectedTags = Cache::mergeTags($expectedTags, $page_cache_tags_referencing_entity);
     $this->verifyPageCache($listing_url, 'HIT', $expectedTags);
diff --git a/core/modules/tracker/src/Tests/TrackerTest.php b/core/modules/tracker/src/Tests/TrackerTest.php
index c20c054..5ff88e6 100644
--- a/core/modules/tracker/src/Tests/TrackerTest.php
+++ b/core/modules/tracker/src/Tests/TrackerTest.php
@@ -78,8 +78,11 @@ function testTrackerAll() {
 
     // Assert cache contexts, specifically the pager and node access contexts.
     $this->assertCacheContexts(['languages:language_interface', 'theme', 'url.query_args.pagers:0', 'user.node_grants:view', 'user.permissions']);
+
     // Assert cache tags for the visible node and node list cache tag.
-    $this->assertCacheTags(Cache::mergeTags($published->getCacheTags(), $published->getOwner()->getCacheTags(), ['node_list', 'rendered']));
+    $expected_tags = Cache::mergeTags($published->getCacheTags(), $published->getOwner()->getCacheTags());
+    $expected_tags = Cache::mergeTags($expected_tags, ['node_list', 'rendered']);
+    $this->assertCacheTags($expected_tags);
 
     // Delete a node and ensure it no longer appears on the tracker.
     $published->delete();
@@ -143,16 +146,15 @@ function testTrackerUser() {
     // Assert cache contexts; the node grant context is not directly visible due
     // to it being implied by the user context.
     $this->assertCacheContexts(['languages:language_interface', 'theme', 'url.query_args.pagers:0', 'user']);
+
     // Assert cache tags for the visible nodes (including owners) and node list
     // cache tag.
-    $tags = Cache::mergeTags(
-      $my_published->getCacheTags(),
-      $my_published->getOwner()->getCacheTags(),
-      $other_published_my_comment->getCacheTags(),
-      $other_published_my_comment->getOwner()->getCacheTags(),
-      ['node_list', 'rendered']
-    );
-    $this->assertCacheTags($tags);
+    $expected_tags = Cache::mergeTags($my_published->getCacheTags(), $my_published->getOwner()->getCacheTags());
+    $expected_tags = Cache::mergeTags($expected_tags, $other_published_my_comment->getCacheTags());
+    $expected_tags = Cache::mergeTags($expected_tags, $other_published_my_comment->getOwner()->getCacheTags());
+    $expected_tags = Cache::mergeTags($expected_tags, ['node_list', 'rendered']);
+
+    $this->assertCacheTags($expected_tags);
 
     $this->assertLink($my_published->label());
     $this->assertNoLink($unpublished->label());