.../Comment/CommentHalJsonAnonTest.php             | 118 +++++++++++
 .../Comment/CommentHalJsonBasicAuthTest.php        |  30 +++
 .../EntityResource/Comment/CommentJsonAnonTest.php |  29 +++
 .../Comment/CommentJsonBasicAuthTest.php           |  46 +++++
 .../Comment/CommentResourceTestBase.php            | 224 +++++++++++++++++++++
 5 files changed, 447 insertions(+)

diff --git a/core/modules/hal/tests/src/Functional/EntityResource/Comment/CommentHalJsonAnonTest.php b/core/modules/hal/tests/src/Functional/EntityResource/Comment/CommentHalJsonAnonTest.php
new file mode 100644
index 0000000..1888ec7
--- /dev/null
+++ b/core/modules/hal/tests/src/Functional/EntityResource/Comment/CommentHalJsonAnonTest.php
@@ -0,0 +1,118 @@
+<?php
+
+namespace Drupal\Tests\hal\Functional\EntityResource\Comment;
+
+use Drupal\entity_test\Entity\EntityTest;
+use Drupal\Tests\hal\Functional\EntityResource\HalEntityNormalizationTrait;
+use Drupal\Tests\rest\Functional\AnonResourceTestTrait;
+use Drupal\Tests\rest\Functional\EntityResource\Comment\CommentResourceTestBase;
+use Drupal\user\Entity\User;
+
+/**
+ * @group hal
+ */
+class CommentHalJsonAnonTest extends CommentResourceTestBase  {
+
+  use HalEntityNormalizationTrait;
+  use AnonResourceTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['hal'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $format = 'hal_json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $mimeType = 'application/hal+json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $expectedErrorMimeType = 'application/json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getExpectedNormalizedEntity() {
+    $default_normalization = parent::getExpectedNormalizedEntity();
+
+    $normalization = $this->applyHalFieldNormalization($default_normalization);
+
+    $author = User::load(0);
+    $commented_entity = EntityTest::load(1);
+    return  $normalization + [
+      '_links' => [
+        'self' => [
+          'href' => $this->baseUrl . '/comment/1?_format=hal_json',
+        ],
+        'type' => [
+          'href' => $this->baseUrl . '/rest/type/comment/comment',
+        ],
+        $this->baseUrl . '/rest/relation/comment/comment/entity_id' => [
+          [
+            'href' => $this->baseUrl . '/entity_test/1?_format=hal_json',
+          ],
+        ],
+        $this->baseUrl . '/rest/relation/comment/comment/uid' => [
+          [
+            'href' => $this->baseUrl . '/user/0?_format=hal_json',
+            'lang' => 'en',
+          ],
+        ],
+      ],
+      '_embedded' => [
+        $this->baseUrl . '/rest/relation/comment/comment/entity_id' => [
+          [
+            '_links' => [
+              'self' => [
+                'href' => $this->baseUrl . '/entity_test/1?_format=hal_json',
+              ],
+              'type' => [
+                'href' => $this->baseUrl . '/rest/type/entity_test/bar',
+              ],
+            ],
+            'uuid' => [
+              ['value' => $commented_entity->uuid()]
+            ],
+          ],
+        ],
+        $this->baseUrl . '/rest/relation/comment/comment/uid' => [
+          [
+            '_links' => [
+              'self' => [
+                'href' => $this->baseUrl . '/user/0?_format=hal_json',
+              ],
+              'type' => [
+                'href' => $this->baseUrl . '/rest/type/user/user',
+              ],
+            ],
+            'uuid' => [
+              ['value' => $author->uuid()]
+            ],
+            'lang' => 'en',
+          ],
+        ],
+      ],
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getNormalizedEntityToCreate() {
+    return parent::getNormalizedEntityToCreate() + [
+      '_links' => [
+        'type' => [
+          'href' => $this->baseUrl . '/rest/type/comment/comment',
+        ],
+      ],
+    ];
+  }
+
+}
diff --git a/core/modules/hal/tests/src/Functional/EntityResource/Comment/CommentHalJsonBasicAuthTest.php b/core/modules/hal/tests/src/Functional/EntityResource/Comment/CommentHalJsonBasicAuthTest.php
new file mode 100644
index 0000000..9461f23
--- /dev/null
+++ b/core/modules/hal/tests/src/Functional/EntityResource/Comment/CommentHalJsonBasicAuthTest.php
@@ -0,0 +1,30 @@
+<?php
+
+namespace Drupal\Tests\hal\Functional\EntityResource\Comment;
+
+use Drupal\Tests\hal\Functional\HalJsonBasicAuthWorkaroundFor2805281Trait;
+use Drupal\Tests\rest\Functional\BasicAuthResourceTestTrait;
+
+/**
+ * @group hal
+ */
+class CommentHalJsonBasicAuthTest extends CommentHalJsonAnonTest {
+
+  use BasicAuthResourceTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['basic_auth'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $auth = 'basic_auth';
+
+  // @todo Fix in https://www.drupal.org/node/2805281: remove this trait usage.
+  use HalJsonBasicAuthWorkaroundFor2805281Trait {
+    HalJsonBasicAuthWorkaroundFor2805281Trait::verifyResponseWhenMissingAuthentication insteadof BasicAuthResourceTestTrait;
+  }
+
+}
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/Comment/CommentJsonAnonTest.php b/core/modules/rest/tests/src/Functional/EntityResource/Comment/CommentJsonAnonTest.php
new file mode 100644
index 0000000..47478aa
--- /dev/null
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Comment/CommentJsonAnonTest.php
@@ -0,0 +1,29 @@
+<?php
+
+namespace Drupal\Tests\rest\Functional\EntityResource\Comment;
+
+use Drupal\Tests\rest\Functional\AnonResourceTestTrait;
+
+/**
+ * @group rest
+ */
+class CommentJsonAnonTest extends CommentResourceTestBase {
+
+  use AnonResourceTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $format = 'json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $mimeType = 'application/json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $expectedErrorMimeType = 'application/json';
+
+}
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/Comment/CommentJsonBasicAuthTest.php b/core/modules/rest/tests/src/Functional/EntityResource/Comment/CommentJsonBasicAuthTest.php
new file mode 100644
index 0000000..470c158
--- /dev/null
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Comment/CommentJsonBasicAuthTest.php
@@ -0,0 +1,46 @@
+<?php
+
+namespace Drupal\Tests\rest\Functional\EntityResource\Comment;
+
+use Drupal\Tests\rest\Functional\BasicAuthResourceTestTrait;
+use Drupal\Tests\rest\Functional\JsonBasicAuthWorkaroundFor2805281Trait;
+use Psr\Http\Message\ResponseInterface;
+
+/**
+ * @group rest
+ */
+class CommentJsonBasicAuthTest extends CommentResourceTestBase {
+
+  use BasicAuthResourceTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['basic_auth'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $format = 'json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $mimeType = 'application/json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $expectedErrorMimeType = 'application/json';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $auth = 'basic_auth';
+
+  // @todo Fix in https://www.drupal.org/node/2805281: remove this trait usage.
+  use JsonBasicAuthWorkaroundFor2805281Trait {
+    JsonBasicAuthWorkaroundFor2805281Trait::verifyResponseWhenMissingAuthentication insteadof BasicAuthResourceTestTrait;
+  }
+
+}
diff --git a/core/modules/rest/tests/src/Functional/EntityResource/Comment/CommentResourceTestBase.php b/core/modules/rest/tests/src/Functional/EntityResource/Comment/CommentResourceTestBase.php
new file mode 100644
index 0000000..cb50160
--- /dev/null
+++ b/core/modules/rest/tests/src/Functional/EntityResource/Comment/CommentResourceTestBase.php
@@ -0,0 +1,224 @@
+<?php
+
+namespace Drupal\Tests\rest\Functional\EntityResource\Comment;
+
+use Drupal\comment\Entity\Comment;
+use Drupal\comment\Entity\CommentType;
+use Drupal\comment\Tests\CommentTestTrait;
+use Drupal\entity_test\Entity\EntityTest;
+use Drupal\Tests\rest\Functional\EntityResource\EntityResourceTestBase;
+use Drupal\user\Entity\User;
+
+abstract class CommentResourceTestBase extends EntityResourceTestBase {
+
+  use CommentTestTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['comment', 'entity_test'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $entityType = 'comment';
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUpAuthorization($method) {
+    switch ($method) {
+      case 'GET':
+        $this->grantPermissionsToTestedRole(['access comments', 'view test entity']);
+        break;
+      case 'POST':
+        $this->grantPermissionsToTestedRole(['post comments']);
+        break;
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function createEntity() {
+//    // Create a "Camelids" node type.
+//    NodeType::create([
+//      'name' => 'Camelids',
+//      'type' => 'camelids',
+//    ])->save();
+//
+//    // Create a "Llama" node.
+//    $node = Node::create(['type' => 'camelids']);
+//    $node->setTitle('Llama')
+//      ->setPublished(TRUE)
+//      ->setCreatedTime(123456789)
+//      ->setChangedTime(123456789)
+//      ->setRevisionCreationTime(123456789)
+//      ->save();
+
+    // Create a "bar" bundle for the "entity_test" entity type and create.
+    $bundle = 'bar';
+    entity_test_create_bundle($bundle, NULL, 'entity_test');
+
+    // Create a comment field on this bundle.
+    $this->addDefaultCommentField('entity_test', 'bar', 'comment');
+
+    // Create a "Camelids" test entity that the comment will be assigned to.
+    $commented_entity = EntityTest::create(array(
+      'name' => 'Camelids',
+      'type' => 'bar',
+    ));
+    $commented_entity->save();
+
+    // Create a "Llama" comment.
+    $comment = Comment::create([
+      'comment_body' => [
+        'value' => 'The name "llama" was adopted by European settlers from native Peruvians.',
+        'format' => 'plain_text',
+      ],
+      'entity_id' => $commented_entity->id(),
+      'entity_type' => 'entity_test',
+      'field_name' => 'comment',
+    ]);
+    $comment->setSubject('Llama')
+      ->setPublished(TRUE)
+      ->setCreatedTime(123456789)
+      ->setChangedTime(123456789);
+    $comment->save();
+
+    return $comment;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getExpectedNormalizedEntity() {
+    assert('$this->entity instanceof \Drupal\Core\Entity\EntityInterface', 'Entity must already have been created.');
+    $author = User::load(0);
+    return [
+      'cid' => [
+        ['value' => 1],
+      ],
+      'uuid' => [
+        ['value' => $this->entity->uuid()],
+      ],
+      'langcode' => [
+        [
+          'value' => 'en',
+        ],
+      ],
+      'comment_type' => [
+        [
+          'target_id' => 'comment',
+          'target_type' => 'comment_type',
+          'target_uuid' => CommentType::load('comment')->uuid(),
+        ],
+      ],
+      'subject' => [
+        [
+          'value' => 'Llama',
+        ],
+      ],
+      'status' => [
+        [
+          'value' => 1,
+        ],
+      ],
+      'created' => [
+        [
+          'value' => '123456789',
+        ],
+      ],
+      'changed' => [
+        [
+          'value' => '123456789',
+        ],
+      ],
+      'default_langcode' => [
+        [
+          'value' => TRUE,
+        ],
+      ],
+      'uid' => [
+        [
+          'target_id' => '0',
+          'target_type' => 'user',
+          'target_uuid' => $author->uuid(),
+          'url' => base_path() . 'user/0',
+        ],
+      ],
+      'pid' => [],
+      'entity_type' => [
+        [
+          'value' => 'entity_test',
+        ],
+      ],
+      'entity_id' => [
+        [
+          'target_id' => '1',
+          'target_type' => 'entity_test',
+          'target_uuid' => EntityTest::load(1)->uuid(),
+          'url' => base_path() . 'entity_test/1',
+        ],
+      ],
+      'field_name' => [
+        [
+          'value' => 'comment',
+        ],
+      ],
+      'name' => [],
+      'homepage' => [],
+      'thread' => [
+        [
+          'value' => '01/',
+        ],
+      ],
+      'comment_body' => [
+        [
+          'value' => 'The name "llama" was adopted by European settlers from native Peruvians.',
+          'format' => 'plain_text',
+        ],
+      ],
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getNormalizedEntityToCreate() {
+    return [
+      'comment_type' => [
+        [
+          'target_id' => 'comment',
+        ],
+      ],
+      'entity_type' => [
+        [
+          'value' => 'entity_test',
+        ],
+      ],
+      'entity_id' => [
+        [
+          'target_id' => EntityTest::load(1)->id(),
+        ],
+      ],
+      'field_name' => [
+        [
+          'value' => 'comment',
+        ],
+      ],
+      'subject' => [
+        [
+          'value' => 'Dramallama',
+        ],
+      ],
+      'comment_body' => [
+        [
+          'value' => 'Llamas are awesome.',
+          'format' => 'plain_text',
+        ],
+      ],
+    ];
+  }
+
+}