diff --git a/connectors/class-connector-comments.php b/connectors/class-connector-comments.php
index 81c4dd0af..ac3274b3a 100644
--- a/connectors/class-connector-comments.php
+++ b/connectors/class-connector-comments.php
@@ -615,6 +615,10 @@ public function callback_comment_duplicate_trigger( $comment_data ) {
 		global $wpdb;
 		unset( $comment_data );
 
+		if ( ! empty( $wpdb->last_result ) ) {
+			return;
+		}
+
 		$comment_id = $wpdb->last_result[0]->comment_ID;
 		$comment    = get_comment( $comment_id );
 
diff --git a/tests/tests/connectors/test-class-connector-comments.php b/tests/tests/connectors/test-class-connector-comments.php
new file mode 100644
index 000000000..ec8dae33a
--- /dev/null
+++ b/tests/tests/connectors/test-class-connector-comments.php
@@ -0,0 +1,482 @@
+<?php
+namespace WP_Stream;
+
+class Test_WP_Stream_Connector_Comments extends WP_StreamTestCase {
+
+	public function setUp() {
+		parent::setUp();
+
+		// Make partial of Connector_ACF class, with mocked "log" function.
+		$this->mock = $this->getMockBuilder( Connector_Comments::class )
+			->setMethods( [ 'log' ] )
+			->getMock();
+
+		// Register connector.
+		$this->mock->register();
+	}
+
+	public function test_callback_wp_insert_comment() {
+		$post_id = wp_insert_post(
+			[
+				'post_title'    => 'Test post',
+				'post_content'  => 'Lorem ipsum dolor...',
+				'post_status'   => 'publish',
+			]
+		);
+
+		$this->mock->expects( $this->atLeastOnce() )
+			->method( 'log' )
+			->withConsecutive(
+				[
+					$this->equalTo(
+						_x(
+							'New %4$s by %1$s on %2$s %3$s',
+							'1: Comment author, 2: Post title 3: Comment status, 4: Comment type',
+							'stream'
+						)
+					),
+					$this->equalTo(
+						[
+							'user_name'      => 'Jim Bean',
+							'post_title'     => '"Test post"',
+							'comment_status' => 'pending approval',
+							'comment_type'   => 'comment',
+							'post_id'        => $post_id,
+							'is_spam'        => false,
+						]
+					),
+					$this->greaterThan( 0 ),
+					$this->equalTo( 'post' ),
+					$this->equalTo( 'created' ),
+					$this->equalTo( 0 )
+				],
+				[
+					$this->equalTo(
+						_x(
+							'Reply to %1$s\'s %5$s by %2$s on %3$s %4$s',
+							"1: Parent comment's author, 2: Comment author, 3: Post title, 4: Comment status, 5: Comment type",
+							'stream'
+						)
+					),
+					$this->equalTo(
+						[
+							'parent_user_name' => 'Jim Bean',
+							'user_name'        => 'Jim Bean',
+							'post_title'       => '"Test post"',
+							'comment_status'   => 'pending approval',
+							'comment_type'     => 'comment',
+							'post_id'          => "$post_id",
+						]
+					),
+					$this->greaterThan( 0 ),
+					$this->equalTo( 'post' ),
+					$this->equalTo( 'replied' ),
+					$this->equalTo( 0 )
+				]
+			);
+
+		// Do stuff.
+		$comment_id = wp_insert_comment(
+			[
+				'comment_content'      => 'Lorem ipsum dolor...',
+				'comment_author'       => 'Jim Bean',
+				'comment_author_email' => 'jim_bean@example.com',
+				'comment_author_IP'    => '::1',
+				'comment_post_ID'      => $post_id,
+			]
+		);
+		wp_insert_comment(
+			[
+				'comment_content'      => 'Lorem ipsum dolor...',
+				'comment_author'       => 'Jim Bean',
+				'comment_author_email' => 'jim_bean@example.com',
+				'comment_author_IP'    => '::1',
+				'comment_post_ID'      => $post_id,
+				'comment_parent'       => $comment_id,
+			]
+		);
+
+		$this->assertFalse( 0 === did_action( $this->action_prefix . 'callback_wp_insert_comment' ) );
+	}
+
+	public function test_callback_edit_comment() {
+		$post_id = wp_insert_post(
+			[
+				'post_title'    => 'Test post',
+				'post_content'  => 'Lorem ipsum dolor...',
+				'post_status'   => 'publish',
+			]
+		);
+		$comment_id = wp_insert_comment(
+			[
+				'comment_content'      => 'Lorem ipsum dolor...',
+				'comment_author'       => 'Jim Bean',
+				'comment_author_email' => 'jim_bean@example.com',
+				'comment_author_IP'    => '::1',
+				'comment_post_ID'      => $post_id,
+			]
+		);
+
+		$this->mock->expects( $this->atLeastOnce() )
+			->method( 'log' )
+			->with(
+				$this->equalTo(
+					_x(
+						'%1$s\'s %3$s on %2$s edited',
+						'1: Comment author, 2: Post title, 3: Comment type',
+						'stream'
+					)
+				),
+				$this->equalTo(
+					[
+						'user_name'    => 'Jim Bean',
+						'post_title'   => '"Test post"',
+						'comment_type' => 'comment',
+						'post_id'      => "$post_id",
+						'user_id'      => 0,
+					]
+				),
+				$this->equalTo( $comment_id ),
+				$this->equalTo( 'post' ),
+				$this->equalTo( 'edited' )
+			);
+
+		// Do stuff.
+		wp_update_comment(
+			[
+				'comment_ID'      => $comment_id,
+				'comment_content' => 'Lorem ipsum dolor... 2',
+			]
+		);
+
+		$this->assertFalse( 0 === did_action( $this->action_prefix . 'callback_edit_comment' ) );
+	}
+
+	public function test_callback_delete_comment() {
+		$post_id = wp_insert_post(
+			[
+				'post_title'    => 'Test post',
+				'post_content'  => 'Lorem ipsum dolor...',
+				'post_status'   => 'publish',
+			]
+		);
+		$comment_id = wp_insert_comment(
+			[
+				'comment_content'      => 'Lorem ipsum dolor...',
+				'comment_author'       => 'Jim Bean',
+				'comment_author_email' => 'jim_bean@example.com',
+				'comment_author_IP'    => '::1',
+				'comment_post_ID'      => $post_id,
+			]
+		);
+
+		$this->mock->expects( $this->atLeastOnce() )
+			->method( 'log' )
+			->with(
+				$this->equalTo(
+					_x(
+						'%1$s\'s %3$s on %2$s deleted permanently',
+						'1: Comment author, 2: Post title, 3: Comment type',
+						'stream'
+					)
+				),
+				$this->equalTo(
+					[
+						'user_name'    => 'Jim Bean',
+						'post_title'   => '"Test post"',
+						'comment_type' => 'comment',
+						'post_id'      => "$post_id",
+						'user_id'      => 0,
+					]
+				),
+				$this->equalTo( $comment_id ),
+				$this->equalTo( 'post' ),
+				$this->equalTo( 'deleted' )
+			);
+
+		// Do stuff.
+		wp_delete_comment( $comment_id, true );
+
+		$this->assertFalse( 0 === did_action( $this->action_prefix . 'callback_delete_comment' ) );
+	}
+
+	public function test_callback_trash_comment() {
+		$post_id = wp_insert_post(
+			[
+				'post_title'    => 'Test post',
+				'post_content'  => 'Lorem ipsum dolor...',
+				'post_status'   => 'publish',
+			]
+		);
+		$comment_id = wp_insert_comment(
+			[
+				'comment_content'      => 'Lorem ipsum dolor...',
+				'comment_author'       => 'Jim Bean',
+				'comment_author_email' => 'jim_bean@example.com',
+				'comment_author_IP'    => '::1',
+				'comment_post_ID'      => $post_id,
+			]
+		);
+
+		$this->mock->expects( $this->atLeastOnce() )
+			->method( 'log' )
+			->with(
+				$this->equalTo(
+					_x(
+						'%1$s\'s %3$s on %2$s trashed',
+						'1: Comment author, 2: Post title, 3: Comment type',
+						'stream'
+					)
+				),
+				$this->equalTo(
+					[
+						'user_name'    => 'Jim Bean',
+						'post_title'   => '"Test post"',
+						'comment_type' => 'comment',
+						'post_id'      => "$post_id",
+						'user_id'      => 0,
+					]
+				),
+				$this->equalTo( $comment_id ),
+				$this->equalTo( 'post' ),
+				$this->equalTo( 'trashed' )
+			);
+
+		// Do stuff.
+		wp_trash_comment( $comment_id );
+
+		$this->assertFalse( 0 === did_action( $this->action_prefix . 'callback_trash_comment' ) );
+	}
+
+	public function test_callback_untrash_comment() {
+		$post_id = wp_insert_post(
+			[
+				'post_title'    => 'Test post',
+				'post_content'  => 'Lorem ipsum dolor...',
+				'post_status'   => 'publish',
+			]
+		);
+		$comment_id = wp_insert_comment(
+			[
+				'comment_content'      => 'Lorem ipsum dolor...',
+				'comment_author'       => 'Jim Bean',
+				'comment_author_email' => 'jim_bean@example.com',
+				'comment_author_IP'    => '::1',
+				'comment_post_ID'      => $post_id,
+			]
+		);
+		wp_trash_comment( $comment_id );
+
+		$this->mock->expects( $this->atLeastOnce() )
+			->method( 'log' )
+			->with(
+				$this->equalTo(
+					_x(
+						'%1$s\'s %3$s on %2$s restored',
+						'1: Comment author, 2: Post title, 3: Comment type',
+						'stream'
+					)
+				),
+				$this->equalTo(
+					[
+						'user_name'    => 'Jim Bean',
+						'post_title'   => '"Test post"',
+						'comment_type' => 'comment',
+						'post_id'      => "$post_id",
+						'user_id'      => 0,
+					]
+				),
+				$this->equalTo( $comment_id ),
+				$this->equalTo( 'post' ),
+				$this->equalTo( 'untrashed' )
+			);
+
+		// Do stuff.
+		wp_untrash_comment( $comment_id );
+
+		$this->assertFalse( 0 === did_action( $this->action_prefix . 'callback_untrash_comment' ) );
+	}
+
+	public function test_callback_spam_comment() {
+		$post_id = wp_insert_post(
+			[
+				'post_title'    => 'Test post',
+				'post_content'  => 'Lorem ipsum dolor...',
+				'post_status'   => 'publish',
+			]
+		);
+		$comment_id = wp_insert_comment(
+			[
+				'comment_content'      => 'Lorem ipsum dolor...',
+				'comment_author'       => 'Jim Bean',
+				'comment_author_email' => 'jim_bean@example.com',
+				'comment_author_IP'    => '::1',
+				'comment_post_ID'      => $post_id,
+			]
+		);
+
+		$this->mock->expects( $this->atLeastOnce() )
+			->method( 'log' )
+			->with(
+				$this->equalTo(
+					_x(
+						'%1$s\'s %3$s on %2$s marked as spam',
+						'1: Comment author, 2: Post title, 3: Comment type',
+						'stream'
+					)
+				),
+				$this->equalTo(
+					[
+						'user_name'    => 'Jim Bean',
+						'post_title'   => '"Test post"',
+						'comment_type' => 'comment',
+						'post_id'      => "$post_id",
+						'user_id'      => 0,
+					]
+				),
+				$this->equalTo( $comment_id ),
+				$this->equalTo( 'post' ),
+				$this->equalTo( 'spammed' )
+			);
+
+		// Do stuff.
+		wp_spam_comment( $comment_id );
+
+		$this->assertFalse( 0 === did_action( $this->action_prefix . 'callback_spam_comment' ) );
+	}
+
+	public function test_callback_unspam_comment() {
+		$post_id = wp_insert_post(
+			[
+				'post_title'    => 'Test post',
+				'post_content'  => 'Lorem ipsum dolor...',
+				'post_status'   => 'publish',
+			]
+		);
+		$comment_id = wp_insert_comment(
+			[
+				'comment_content'      => 'Lorem ipsum dolor...',
+				'comment_author'       => 'Jim Bean',
+				'comment_author_email' => 'jim_bean@example.com',
+				'comment_author_IP'    => '::1',
+				'comment_post_ID'      => $post_id,
+			]
+		);
+		wp_spam_comment( $comment_id );
+
+		$this->mock->expects( $this->atLeastOnce() )
+			->method( 'log' )
+			->with(
+				$this->equalTo(
+					_x(
+						'%1$s\'s %3$s on %2$s unmarked as spam',
+						'1: Comment author, 2: Post title, 3: Comment type',
+						'stream'
+					)
+				),
+				$this->equalTo(
+					[
+						'user_name'    => 'Jim Bean',
+						'post_title'   => '"Test post"',
+						'comment_type' => 'comment',
+						'post_id'      => "$post_id",
+						'user_id'      => 0,
+					]
+				),
+				$this->equalTo( $comment_id ),
+				$this->equalTo( 'post' ),
+				$this->equalTo( 'unspammed' )
+			);
+
+		// Do stuff.
+		wp_unspam_comment( $comment_id );
+
+		$this->assertFalse( 0 === did_action( $this->action_prefix . 'callback_unspam_comment' ) );
+	}
+
+	public function test_callback_transition_comment_status() {
+		$post_id = wp_insert_post(
+			[
+				'post_title'    => 'Test post',
+				'post_content'  => 'Lorem ipsum dolor...',
+				'post_status'   => 'publish',
+			]
+		);
+		$comment_id = wp_insert_comment(
+			[
+				'comment_content'      => 'Lorem ipsum dolor...',
+				'comment_author'       => 'Jim Bean',
+				'comment_author_email' => 'jim_bean@example.com',
+				'comment_author_IP'    => '::1',
+				'comment_post_ID'      => $post_id,
+			]
+		);
+
+		$this->mock->expects( $this->atLeastOnce() )
+			->method( 'log' )
+			->with(
+				$this->equalTo(
+					_x(
+						'%1$s\'s %3$s %2$s',
+						'Comment status transition. 1: Comment author, 2: Post title, 3: Comment type',
+						'stream'
+					)
+				),
+				$this->equalTo(
+					[
+						'user_name'    => 'Jim Bean',
+						'new_status'   => 'unapproved',
+						'comment_type' => 'comment',
+						'old_status'   => 'pending approval',
+						'post_title'   => '"Test post"',
+						'post_id'      => "$post_id",
+						'user_id'      => 0,
+					]
+				),
+				$this->equalTo( $comment_id ),
+				$this->equalTo( 'post' ),
+				$this->equalTo( 'unapproved' )
+			);
+
+		// Do stuff.
+		wp_transition_comment_status( 'hold', 'pending approval', get_comment( $comment_id ) );
+
+		$this->assertFalse( 0 === did_action( $this->action_prefix . 'callback_transition_comment_status' ) );
+	}
+
+	public function test_callback_comment_duplicate_trigger() {
+		$post_id = wp_insert_post(
+			[
+				'post_title'    => 'Test post',
+				'post_content'  => 'Lorem ipsum dolor...',
+				'post_status'   => 'publish',
+			]
+		);
+		$comment_id = wp_insert_comment(
+			[
+				'comment_content'      => 'Lorem ipsum dolor...',
+				'comment_author'       => 'Jim Bean',
+				'comment_author_email' => 'jim_bean@example.com',
+				'comment_author_url'   => '',
+				'comment_author_IP'    => '::1',
+				'comment_post_ID'      => $post_id,
+			]
+		);
+
+		// Create duplicate comment and trigger mock.
+		wp_new_comment(
+			array(
+				'comment_content'      => 'Lorem ipsum dolor...',
+				'comment_author'       => 'Jim Bean',
+				'comment_author_email' => 'jim_bean@example.com',
+				'comment_author_url'   => '',
+				'comment_author_IP'    => '::1',
+				'comment_post_ID'      => $post_id,
+				'comment_type'         => 'post',
+			),
+			true
+		);
+
+		$this->assertFalse( 0 === did_action( $this->action_prefix . 'callback_comment_duplicate_trigger' ) );
+	}
+}