diff --git a/includes/class-shortcodes.php b/includes/class-shortcodes.php
index 6ac73c03c..10018dd47 100644
--- a/includes/class-shortcodes.php
+++ b/includes/class-shortcodes.php
@@ -166,24 +166,26 @@ public static function content( $atts, $content, $tag ) {
 			if ( empty( $content ) ) {
 				$content = get_post_meta( $item->ID, '_wp_attachment_image_alt', true );
 			}
-		} else {
-			$content = \get_post_field( 'post_content', $item );
+		}
 
-			if ( 'yes' === $atts['apply_filters'] ) {
-				/** This filter is documented in wp-includes/post-template.php */
-				$content = \apply_filters( 'the_content', $content );
-			} else {
-				$content = do_blocks( $content );
-				$content = wptexturize( $content );
-				$content = wp_filter_content_tags( $content );
-			}
+		if ( empty( $content ) ) {
+			$content = \get_post_field( 'post_content', $item );
+		}
 
-			// Replace script and style elements.
-			$content = \preg_replace( '@<(script|style)[^>]*?>.*?</\\1>@si', '', $content );
-			$content = strip_shortcodes( $content );
-			$content = \trim( \preg_replace( '/[\n\r\t]/', '', $content ) );
+		if ( 'yes' === $atts['apply_filters'] ) {
+			/** This filter is documented in wp-includes/post-template.php */
+			$content = \apply_filters( 'the_content', $content );
+		} else {
+			$content = do_blocks( $content );
+			$content = wptexturize( $content );
+			$content = wp_filter_content_tags( $content );
 		}
 
+		// Replace script and style elements.
+		$content = \preg_replace( '@<(script|style)[^>]*?>.*?</\\1>@si', '', $content );
+		$content = strip_shortcodes( $content );
+		$content = \trim( \preg_replace( '/[\n\r\t]/', '', $content ) );
+
 		add_shortcode( 'ap_content', array( 'Activitypub\Shortcodes', 'content' ) );
 
 		return $content;
diff --git a/includes/transformer/class-attachment.php b/includes/transformer/class-attachment.php
index ef3e1d1fd..65f500ca8 100644
--- a/includes/transformer/class-attachment.php
+++ b/includes/transformer/class-attachment.php
@@ -24,11 +24,11 @@ class Attachment extends Post {
 	 * @return array The Attachments.
 	 */
 	protected function get_attachment() {
-		$mime_type  = get_post_mime_type( $this->item->ID );
-		$media_type = preg_replace( '/(\/[a-zA-Z]+)/i', '', $mime_type );
-		$type       = '';
+		$mime_type       = \get_post_mime_type( $this->item->ID );
+		$mime_type_parts = \explode( '/', $mime_type );
+		$type            = '';
 
-		switch ( $media_type ) {
+		switch ( $mime_type_parts[0] ) {
 			case 'audio':
 			case 'video':
 				$type = 'Document';
diff --git a/tests/includes/transformer/class-test-attachment.php b/tests/includes/transformer/class-test-attachment.php
new file mode 100644
index 000000000..6887da527
--- /dev/null
+++ b/tests/includes/transformer/class-test-attachment.php
@@ -0,0 +1,167 @@
+<?php
+/**
+ * Test file for Attachment transformer.
+ *
+ * @package ActivityPub
+ */
+
+namespace Activitypub\Tests\Transformer;
+
+use Activitypub\Transformer\Attachment;
+use WP_UnitTestCase;
+
+/**
+ * Test class for Attachment Transformer.
+ *
+ * @coversDefaultClass \Activitypub\Transformer\Attachment
+ */
+class Test_Attachment extends WP_UnitTestCase {
+	/**
+	 * Test attachment ID.
+	 *
+	 * @var int
+	 */
+	protected static $attachment_id;
+
+	/**
+	 * Create fake data before tests run.
+	 *
+	 * @param WP_UnitTest_Factory $factory Helper that creates fake data.
+	 */
+	public static function wpSetUpBeforeClass( $factory ) {
+		// Create test attachment
+		self::$attachment_id = $factory->attachment->create_object(
+			array(
+				'post_type'      => 'attachment',
+				'post_mime_type' => 'image/jpeg',
+				'post_title'     => 'Test Image',
+				'post_content'   => 'Test Image Description',
+			)
+		);
+	}
+
+	/**
+	 * Clean up after tests.
+	 */
+	public static function wpTearDownAfterClass() {
+		wp_delete_post( self::$attachment_id, true );
+	}
+
+	/**
+	 * Test get_type method.
+	 *
+	 * @covers ::get_type
+	 */
+	public function test_get_type() {
+		$attachment  = get_post( self::$attachment_id );
+		$transformer = new Attachment( $attachment );
+		$type        = $this->get_protected_method( $transformer, 'get_type' );
+
+		$this->assertEquals( 'Note', $type );
+	}
+
+	/**
+	 * Test get_attachment method with different mime types.
+	 *
+	 * @covers ::get_attachment
+	 * @dataProvider provide_mime_types
+	 */
+	public function test_get_attachment( $mime_type, $expected_type ) {
+		$attachment_id = self::factory()->attachment->create_object(
+			array(
+				'post_type'      => 'attachment',
+				'post_mime_type' => $mime_type,
+			)
+		);
+
+		$attachment  = get_post( $attachment_id );
+		$transformer = new Attachment( $attachment );
+		$result      = $this->get_protected_method( $transformer, 'get_attachment' );
+
+		$this->assertIsArray( $result );
+		$this->assertEquals( $expected_type, $result['type'] );
+		$this->assertEquals( $mime_type, $result['mediaType'] );
+		$this->assertArrayHasKey( 'url', $result );
+
+		wp_delete_post( $attachment_id, true );
+	}
+
+	/**
+	 * Test get_attachment method with alt text.
+	 *
+	 * @covers ::get_attachment
+	 */
+	public function test_get_attachment_with_alt() {
+		$alt_text = 'Test Alt Text';
+		update_post_meta( self::$attachment_id, '_wp_attachment_image_alt', $alt_text );
+
+		$attachment  = get_post( self::$attachment_id );
+		$transformer = new Attachment( $attachment );
+		$result      = $this->get_protected_method( $transformer, 'get_attachment' );
+
+		$this->assertArrayHasKey( 'name', $result );
+		$this->assertEquals( $alt_text, $result['name'] );
+	}
+
+	/**
+	 * Test to_object method.
+	 *
+	 * @covers ::to_object
+	 */
+	public function test_to_object() {
+		$attachment  = get_post( self::$attachment_id );
+		$transformer = new Attachment( $attachment );
+		$object      = $transformer->to_object();
+
+		$this->assertEquals( 'Note', $object->get_type() );
+		$this->assertEquals( home_url( '?p=' . self::$attachment_id ), $object->get_id() );
+		$this->assertNull( $object->get_name() );
+	}
+
+	/**
+	 * Data provider for mime types.
+	 *
+	 * @return array Test data.
+	 */
+	public function provide_mime_types() {
+		return array(
+			'image' => array(
+				'image/jpeg',
+				'Image',
+			),
+			'audio' => array(
+				'audio/mpeg',
+				'Document',
+			),
+			'video' => array(
+				'video/mp4',
+				'Document',
+			),
+			'pdf'   => array(
+				'application/pdf',
+				'',
+			),
+			'text'  => array(
+				'text/plain',
+				'',
+			),
+		);
+	}
+
+	/**
+	 * Helper method to access protected methods.
+	 *
+	 * @param object $object     Object instance.
+	 * @param string $method_name Method name.
+	 * @param array  $parameters Optional parameters.
+	 *
+	 * @return mixed Method result.
+	 */
+	protected function get_protected_method( $object, $method_name, $parameters = array() ) {
+		$reflection = new \ReflectionClass( get_class( $object ) );
+		$method     = $reflection->getMethod( $method_name );
+		$method->setAccessible( true );
+
+		return $method->invokeArgs( $object, $parameters );
+	}
+}