diff --git a/tests/phpunit/tests/media/wpGenerateAttachmentMetadata.php b/tests/phpunit/tests/media/wpGenerateAttachmentMetadata.php
new file mode 100644
index 0000000000..82fe7dabd6
--- /dev/null
+++ b/tests/phpunit/tests/media/wpGenerateAttachmentMetadata.php
@@ -0,0 +1,89 @@
+<?php
+
+/**
+ * Tests for the `wp_generate_attachment_metadata()` function.
+ *
+ * @group media
+ * @covers ::wp_generate_attachment_metadata
+ */
+class Tests_Media_wpGenerateAttachmentMetadata extends WP_UnitTestCase {
+
+	public function tear_down() {
+		$this->remove_added_uploads();
+
+		parent::tear_down();
+	}
+
+	/**
+	 * Tests that filesize meta is generated for JPEGs.
+	 *
+	 * @ticket 49412
+	 *
+	 * @covers ::wp_create_image_subsizes
+	 */
+	public function test_wp_generate_attachment_metadata_includes_filesize_in_jpg_meta() {
+		$attachment = $this->factory->attachment->create_upload_object( DIR_TESTDATA . '/images/canola.jpg' );
+
+		$metadata = wp_get_attachment_metadata( $attachment );
+
+		$this->assertSame( wp_filesize( get_attached_file( $attachment ) ), $metadata['filesize'] );
+
+		foreach ( $metadata['sizes'] as $intermediate_size ) {
+			$this->assertArrayHasKey( 'filesize', $intermediate_size );
+			$this->assertNotEmpty( $intermediate_size['filesize'] );
+			$this->assertIsNumeric( $intermediate_size['filesize'] );
+		}
+	}
+
+	/**
+	 * Checks that filesize meta is generated for PNGs.
+	 *
+	 * @ticket 49412
+	 *
+	 * @covers ::wp_create_image_subsizes
+	 */
+	public function test_wp_generate_attachment_metadata_includes_filesize_in_png_meta() {
+		$attachment = $this->factory->attachment->create_upload_object( DIR_TESTDATA . '/images/test-image.png' );
+
+		$metadata = wp_get_attachment_metadata( $attachment );
+
+		$this->assertSame( wp_filesize( get_attached_file( $attachment ) ), $metadata['filesize'] );
+	}
+
+	/**
+	 * Checks that filesize meta is generated for PDFs.
+	 *
+	 * @ticket 49412
+	 */
+	public function test_wp_generate_attachment_metadata_includes_filesize_in_pdf_meta() {
+		$attachment = $this->factory->attachment->create_upload_object( DIR_TESTDATA . '/images/wordpress-gsoc-flyer.pdf' );
+
+		$metadata = wp_get_attachment_metadata( $attachment );
+
+		$this->assertSame( wp_filesize( get_attached_file( $attachment ) ), $metadata['filesize'] );
+	}
+
+	/**
+	 * Checks that filesize meta is generated for PSDs.
+	 *
+	 * @ticket 49412
+	 */
+	public function test_wp_generate_attachment_metadata_includes_filesize_in_psd_meta() {
+		if ( is_multisite() ) {
+			// PSD mime type is not allowed by default on multisite.
+			add_filter(
+				'upload_mimes',
+				static function( $mimes ) {
+					$mimes['psd'] = 'application/octet-stream';
+					return $mimes;
+				}
+			);
+		}
+
+		$attachment = $this->factory->attachment->create_upload_object( DIR_TESTDATA . '/images/test-image.psd' );
+
+		$metadata = wp_get_attachment_metadata( $attachment );
+
+		$this->assertSame( wp_filesize( get_attached_file( $attachment ) ), $metadata['filesize'] );
+	}
+}
diff --git a/tests/phpunit/tests/media/wpImageTagAddDecodingAttr.php b/tests/phpunit/tests/media/wpImageTagAddDecodingAttr.php
index 76fa203b7e..3ffe1bc6b4 100644
--- a/tests/phpunit/tests/media/wpImageTagAddDecodingAttr.php
+++ b/tests/phpunit/tests/media/wpImageTagAddDecodingAttr.php
@@ -1,7 +1,7 @@
 <?php
 
 /**
- * Tests the `wp_img_tag_add_decoding_attr()` function.
+ * Tests for the `wp_img_tag_add_decoding_attr()` function.
  *
  * @group media
  * @covers ::wp_img_tag_add_decoding_attr