diff --git a/opengraphkt/src/test/kotlin/fr/lengrand/opengraphkt/GeneratorTest.kt b/opengraphkt/src/test/kotlin/fr/lengrand/opengraphkt/GeneratorTest.kt
index c9a7b02..9382694 100644
--- a/opengraphkt/src/test/kotlin/fr/lengrand/opengraphkt/GeneratorTest.kt
+++ b/opengraphkt/src/test/kotlin/fr/lengrand/opengraphkt/GeneratorTest.kt
@@ -3,6 +3,7 @@ package fr.lengrand.opengraphkt
 import org.junit.jupiter.api.Test
 import java.net.URI
 import java.time.OffsetDateTime
+import kotlin.test.assertEquals
 import kotlin.test.assertTrue
 
 class GeneratorTest {
@@ -103,7 +104,7 @@ class GeneratorTest {
         assertTrue(html.contains("<meta property=\"og:image:width\" content=\"800\" />"))
         assertTrue(html.contains("<meta property=\"og:image:height\" content=\"600\" />"))
         assertTrue(html.contains("<meta property=\"og:image:alt\" content=\"Test Image 1\" />"))
-        
+
         assertTrue(html.contains("<meta property=\"og:image\" content=\"https://example.com/image2.png\" />"))
         assertTrue(html.contains("<meta property=\"og:image:type\" content=\"image/png\" />"))
         assertTrue(html.contains("<meta property=\"og:image:width\" content=\"1024\" />"))
@@ -248,7 +249,7 @@ class GeneratorTest {
         assertTrue(html.contains("<meta property=\"og:video:width\" content=\"1280\" />"))
         assertTrue(html.contains("<meta property=\"og:video:height\" content=\"720\" />"))
         assertTrue(html.contains("<meta property=\"og:video:duration\" content=\"120\" />"))
-        
+
         assertTrue(html.contains("<meta property=\"og:video:actor\" content=\"Actor 1\" />"))
         assertTrue(html.contains("<meta property=\"og:video:actor\" content=\"Actor 2\" />"))
         assertTrue(html.contains("<meta property=\"og:video:director\" content=\"Director\" />"))
@@ -292,6 +293,448 @@ class GeneratorTest {
         assertTrue(html.contains("<meta property=\"og:title\" content=\"Test &quot;Quoted&quot; Title\" />"))
     }
 
+    @Test
+    fun `test generate with audio`() {
+        // Create a Data object with audio metadata
+        val data = Data(
+            tags = emptyList(),
+            title = "Test Audio",
+            type = "website",
+            url = URI("https://example.com/audio").toURL(),
+            description = null,
+            siteName = null,
+            determiner = null,
+            locale = null,
+            localeAlternate = emptyList(),
+            images = emptyList(),
+            videos = emptyList(),
+            audios = listOf(
+                Audio(
+                    url = "https://example.com/audio.mp3",
+                    secureUrl = "https://secure.example.com/audio.mp3",
+                    type = "audio/mpeg"
+                ),
+                Audio(
+                    url = "https://example.com/audio.wav",
+                    secureUrl = null,
+                    type = "audio/wav"
+                )
+            ),
+            article = null,
+            profile = null,
+            book = null,
+            musicSong = null,
+            musicAlbum = null,
+            musicPlaylist = null,
+            musicRadioStation = null,
+            videoMovie = null,
+            videoEpisode = null
+        )
+
+        val html = generator.generate(data)
+
+        // Verify that all audio tags are generated correctly
+        assertTrue(html.contains("<meta property=\"og:audio\" content=\"https://example.com/audio.mp3\" />"))
+        assertTrue(html.contains("<meta property=\"og:audio:secure_url\" content=\"https://secure.example.com/audio.mp3\" />"))
+        assertTrue(html.contains("<meta property=\"og:audio:type\" content=\"audio/mpeg\" />"))
+
+        assertTrue(html.contains("<meta property=\"og:audio\" content=\"https://example.com/audio.wav\" />"))
+        assertTrue(html.contains("<meta property=\"og:audio:type\" content=\"audio/wav\" />"))
+    }
+
+    @Test
+    fun `test generate with book`() {
+        // Create a Data object with book metadata
+        val data = Data(
+            tags = emptyList(),
+            title = "Test Book",
+            type = "book",
+            url = URI("https://example.com/book").toURL(),
+            description = null,
+            siteName = null,
+            determiner = null,
+            locale = null,
+            localeAlternate = emptyList(),
+            images = emptyList(),
+            videos = emptyList(),
+            audios = emptyList(),
+            article = null,
+            profile = null,
+            book = Book(
+                authors = listOf("Author 1", "Author 2"),
+                isbn = "978-3-16-148410-0",
+                releaseDate = OffsetDateTime.parse("2023-01-01T00:00:00Z"),
+                tags = listOf("fiction", "fantasy")
+            ),
+            musicSong = null,
+            musicAlbum = null,
+            musicPlaylist = null,
+            musicRadioStation = null,
+            videoMovie = null,
+            videoEpisode = null
+        )
+
+        val html = generator.generate(data)
+
+        // Verify that all book tags are generated correctly
+        assertTrue(html.contains("<meta property=\"og:book:author\" content=\"Author 1\" />"))
+        assertTrue(html.contains("<meta property=\"og:book:author\" content=\"Author 2\" />"))
+        assertTrue(html.contains("<meta property=\"og:book:isbn\" content=\"978-3-16-148410-0\" />"))
+        assertTrue(html.contains("<meta property=\"og:book:release_date\" content=\"2023-01-01T00:00:00Z\" />"))
+        assertTrue(html.contains("<meta property=\"og:book:tag\" content=\"fiction\" />"))
+        assertTrue(html.contains("<meta property=\"og:book:tag\" content=\"fantasy\" />"))
+    }
+
+    @Test
+    fun `test generate with music song`() {
+        // Create a Data object with music.song metadata
+        val data = Data(
+            tags = emptyList(),
+            title = "Test Song",
+            type = "music.song",
+            url = URI("https://example.com/song").toURL(),
+            description = null,
+            siteName = null,
+            determiner = null,
+            locale = null,
+            localeAlternate = emptyList(),
+            images = emptyList(),
+            videos = emptyList(),
+            audios = emptyList(),
+            article = null,
+            profile = null,
+            book = null,
+            musicSong = MusicSong(
+                duration = 240,
+                album = "Test Album",
+                albumDisc = 1,
+                albumTrack = 5,
+                musician = listOf("Musician 1", "Musician 2")
+            ),
+            musicAlbum = null,
+            musicPlaylist = null,
+            musicRadioStation = null,
+            videoMovie = null,
+            videoEpisode = null
+        )
+
+        val html = generator.generate(data)
+
+        // Verify that all music.song tags are generated correctly
+        assertTrue(html.contains("<meta property=\"og:music:duration\" content=\"240\" />"))
+        assertTrue(html.contains("<meta property=\"og:music:album\" content=\"Test Album\" />"))
+        assertTrue(html.contains("<meta property=\"og:music:album:disc\" content=\"1\" />"))
+        assertTrue(html.contains("<meta property=\"og:music:album:track\" content=\"5\" />"))
+        assertTrue(html.contains("<meta property=\"og:music:musician\" content=\"Musician 1\" />"))
+        assertTrue(html.contains("<meta property=\"og:music:musician\" content=\"Musician 2\" />"))
+    }
+
+    @Test
+    fun `test generate with music album`() {
+        // Create a Data object with music.album metadata
+        val data = Data(
+            tags = emptyList(),
+            title = "Test Album",
+            type = "music.album",
+            url = URI("https://example.com/album").toURL(),
+            description = null,
+            siteName = null,
+            determiner = null,
+            locale = null,
+            localeAlternate = emptyList(),
+            images = emptyList(),
+            videos = emptyList(),
+            audios = emptyList(),
+            article = null,
+            profile = null,
+            book = null,
+            musicSong = null,
+            musicAlbum = MusicAlbum(
+                songs = listOf("Song 1", "Song 2"),
+                songDisc = 1,
+                songTrack = 1,
+                musician = listOf("Musician 1", "Musician 2"),
+                releaseDate = OffsetDateTime.parse("2023-01-01T00:00:00Z")
+            ),
+            musicPlaylist = null,
+            musicRadioStation = null,
+            videoMovie = null,
+            videoEpisode = null
+        )
+
+        val html = generator.generate(data)
+
+        // Verify that all music.album tags are generated correctly
+        assertTrue(html.contains("<meta property=\"og:music:song\" content=\"Song 1\" />"))
+        assertTrue(html.contains("<meta property=\"og:music:song\" content=\"Song 2\" />"))
+        assertTrue(html.contains("<meta property=\"og:music:song:disc\" content=\"1\" />"))
+        assertTrue(html.contains("<meta property=\"og:music:song:track\" content=\"1\" />"))
+        assertTrue(html.contains("<meta property=\"og:music:musician\" content=\"Musician 1\" />"))
+        assertTrue(html.contains("<meta property=\"og:music:musician\" content=\"Musician 2\" />"))
+        assertTrue(html.contains("<meta property=\"og:music:release_date\" content=\"2023-01-01T00:00:00Z\" />"))
+    }
+
+    @Test
+    fun `test generate with music playlist`() {
+        // Create a Data object with music.playlist metadata
+        val data = Data(
+            tags = emptyList(),
+            title = "Test Playlist",
+            type = "music.playlist",
+            url = URI("https://example.com/playlist").toURL(),
+            description = null,
+            siteName = null,
+            determiner = null,
+            locale = null,
+            localeAlternate = emptyList(),
+            images = emptyList(),
+            videos = emptyList(),
+            audios = emptyList(),
+            article = null,
+            profile = null,
+            book = null,
+            musicSong = null,
+            musicAlbum = null,
+            musicPlaylist = MusicPlaylist(
+                songs = listOf("Song 1", "Song 2"),
+                songDisc = 1,
+                songTrack = 1,
+                creator = "Playlist Creator"
+            ),
+            musicRadioStation = null,
+            videoMovie = null,
+            videoEpisode = null
+        )
+
+        val html = generator.generate(data)
+
+        // Verify that all music.playlist tags are generated correctly
+        assertTrue(html.contains("<meta property=\"og:music:song\" content=\"Song 1\" />"))
+        assertTrue(html.contains("<meta property=\"og:music:song\" content=\"Song 2\" />"))
+        assertTrue(html.contains("<meta property=\"og:music:song:disc\" content=\"1\" />"))
+        assertTrue(html.contains("<meta property=\"og:music:song:track\" content=\"1\" />"))
+        assertTrue(html.contains("<meta property=\"og:music:creator\" content=\"Playlist Creator\" />"))
+    }
+
+    @Test
+    fun `test generate with music radio station`() {
+        // Create a Data object with music.radio_station metadata
+        val data = Data(
+            tags = emptyList(),
+            title = "Test Radio Station",
+            type = "music.radio_station",
+            url = URI("https://example.com/radio").toURL(),
+            description = null,
+            siteName = null,
+            determiner = null,
+            locale = null,
+            localeAlternate = emptyList(),
+            images = emptyList(),
+            videos = emptyList(),
+            audios = emptyList(),
+            article = null,
+            profile = null,
+            book = null,
+            musicSong = null,
+            musicAlbum = null,
+            musicPlaylist = null,
+            musicRadioStation = MusicRadioStation(
+                creator = "Radio Station Creator"
+            ),
+            videoMovie = null,
+            videoEpisode = null
+        )
+
+        val html = generator.generate(data)
+
+        // Verify that all music.radio_station tags are generated correctly
+        assertTrue(html.contains("<meta property=\"og:music:creator\" content=\"Radio Station Creator\" />"))
+    }
+
+    @Test
+    fun `test generate with video episode`() {
+        // Create a Data object with video.episode metadata
+        val data = Data(
+            tags = emptyList(),
+            title = "Test Episode",
+            type = "video.episode",
+            url = URI("https://example.com/episode").toURL(),
+            description = null,
+            siteName = null,
+            determiner = null,
+            locale = null,
+            localeAlternate = emptyList(),
+            images = emptyList(),
+            videos = emptyList(),
+            audios = emptyList(),
+            article = null,
+            profile = null,
+            book = null,
+            musicSong = null,
+            musicAlbum = null,
+            musicPlaylist = null,
+            musicRadioStation = null,
+            videoMovie = null,
+            videoEpisode = VideoEpisode(
+                actors = listOf("Actor 1", "Actor 2"),
+                director = listOf("Director"),
+                writer = listOf("Writer 1", "Writer 2"),
+                duration = 45,
+                releaseDate = OffsetDateTime.parse("2023-01-01T00:00:00Z"),
+                tags = listOf("drama", "comedy"),
+                series = "Test Series"
+            )
+        )
+
+        val html = generator.generate(data)
+
+        // Verify that all video.episode tags are generated correctly
+        assertTrue(html.contains("<meta property=\"og:video:actor\" content=\"Actor 1\" />"))
+        assertTrue(html.contains("<meta property=\"og:video:actor\" content=\"Actor 2\" />"))
+        assertTrue(html.contains("<meta property=\"og:video:director\" content=\"Director\" />"))
+        assertTrue(html.contains("<meta property=\"og:video:writer\" content=\"Writer 1\" />"))
+        assertTrue(html.contains("<meta property=\"og:video:writer\" content=\"Writer 2\" />"))
+        assertTrue(html.contains("<meta property=\"og:video:duration\" content=\"45\" />"))
+        assertTrue(html.contains("<meta property=\"og:video:release_date\" content=\"2023-01-01T00:00:00Z\" />"))
+        assertTrue(html.contains("<meta property=\"og:video:tag\" content=\"drama\" />"))
+        assertTrue(html.contains("<meta property=\"og:video:tag\" content=\"comedy\" />"))
+        assertTrue(html.contains("<meta property=\"og:video:series\" content=\"Test Series\" />"))
+    }
+
+    @Test
+    fun `test generate with null values`() {
+        // Create a Data object with null values
+        val data = Data(
+            tags = emptyList(),
+            title = "Test Null Values",
+            type = "website",
+            url = URI("https://example.com").toURL(),
+            description = null,
+            siteName = null,
+            determiner = null,
+            locale = null,
+            localeAlternate = emptyList(),
+            images = emptyList(),
+            videos = emptyList(),
+            audios = emptyList(),
+            article = null,
+            profile = null,
+            book = null,
+            musicSong = null,
+            musicAlbum = null,
+            musicPlaylist = null,
+            musicRadioStation = null,
+            videoMovie = null,
+            videoEpisode = null
+        )
+
+        val html = generator.generate(data)
+
+        // Verify that only non-null values are included
+        assertTrue(html.contains("<meta property=\"og:title\" content=\"Test Null Values\" />"))
+        assertTrue(html.contains("<meta property=\"og:type\" content=\"website\" />"))
+        assertTrue(html.contains("<meta property=\"og:url\" content=\"https://example.com\" />"))
+
+        // These should not be in the output
+        assertEquals(false, html.contains("og:description"))
+        assertEquals(false, html.contains("og:site_name"))
+        assertEquals(false, html.contains("og:determiner"))
+        assertEquals(false, html.contains("og:locale"))
+    }
+
+    @Test
+    fun `test generate with empty collections`() {
+        // Create a Data object with empty collections
+        val data = Data(
+            tags = emptyList(),
+            title = "Test Empty Collections",
+            type = "article",
+            url = URI("https://example.com").toURL(),
+            description = null,
+            siteName = null,
+            determiner = null,
+            locale = null,
+            localeAlternate = emptyList(),
+            images = emptyList(),
+            videos = emptyList(),
+            audios = emptyList(),
+            article = Article(
+                publishedTime = null,
+                modifiedTime = null,
+                expirationTime = null,
+                authors = emptyList(),
+                section = null,
+                tags = emptyList()
+            ),
+            profile = null,
+            book = null,
+            musicSong = null,
+            musicAlbum = null,
+            musicPlaylist = null,
+            musicRadioStation = null,
+            videoMovie = null,
+            videoEpisode = null
+        )
+
+        val html = generator.generate(data)
+
+        // Verify that empty collections don't generate any tags
+        assertTrue(html.contains("<meta property=\"og:title\" content=\"Test Empty Collections\" />"))
+        assertTrue(html.contains("<meta property=\"og:type\" content=\"article\" />"))
+        assertTrue(html.contains("<meta property=\"og:url\" content=\"https://example.com\" />"))
+
+        // These should not be in the output
+        assertEquals(false, html.contains("og:article:published_time"))
+        assertEquals(false, html.contains("og:article:modified_time"))
+        assertEquals(false, html.contains("og:article:expiration_time"))
+        assertEquals(false, html.contains("og:article:author"))
+        assertEquals(false, html.contains("og:article:section"))
+        assertEquals(false, html.contains("og:article:tag"))
+    }
+
+    @Test
+    fun `test format date time`() {
+        // Create a Data object with date time values
+        val data = Data(
+            tags = emptyList(),
+            title = "Test Date Time",
+            type = "article",
+            url = URI("https://example.com").toURL(),
+            description = null,
+            siteName = null,
+            determiner = null,
+            locale = null,
+            localeAlternate = emptyList(),
+            images = emptyList(),
+            videos = emptyList(),
+            audios = emptyList(),
+            article = Article(
+                publishedTime = OffsetDateTime.parse("2023-01-01T12:34:56+01:00"),
+                modifiedTime = OffsetDateTime.parse("2023-01-02T00:00:00Z"),
+                expirationTime = OffsetDateTime.parse("2023-12-31T23:59:59-08:00"),
+                authors = emptyList(),
+                section = null,
+                tags = emptyList()
+            ),
+            profile = null,
+            book = null,
+            musicSong = null,
+            musicAlbum = null,
+            musicPlaylist = null,
+            musicRadioStation = null,
+            videoMovie = null,
+            videoEpisode = null
+        )
+
+        val html = generator.generate(data)
+
+        // Verify that date time values are formatted correctly
+        // The formatDateTime method converts to UTC/Z time
+        assertTrue(html.contains("<meta property=\"og:article:published_time\" content=\"2023-01-01T11:34:56Z\" />"))
+        assertTrue(html.contains("<meta property=\"og:article:modified_time\" content=\"2023-01-02T00:00:00Z\" />"))
+        assertTrue(html.contains("<meta property=\"og:article:expiration_time\" content=\"2024-01-01T07:59:59Z\" />"))
+    }
+
     @Test
     fun `test round trip conversion`() {
         // Create a sample HTML with OpenGraph tags
@@ -326,4 +769,4 @@ class GeneratorTest {
         assertTrue(generatedHtml.contains("<meta property=\"og:image\" content=\"https://example.com/rock.jpg\" />"))
         assertTrue(generatedHtml.contains("<meta property=\"og:description\" content=\"An action movie about a rock\" />"))
     }
-}
\ No newline at end of file
+}