diff --git a/build.gradle b/build.gradle
index 35c7fdbaae..01f8be4cd9 100644
--- a/build.gradle
+++ b/build.gradle
@@ -39,6 +39,8 @@ dependencies {
 
     api "io.ktor:ktor-server:$ktor_version"
     api "io.ktor:ktor-server-host-common:$ktor_version"
+
+    testImplementation "org.jetbrains.kotlin:kotlin-test-junit:$kotlin_version"
 }
 
 compileKotlin {
diff --git a/src/test/kotlin/com/github/insanusmokrassar/TelegramBotAPI/types/ChatIdentifierTests.kt b/src/test/kotlin/com/github/insanusmokrassar/TelegramBotAPI/types/ChatIdentifierTests.kt
new file mode 100644
index 0000000000..df568f6a74
--- /dev/null
+++ b/src/test/kotlin/com/github/insanusmokrassar/TelegramBotAPI/types/ChatIdentifierTests.kt
@@ -0,0 +1,79 @@
+package com.github.insanusmokrassar.TelegramBotAPI.types
+
+import kotlinx.serialization.ImplicitReflectionSerializer
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.Json
+import kotlin.test.*
+
+@ImplicitReflectionSerializer
+private const val chatIdentifierChatId: Identifier = 123L
+@ImplicitReflectionSerializer
+private const val chatIdentifierLink = "tg://user?id=$chatIdentifierChatId"
+@ImplicitReflectionSerializer
+private const val testUsername = "@Example"
+
+@ImplicitReflectionSerializer
+class ChatIdentifierTests {
+    @Test
+    fun `Cast from Int to ChatId is working correctly`() {
+        val chatId = chatIdentifierChatId.toInt().toChatId()
+        assertEquals(chatIdentifierChatId, chatId.chatId)
+    }
+    @Test
+    fun `Cast from Byte to ChatId is working correctly`() {
+        val chatId = chatIdentifierChatId.toByte().toChatId()
+        assertEquals(chatIdentifierChatId, chatId.chatId)
+    }
+    @Test
+    fun `Cast from Identifier to ChatId is working correctly`() {
+        val chatId = chatIdentifierChatId.toChatId()
+        assertEquals(chatIdentifierChatId, chatId.chatId)
+    }
+
+    @Test
+    fun `Creating link from ChatId is correct`() {
+        val chatId = chatIdentifierChatId.toChatId()
+        assertEquals(chatIdentifierLink, chatId.link)
+    }
+
+    @Test
+    fun `Cast from String to Username is working correctly`() {
+        assertEquals(testUsername, testUsername.toUsername().username)
+
+        assertFails("Username creating must fail when trying to create from string which is not starting from @ symbol") {
+            testUsername.replace("@", "").toUsername().username
+        }
+    }
+
+
+    @Test
+    fun `Deserializing from String must work correctly`() {
+        @Serializable
+        data class Example(
+            val identifier: ChatIdentifier
+        )
+
+        Example(chatIdentifierChatId.toChatId()).let { withChatId ->
+            val stringified = Json.plain.stringify(Example.serializer(), withChatId)
+            assertEquals(stringified, "{\"identifier\":\"$chatIdentifierChatId\"}")
+            val deserialized = Json.plain.parse(Example.serializer(), stringified)
+            assertEquals(withChatId, deserialized)
+        }
+
+        Example(testUsername.toUsername()).let { withUsername ->
+            val stringified = Json.plain.stringify(Example.serializer(), withUsername)
+            assertEquals(stringified, "{\"identifier\":\"$testUsername\"}")
+            val deserialized = Json.plain.parse(Example.serializer(), stringified)
+            assertEquals(withUsername, deserialized)
+        }
+
+        // Replace @ by empty string, because from time to time we can retrieve from Telegram system
+        // username without starting @ symbol
+        Example(testUsername.toUsername()).let { withUsername ->
+            val stringified = Json.plain.stringify(Example.serializer(), withUsername).replace("@", "")
+            assertEquals(stringified, "{\"identifier\":\"${testUsername.replace("@", "")}\"}")
+            val deserialized = Json.plain.parse(Example.serializer(), stringified)
+            assertEquals(withUsername, deserialized)
+        }
+    }
+}