diff --git a/CHANGELOG.md b/CHANGELOG.md
index 91bd7b183d..9f05e77f22 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,8 @@
 
 ## 0.38.18
 
+* `Core`:
+    * Add support of test servers (fix of [#577](https://github.com/InsanusMokrassar/TelegramBotAPI/issues/577))
 * `BehaviourBuilder`:
     * Fixes in extension `BehaviourContext#doInSubContextWithUpdatesFilter` (thanks to [xzima](https://github.com/xzima))
 
diff --git a/tgbotapi.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/BotBuilder.kt b/tgbotapi.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/BotBuilder.kt
index ba33c8425f..b83b9a9f01 100644
--- a/tgbotapi.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/BotBuilder.kt
+++ b/tgbotapi.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/BotBuilder.kt
@@ -40,8 +40,9 @@ data class BotBuilder internal constructor(
 fun buildBot(
     token: String,
     apiUrl: String = telegramBotAPIDefaultUrl,
+    testServer: Boolean = false,
     block: BotBuilder.() -> Unit
 ) = telegramBot(
-    TelegramAPIUrlsKeeper(token, apiUrl),
+    TelegramAPIUrlsKeeper(token, testServer, apiUrl),
     BotBuilder().apply(block).createHttpClient()
 )
diff --git a/tgbotapi.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/BotExtensions.kt b/tgbotapi.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/BotExtensions.kt
index 4390ab619b..d47d8d85af 100644
--- a/tgbotapi.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/BotExtensions.kt
+++ b/tgbotapi.api/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/api/BotExtensions.kt
@@ -66,17 +66,19 @@ inline fun telegramBot(
 inline fun telegramBot(
     token: String,
     apiUrl: String = telegramBotAPIDefaultUrl,
+    testServer: Boolean = false,
     client: HttpClient = HttpClient()
-): TelegramBot = telegramBot(TelegramAPIUrlsKeeper(token, apiUrl), client)
+): TelegramBot = telegramBot(TelegramAPIUrlsKeeper(token, testServer, apiUrl), client)
 
 @Suppress("NOTHING_TO_INLINE")
 inline fun <T: HttpClientEngineConfig> telegramBot(
     token: String,
     clientFactory: HttpClientEngineFactory<T>,
     apiUrl: String = telegramBotAPIDefaultUrl,
+    testServer: Boolean = false,
     noinline clientConfig: HttpClientConfig<T>.() -> Unit = {}
 ) = telegramBot(
-    TelegramAPIUrlsKeeper(token, apiUrl),
+    TelegramAPIUrlsKeeper(token, testServer, apiUrl),
     clientFactory,
     clientConfig
 )
@@ -90,9 +92,10 @@ inline fun telegramBot(
     token: String,
     clientEngine: HttpClientEngine,
     apiUrl: String = telegramBotAPIDefaultUrl,
+    testServer: Boolean = false,
     noinline clientConfig: HttpClientConfig<*>.() -> Unit = {}
 ) = telegramBot(
-    TelegramAPIUrlsKeeper(token, apiUrl),
+    TelegramAPIUrlsKeeper(token, testServer, apiUrl),
     clientEngine,
     clientConfig
 )
@@ -105,8 +108,9 @@ inline fun telegramBot(
 inline fun telegramBot(
     token: String,
     apiUrl: String = telegramBotAPIDefaultUrl,
+    testServer: Boolean = false,
     noinline clientConfig: HttpClientConfig<*>.() -> Unit
 ) = telegramBot(
-    TelegramAPIUrlsKeeper(token, apiUrl),
+    TelegramAPIUrlsKeeper(token, testServer, apiUrl),
     clientConfig
 )
diff --git a/tgbotapi.behaviour_builder.fsm/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/behaviour_builder/TelegramBotWithFSM.kt b/tgbotapi.behaviour_builder.fsm/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/behaviour_builder/TelegramBotWithFSM.kt
index 0c5b881580..edfc67de48 100644
--- a/tgbotapi.behaviour_builder.fsm/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/behaviour_builder/TelegramBotWithFSM.kt
+++ b/tgbotapi.behaviour_builder.fsm/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/behaviour_builder/TelegramBotWithFSM.kt
@@ -38,10 +38,12 @@ suspend fun <T : State> telegramBotWithBehaviourAndFSM(
     defaultExceptionsHandler: ExceptionHandler<Unit>? = null,
     statesManager: StatesManager<T> = DefaultStatesManager(InMemoryDefaultStatesManagerRepo()),
     presetHandlers: MutableList<BehaviourWithFSMStateHandlerHolder<*, T>> = mutableListOf(),
+    testServer: Boolean = false,
     block: CustomBehaviourContextReceiver<BehaviourContextWithFSMBuilder<T>, Unit>
 ): TelegramBot = telegramBot(
     token,
     apiUrl,
+    testServer,
     builder
 ).apply {
     buildBehaviourWithFSMAndStartLongPolling(
@@ -73,11 +75,13 @@ suspend fun <T : State> telegramBotWithBehaviourAndFSMAndStartLongPolling(
     defaultExceptionsHandler: ExceptionHandler<Unit>? = null,
     statesManager: StatesManager<T> = DefaultStatesManager(InMemoryDefaultStatesManagerRepo()),
     presetHandlers: MutableList<BehaviourWithFSMStateHandlerHolder<*, T>> = mutableListOf(),
+    testServer: Boolean = false,
     block: CustomBehaviourContextReceiver<BehaviourContextWithFSMBuilder<T>, Unit>
 ): Pair<TelegramBot, Job> {
     return telegramBot(
         token,
         apiUrl,
+        testServer,
         builder
     ).let {
         it to it.buildBehaviourWithFSMAndStartLongPolling (
diff --git a/tgbotapi.behaviour_builder/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/behaviour_builder/TelegramBot.kt b/tgbotapi.behaviour_builder/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/behaviour_builder/TelegramBot.kt
index 6ab989cd08..ddc0bdb704 100644
--- a/tgbotapi.behaviour_builder/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/behaviour_builder/TelegramBot.kt
+++ b/tgbotapi.behaviour_builder/src/commonMain/kotlin/dev/inmo/tgbotapi/extensions/behaviour_builder/TelegramBot.kt
@@ -30,10 +30,12 @@ suspend fun telegramBotWithBehaviour(
     apiUrl: String = telegramBotAPIDefaultUrl,
     builder: KtorRequestsExecutorBuilder.() -> Unit = {},
     defaultExceptionsHandler: ExceptionHandler<Unit>? = null,
+    testServer: Boolean = false,
     block: BehaviourContextReceiver<Unit>
 ): TelegramBot = telegramBot(
     token,
     apiUrl,
+    testServer,
     builder
 ).apply {
     buildBehaviour(
@@ -63,11 +65,13 @@ suspend fun telegramBotWithBehaviourAndLongPolling(
     apiUrl: String = telegramBotAPIDefaultUrl,
     builder: KtorRequestsExecutorBuilder.() -> Unit = {},
     defaultExceptionsHandler: ExceptionHandler<Unit>? = null,
+    testServer: Boolean = false,
     block: BehaviourContextReceiver<Unit>
 ): Pair<TelegramBot, Job> {
     return telegramBot(
         token,
         apiUrl,
+        testServer,
         builder
     ).let {
         it to it.buildBehaviourWithLongPolling(
diff --git a/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/bot/Ktor/KtorRequestsExecutor.kt b/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/bot/Ktor/KtorRequestsExecutor.kt
index 1e7da06255..dda3e97fde 100644
--- a/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/bot/Ktor/KtorRequestsExecutor.kt
+++ b/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/bot/Ktor/KtorRequestsExecutor.kt
@@ -125,5 +125,6 @@ inline fun telegramBot(
 inline fun telegramBot(
     token: String,
     apiUrl: String = telegramBotAPIDefaultUrl,
+    testServer: Boolean = false,
     builder: KtorRequestsExecutorBuilder.() -> Unit = {}
-): TelegramBot = telegramBot(TelegramAPIUrlsKeeper(token, apiUrl), builder)
+): TelegramBot = telegramBot(TelegramAPIUrlsKeeper(token, testServer, apiUrl), builder)
diff --git a/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/utils/TelegramAPIUrlsKeeper.kt b/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/utils/TelegramAPIUrlsKeeper.kt
index 649a8ccc2b..9960a89f02 100644
--- a/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/utils/TelegramAPIUrlsKeeper.kt
+++ b/tgbotapi.core/src/commonMain/kotlin/dev/inmo/tgbotapi/utils/TelegramAPIUrlsKeeper.kt
@@ -16,7 +16,8 @@ private inline val String.withoutLastSlash: String
 
 class TelegramAPIUrlsKeeper(
     token: String,
-    hostUrl: String = telegramBotAPIDefaultUrl
+    hostUrl: String = telegramBotAPIDefaultUrl,
+    urlsSuffixes: String = ""
 ) {
     val webAppDataSecretKey by lazy {
         token.hmacSha256("WebAppData")
@@ -25,10 +26,16 @@ class TelegramAPIUrlsKeeper(
     val commonAPIUrl: String
     val fileBaseUrl: String
 
+    constructor(token: String, testServer: Boolean, hostUrl: String = telegramBotAPIDefaultUrl) : this(
+        token,
+        hostUrl,
+        "/test".takeIf { testServer } ?: ""
+    )
+
     init {
         val correctedHost = hostUrl.withoutLastSlash
-        commonAPIUrl = "$correctedHost/bot$token"
-        fileBaseUrl = "$correctedHost/file/bot$token"
+        commonAPIUrl = "$correctedHost/bot$token$urlsSuffixes"
+        fileBaseUrl = "$correctedHost/file/bot$token$urlsSuffixes"
     }
 
     fun createFileLinkUrl(filePath: String) = "${fileBaseUrl}/$filePath"