diff --git a/build.gradle.kts b/build.gradle.kts
index 042bf4cf0..a53b0fb23 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -231,7 +231,8 @@ val experimentalAnnotations = arrayOf(
     "kotlin.experimental.ExperimentalTypeInference",
     "net.mamoe.mirai.utils.MiraiInternalAPI",
     "net.mamoe.mirai.utils.MiraiExperimentalAPI",
-    "net.mamoe.mirai.LowLevelAPI"
+    "net.mamoe.mirai.LowLevelAPI",
+    "kotlinx.serialization.ExperimentalSerializationApi"
 )
 
 fun Project.configureKotlinExperimentalUsages() {
diff --git a/mirai-core-api/src/commonMain/kotlin/contact/Exceptions.kt b/mirai-core-api/src/commonMain/kotlin/contact/Exceptions.kt
index 989462056..2388674c2 100644
--- a/mirai-core-api/src/commonMain/kotlin/contact/Exceptions.kt
+++ b/mirai-core-api/src/commonMain/kotlin/contact/Exceptions.kt
@@ -13,6 +13,7 @@ package net.mamoe.mirai.contact
 
 import net.mamoe.mirai.message.data.Message
 import net.mamoe.mirai.utils.asHumanReadable
+import kotlin.time.ExperimentalTime
 import kotlin.time.seconds
 
 /**
@@ -38,6 +39,7 @@ public class MessageTooLargeException(
  *
  * @see Group.sendMessage
  */
+@OptIn(ExperimentalTime::class)
 public class BotIsBeingMutedException(
     public val target: Group
 ) : RuntimeException("bot is being muted, remaining ${target.botMuteRemaining.seconds.asHumanReadable} seconds")
diff --git a/mirai-core-api/src/commonMain/kotlin/message/data/CustomMessage.kt b/mirai-core-api/src/commonMain/kotlin/message/data/CustomMessage.kt
index fb416cecb..cd8856442 100644
--- a/mirai-core-api/src/commonMain/kotlin/message/data/CustomMessage.kt
+++ b/mirai-core-api/src/commonMain/kotlin/message/data/CustomMessage.kt
@@ -209,6 +209,7 @@ internal inline fun <T : CustomMessageMetadata> T.customToStringImpl(factory: Cu
     return (factory as CustomMessage.Factory<T>).dump(this)
 }
 
+@OptIn(ExperimentalUnsignedTypes::class)
 @JvmOverloads
 @Suppress("DuplicatedCode") // false positive. foreach is not common to UByteArray and ByteArray
 internal fun ByteArray.toUHexString(
diff --git a/mirai-core-api/src/jvmTest/java/net/mamoe/mirai/event/JvmMethodEventsTestJava.java b/mirai-core-api/src/jvmTest/java/net/mamoe/mirai/event/JvmMethodEventsTestJava.java
index 9f7e0a1e5..3cd8058fa 100644
--- a/mirai-core-api/src/jvmTest/java/net/mamoe/mirai/event/JvmMethodEventsTestJava.java
+++ b/mirai-core-api/src/jvmTest/java/net/mamoe/mirai/event/JvmMethodEventsTestJava.java
@@ -9,7 +9,7 @@
 
 package net.mamoe.mirai.event;
 
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 import java.util.concurrent.atomic.AtomicInteger;
 
diff --git a/mirai-core-api/src/jvmTest/kotlin/event/CancelScopeTest.kt b/mirai-core-api/src/jvmTest/kotlin/event/CancelScopeTest.kt
index 949a59b19..05c97841c 100644
--- a/mirai-core-api/src/jvmTest/kotlin/event/CancelScopeTest.kt
+++ b/mirai-core-api/src/jvmTest/kotlin/event/CancelScopeTest.kt
@@ -11,7 +11,7 @@ package net.mamoe.mirai.event
 import kotlinx.coroutines.*
 import net.mamoe.mirai.event.broadcast
 import net.mamoe.mirai.event.subscribeAlways
-import org.junit.Test
+import org.junit.jupiter.api.Test
 import kotlin.test.assertFalse
 
 
diff --git a/mirai-core-api/src/jvmTest/kotlin/event/JvmMethodEventsTest.kt b/mirai-core-api/src/jvmTest/kotlin/event/JvmMethodEventsTest.kt
index d53a8cd24..30a917590 100644
--- a/mirai-core-api/src/jvmTest/kotlin/event/JvmMethodEventsTest.kt
+++ b/mirai-core-api/src/jvmTest/kotlin/event/JvmMethodEventsTest.kt
@@ -14,7 +14,7 @@ import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.runBlocking
 import net.mamoe.mirai.event.*
 import org.jetbrains.annotations.NotNull
-import org.junit.Test
+import org.junit.jupiter.api.Test
 import java.util.concurrent.atomic.AtomicInteger
 import kotlin.coroutines.EmptyCoroutineContext
 import kotlin.test.assertEquals
diff --git a/mirai-core-api/src/jvmTest/kotlin/utils/LockFreeLinkedListTest.kt b/mirai-core-api/src/jvmTest/kotlin/utils/LockFreeLinkedListTest.kt
index b6b4eb833..c60eea92e 100644
--- a/mirai-core-api/src/jvmTest/kotlin/utils/LockFreeLinkedListTest.kt
+++ b/mirai-core-api/src/jvmTest/kotlin/utils/LockFreeLinkedListTest.kt
@@ -145,6 +145,7 @@ internal class LockFreeLinkedListTest {
         list.size shouldBeEqualTo 0
     }
 
+    @OptIn(ExperimentalUnsignedTypes::class)
     @Test
     fun withInlineClassElements() {
         val list = LockFreeLinkedList<UInt>()
diff --git a/mirai-core/src/jvmTest/java/SimpleListenerHostTest.java b/mirai-core/src/jvmTest/java/net/mamoe/mirai/javatest/SimpleListenerHostTest.java
similarity index 71%
rename from mirai-core/src/jvmTest/java/SimpleListenerHostTest.java
rename to mirai-core/src/jvmTest/java/net/mamoe/mirai/javatest/SimpleListenerHostTest.java
index 422e925ba..faf12d2b5 100644
--- a/mirai-core/src/jvmTest/java/SimpleListenerHostTest.java
+++ b/mirai-core/src/jvmTest/java/net/mamoe/mirai/javatest/SimpleListenerHostTest.java
@@ -1,9 +1,12 @@
 /*
- * Copyright 2020 Mamoe Technologies and contributors.
- * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
- * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
  *
- * https://github.com/mamoe/mirai/blob/master/LICENSE
+ *  * Copyright 2020 Mamoe Technologies and contributors.
+ *  *
+ *  * 此源代码的使用受 GNU AFFERO GENERAL PUBLIC LICENSE version 3 许可证的约束, 可以在以下链接找到该许可证.
+ *  * Use of this source code is governed by the GNU AGPLv3 license that can be found through the following link.
+ *  *
+ *  * https://github.com/mamoe/mirai/blob/master/LICENSE
+ *
  */
 
 package net.mamoe.mirai.javatest;
@@ -12,7 +15,7 @@ import kotlin.coroutines.EmptyCoroutineContext;
 import kotlinx.coroutines.CoroutineScope;
 import kotlinx.coroutines.CoroutineScopeKt;
 import net.mamoe.mirai.event.*;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 import java.util.concurrent.atomic.AtomicBoolean;