diff --git a/src/test/kotlin/dev/usbharu/hideout/routing/activitypub/InboxRoutingKtTest.kt b/src/test/kotlin/dev/usbharu/hideout/routing/activitypub/InboxRoutingKtTest.kt
index 05f8596f..106eae24 100644
--- a/src/test/kotlin/dev/usbharu/hideout/routing/activitypub/InboxRoutingKtTest.kt
+++ b/src/test/kotlin/dev/usbharu/hideout/routing/activitypub/InboxRoutingKtTest.kt
@@ -7,13 +7,21 @@ import com.fasterxml.jackson.databind.DeserializationFeature
 import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
 import dev.usbharu.hideout.plugins.configureRouting
 import dev.usbharu.hideout.plugins.configureSerialization
+import dev.usbharu.hideout.plugins.configureStatusPages
+import dev.usbharu.hideout.service.activitypub.ActivityPubService
+import dev.usbharu.hideout.service.activitypub.ActivityPubUserService
+import dev.usbharu.hideout.service.impl.UserService
+import dev.usbharu.hideout.service.signature.HttpSignatureVerifyService
 import io.ktor.client.request.*
 import io.ktor.client.statement.*
 import io.ktor.http.*
 import io.ktor.server.config.*
 import io.ktor.server.testing.*
+import junit.framework.TestCase.assertEquals
 import org.junit.jupiter.api.Assertions
 import org.junit.jupiter.api.Test
+import org.mockito.kotlin.any
+import org.mockito.kotlin.doReturn
 import org.mockito.kotlin.mock
 
 class InboxRoutingKtTest {
@@ -30,4 +38,25 @@ class InboxRoutingKtTest {
             Assertions.assertEquals(HttpStatusCode.MethodNotAllowed, it.status)
         }
     }
+
+    @Test
+    fun `sharedInboxに空のリクエストボディでPOSTしたら400が帰ってくる`() = testApplication {
+        environment {
+            config = ApplicationConfig("empty.conf")
+        }
+        val httpSignatureVerifyService = mock<HttpSignatureVerifyService>{
+            on { verify(any()) } doReturn true
+        }
+        val activityPubService = mock<ActivityPubService>()
+        val userService = mock<UserService>()
+        val activityPubUserService = mock<ActivityPubUserService>()
+        application {
+            configureStatusPages()
+            configureSerialization()
+            configureRouting(httpSignatureVerifyService, activityPubService, userService, activityPubUserService)
+        }
+        client.post("/inbox").let {
+            Assertions.assertEquals(HttpStatusCode.BadRequest, it.status)
+        }
+    }
 }