diff --git a/hideout-core/src/test/kotlin/dev/usbharu/hideout/core/application/actor/GetActorDetailApplicationServiceTest.kt b/hideout-core/src/test/kotlin/dev/usbharu/hideout/core/application/actor/GetActorDetailApplicationServiceTest.kt
new file mode 100644
index 00000000..b8c61847
--- /dev/null
+++ b/hideout-core/src/test/kotlin/dev/usbharu/hideout/core/application/actor/GetActorDetailApplicationServiceTest.kt
@@ -0,0 +1,160 @@
+package dev.usbharu.hideout.core.application.actor
+
+import dev.usbharu.hideout.core.config.ApplicationConfig
+import dev.usbharu.hideout.core.domain.model.actor.ActorId
+import dev.usbharu.hideout.core.domain.model.actor.ActorRepository
+import dev.usbharu.hideout.core.domain.model.actor.TestActorFactory
+import dev.usbharu.hideout.core.domain.model.media.*
+import dev.usbharu.hideout.core.domain.model.support.acct.Acct
+import dev.usbharu.hideout.core.domain.model.support.principal.Anonymous
+import kotlinx.coroutines.test.runTest
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.assertThrows
+import org.junit.jupiter.api.extension.ExtendWith
+import org.mockito.InjectMocks
+import org.mockito.Mock
+import org.mockito.Spy
+import org.mockito.junit.jupiter.MockitoExtension
+import org.mockito.kotlin.*
+import utils.TestTransaction
+import java.net.URI
+
+@ExtendWith(MockitoExtension::class)
+class GetActorDetailApplicationServiceTest {
+
+    @InjectMocks
+    lateinit var service: GetActorDetailApplicationService
+
+    @Mock
+    lateinit var actorRepository: ActorRepository
+
+    @Mock
+    lateinit var mediaRepository: MediaRepository
+
+    @Spy
+    val applicationConfig = ApplicationConfig(URI.create("http://localhost:8081").toURL())
+
+    @Spy
+    val transaction = TestTransaction
+
+    @Test
+    fun idとname両方nullならエラー() = runTest {
+        assertThrows<IllegalArgumentException> {
+            service.execute(GetActorDetail(null, null), Anonymous)
+        }
+    }
+
+    @Test
+    fun idがnullじゃない場合idから取得() = runTest {
+        val actor = TestActorFactory.create(id = 1)
+        whenever(actorRepository.findById(ActorId(1))).doReturn(actor)
+
+        val actual = service.execute(GetActorDetail(null, 1), Anonymous)
+
+        assertEquals(actual, ActorDetail.of(actor, null, null))
+    }
+
+    @Test
+    fun idが存在しないとエラー() = runTest {
+        assertThrows<IllegalArgumentException> {
+            service.execute(GetActorDetail(null, 2), Anonymous)
+        }
+    }
+
+    @Test
+    fun idがnullでacctがnullじゃない場合acctから取得() = runTest {
+        val actor = TestActorFactory.create(actorName = "test", domain = "example.com")
+        whenever(actorRepository.findByNameAndDomain("test", "example.com")).thenReturn(actor)
+
+        val actual = service.execute(GetActorDetail(Acct("test", "example.com"), null), Anonymous)
+
+        assertEquals(actual, ActorDetail.of(actor, null, null))
+    }
+
+    @Test
+    fun acctのhostが空ならローカルのhostが使われる() = runTest {
+        val actor = TestActorFactory.create(actorName = "test", domain = "localhost")
+        whenever(actorRepository.findByNameAndDomain("test", "localhost")).thenReturn(actor)
+
+        val actual = service.execute(GetActorDetail(Acct("test", ""), null), Anonymous)
+
+        assertEquals(actual, ActorDetail.of(actor, null, null))
+    }
+
+    @Test
+    fun acctが存在しないとエラー() = runTest {
+        assertThrows<IllegalArgumentException> {
+            service.execute(GetActorDetail(Acct("test", "example.com"), null), Anonymous)
+        }
+    }
+
+    @Test
+    fun idとacctがnullじゃない場合idが優先される() = runTest {
+        val actor = TestActorFactory.create(id = 1)
+        whenever(actorRepository.findById(ActorId(1))).doReturn(actor)
+
+        val actual = service.execute(GetActorDetail(null, 1), Anonymous)
+
+        assertEquals(actual, ActorDetail.of(actor, null, null))
+        verify(actorRepository, never()).findByNameAndDomain(any(), any())
+    }
+
+    @Test
+    fun iconがnullじゃない時取得する() = runTest {
+        val actor = TestActorFactory.create(id = 1, icon = 1)
+        whenever(actorRepository.findById(ActorId(1))).doReturn(actor)
+        whenever(mediaRepository.findById(MediaId(1))).doReturn(
+            Media(
+                id = MediaId(1),
+                name = MediaName(""),
+                url = URI.create("http://example.com"),
+                remoteUrl = null,
+                thumbnailUrl = null,
+                type = FileType.Image,
+                mimeType = MimeType("image", "jpeg", FileType.Image),
+                blurHash = null,
+                description = null,
+                actorId = ActorId(1)
+            )
+        )
+
+        val actual = service.execute(GetActorDetail(null, 1), Anonymous)
+
+        assertEquals(actual, ActorDetail.of(actor, URI.create("http://example.com"), null))
+    }
+
+    @Test
+    fun bannerがnullじゃない時取得する() = runTest {
+        val actor = TestActorFactory.create(id = 1, banner = 1)
+        whenever(actorRepository.findById(ActorId(1))).doReturn(actor)
+        whenever(mediaRepository.findById(MediaId(1))).doReturn(
+            Media(
+                id = MediaId(1),
+                name = MediaName(""),
+                url = URI.create("http://example.com"),
+                remoteUrl = null,
+                thumbnailUrl = null,
+                type = FileType.Image,
+                mimeType = MimeType("image", "jpeg", FileType.Image),
+                blurHash = null,
+                description = null,
+                actorId = ActorId(1)
+            )
+        )
+
+        val actual = service.execute(GetActorDetail(null, 1), Anonymous)
+
+        assertEquals(actual, ActorDetail.of(actor, null, URI.create("http://example.com")))
+    }
+
+    @Test
+    fun iconとbannerが見つからなかった場合null() = runTest {
+        val actor = TestActorFactory.create(id = 1, icon = 1, banner = 1)
+        whenever(actorRepository.findById(ActorId(1))).doReturn(actor)
+
+        val actual = service.execute(GetActorDetail(null, 1), Anonymous)
+
+        assertEquals(actual, ActorDetail.of(actor, null, null))
+    }
+}
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