fix(language-detection): 최초 감지 캐시 경합을 직렬화한다

src/test/kotlin/kr/co/vividnext/sodalive/content/LanguageDetectionCacheServiceTest.kt

@@ -2,6 +2,7 @@ package kr.co.vividnext.sodalive.content
 
 import kr.co.vividnext.sodalive.i18n.translation.SourceTextNormalizer
 import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.DisplayName
 import org.junit.jupiter.api.Test
 import org.mockito.Mockito
 
@@ -37,6 +38,67 @@ class LanguageDetectionCacheServiceTest {
 
         assertEquals("en", detected)
         assertEquals(0, providerCalls)
-        Mockito.verify(repository, Mockito.never()).save(Mockito.any(LanguageDetectionResult::class.java))
+        Mockito.verify(repository).findBySourceHashAndProviderAndNormalizationVersion(
+            sourceHash = sourceHash,
+            provider = "papago",
+            normalizationVersion = SourceTextNormalizer.NORMALIZATION_VERSION
+        )
+        Mockito.verifyNoMoreInteractions(repository)
+    }
+
+    @Test
+    @DisplayName("최초 캐시 저장 경합에서는 저장된 승자의 감지 언어를 반환한다")
+    fun shouldReturnStoredWinnerAfterInitialCacheInsert() {
+        val repository = Mockito.mock(LanguageDetectionResultRepository::class.java)
+        val service = LanguageDetectionCacheService(repository)
+        val sourceHash = SourceTextNormalizer.hash("Hello world")
+
+        Mockito.`when`(
+            repository.findBySourceHashAndProviderAndNormalizationVersion(
+                sourceHash = sourceHash,
+                provider = "papago",
+                normalizationVersion = SourceTextNormalizer.NORMALIZATION_VERSION
+            )
+        ).thenReturn(null)
+        Mockito.`when`(
+            repository.insertIfAbsent(
+                sourceHash = sourceHash,
+                sourceTextSample = "Hello world",
+                detectedLanguage = "en",
+                provider = "papago",
+                confidence = null,
+                normalizationVersion = SourceTextNormalizer.NORMALIZATION_VERSION
+            )
+        ).thenReturn(0)
+        Mockito.`when`(
+            repository.findDetectedLanguageForUpdate(
+                sourceHash = sourceHash,
+                provider = "papago",
+                normalizationVersion = SourceTextNormalizer.NORMALIZATION_VERSION
+            )
+        ).thenReturn("ko")
+
+        val detected = service.detectWithCache("Hello world") { "en" }
+
+        assertEquals("ko", detected)
+        Mockito.verify(repository).findBySourceHashAndProviderAndNormalizationVersion(
+            sourceHash = sourceHash,
+            provider = "papago",
+            normalizationVersion = SourceTextNormalizer.NORMALIZATION_VERSION
+        )
+        Mockito.verify(repository).insertIfAbsent(
+            sourceHash = sourceHash,
+            sourceTextSample = "Hello world",
+            detectedLanguage = "en",
+            provider = "papago",
+            confidence = null,
+            normalizationVersion = SourceTextNormalizer.NORMALIZATION_VERSION
+        )
+        Mockito.verify(repository).findDetectedLanguageForUpdate(
+            sourceHash = sourceHash,
+            provider = "papago",
+            normalizationVersion = SourceTextNormalizer.NORMALIZATION_VERSION
+        )
+        Mockito.verifyNoMoreInteractions(repository)
     }
 }