fix(comment-nickname): deleted_ 로 시작하는 닉네임 접두사 노출을 제거한다

src/test/kotlin/kr/co/vividnext/sodalive/extensions/StringExtensionsTest.kt

@@ -0,0 +1,33 @@
+package kr.co.vividnext.sodalive.extensions
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+
+class StringExtensionsTest {
+    @Test
+    fun shouldRemoveDeletedPrefixWhenNicknameStartsWithDeletedPrefix() {
+        val nickname = "deleted_testUser"
+
+        val sanitizedNickname = nickname.removeDeletedNicknamePrefix()
+
+        assertEquals("testUser", sanitizedNickname)
+    }
+
+    @Test
+    fun shouldKeepNicknameWhenDeletedPrefixDoesNotExist() {
+        val nickname = "testUser"
+
+        val sanitizedNickname = nickname.removeDeletedNicknamePrefix()
+
+        assertEquals("testUser", sanitizedNickname)
+    }
+
+    @Test
+    fun shouldReturnEmptyStringWhenNicknameContainsOnlyDeletedPrefix() {
+        val nickname = "deleted_"
+
+        val sanitizedNickname = nickname.removeDeletedNicknamePrefix()
+
+        assertEquals("", sanitizedNickname)
+    }
+}