diff --git a/build.gradle.kts b/build.gradle.kts
index 623d128..bbf2473 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -38,6 +38,10 @@ dependencies {
     // test
     testImplementation("org.springframework.boot:spring-boot-starter-test")
     testImplementation("io.projectreactor:reactor-test")
+    testImplementation("io.kotest:kotest-runner-junit5:5.4.2")
+    testImplementation("io.kotest:kotest-assertions-core:5.4.2")
+    testImplementation("io.kotest.extensions:kotest-extensions-spring:1.1.2")
+    testImplementation("io.mockk:mockk:1.13.8")
 
     // security
     implementation("org.springframework.boot:spring-boot-starter-security")
diff --git a/src/test/kotlin/com/trip/safe/user/service/UserServiceTest.kt b/src/test/kotlin/com/trip/safe/user/service/UserServiceTest.kt
new file mode 100644
index 0000000..86b89f6
--- /dev/null
+++ b/src/test/kotlin/com/trip/safe/user/service/UserServiceTest.kt
@@ -0,0 +1,43 @@
+package com.trip.safe.user.service
+
+import com.trip.safe.common.security.jwt.JwtTokenProvider
+import com.trip.safe.user.domain.User
+import com.trip.safe.user.domain.UserRepository
+import com.trip.safe.user.exception.UserExistException
+import com.trip.safe.user.presentation.dto.request.UserSignUpRequest
+import io.kotest.core.spec.style.DescribeSpec
+import io.mockk.coEvery
+import io.mockk.coVerify
+import io.mockk.mockk
+import org.junit.jupiter.api.assertDoesNotThrow
+import org.junit.jupiter.api.assertThrows
+import org.springframework.security.crypto.password.PasswordEncoder
+
+class UserServiceTest : DescribeSpec(
+    {
+        val userRepository = mockk<UserRepository>(relaxed = true)
+        val jwtTokenProvider = mockk<JwtTokenProvider>(relaxed = true)
+        val passwordEncoder = mockk<PasswordEncoder>(relaxed = true)
+        val userService = UserService(userRepository, jwtTokenProvider, passwordEncoder)
+        val requestStub = UserSignUpRequest("testAccountId", "testPassword", 20)
+
+        describe("유저가 회원가입을 하는 경우") {
+            context("이미 존재하는 유저이면") {
+                coEvery { userRepository.existsByAccountId(requestStub.accountId) } returns true
+                it("UserExistException을 던진다.") {
+                    assertThrows<UserExistException> { userService.signUp(requestStub) }
+                    coVerify(exactly = 0) { userRepository.save(any()) }
+                }
+            }
+
+            context("존재하지 않는 유저이면") {
+                coEvery { userRepository.existsByAccountId(requestStub.accountId) } returns false
+                coEvery { passwordEncoder.encode(requestStub.password) } returns requestStub.password
+                it("회원가입에 성공한다.") {
+                    assertDoesNotThrow { userService.signUp(requestStub) }
+                    coVerify(exactly = 1) { userRepository.save(any()) }
+                }
+            }
+        }
+    }
+)