Maintenance: ApiResponse - Add comprehensive test coverage

src/test/java/spring/memewikibe/support/response/ApiResponseTest.java

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+package spring.memewikibe.support.response;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+import spring.memewikibe.annotation.UnitTest;
+import spring.memewikibe.support.error.ErrorMessage;
+import spring.memewikibe.support.error.ErrorType;
+
+import static org.assertj.core.api.BDDAssertions.then;
+
+@UnitTest
+class ApiResponseTest {
+
+    @Nested
+    @DisplayName("success() 메서드는")
+    class SuccessMethod {
+
+        @Test
+        @DisplayName("데이터 없이 성공 응답을 생성한다")
+        void createSuccessResponseWithoutData() {
+            // when
+            ApiResponse<?> response = ApiResponse.success();
+
+            // then
+            then(response.getResultType()).isEqualTo(ResultType.SUCCESS);
+            then(response.getSuccess()).isNull();
+            then(response.getError()).isNull();
+        }
+
+        @Test
+        @DisplayName("데이터와 함께 성공 응답을 생성한다")
+        void createSuccessResponseWithData() {
+            // given
+            String data = "test data";
+
+            // when
+            ApiResponse<String> response = ApiResponse.success(data);
+
+            // then
+            then(response.getResultType()).isEqualTo(ResultType.SUCCESS);
+            then(response.getSuccess()).isEqualTo(data);
+            then(response.getError()).isNull();
+        }
+
+        @Test
+        @DisplayName("null 데이터로 성공 응답을 생성한다")
+        void createSuccessResponseWithNullData() {
+            // when
+            ApiResponse<String> response = ApiResponse.success(null);
+
+            // then
+            then(response.getResultType()).isEqualTo(ResultType.SUCCESS);
+            then(response.getSuccess()).isNull();
+            then(response.getError()).isNull();
+        }
+
+        @Test
+        @DisplayName("복잡한 객체로 성공 응답을 생성한다")
+        void createSuccessResponseWithComplexObject() {
+            // given
+            TestData testData = new TestData("name", 123);
+
+            // when
+            ApiResponse<TestData> response = ApiResponse.success(testData);
+
+            // then
+            then(response.getResultType()).isEqualTo(ResultType.SUCCESS);
+            then(response.getSuccess()).isEqualTo(testData);
+            then(response.getError()).isNull();
+        }
+    }
+
+    @Nested
+    @DisplayName("error() 메서드는")
+    class ErrorMethod {
+
+        @Test
+        @DisplayName("ErrorType만으로 에러 응답을 생성한다")
+        void createErrorResponseWithErrorType() {
+            // given
+            ErrorType errorType = ErrorType.MEME_NOT_FOUND;
+
+            // when
+            ApiResponse<?> response = ApiResponse.error(errorType);
+
+            // then
+            then(response.getResultType()).isEqualTo(ResultType.ERROR);
+            then(response.getSuccess()).isNull();
+            then(response.getError()).isNotNull();
+            then(response.getError().code()).isEqualTo(errorType.getCode().name());
+            then(response.getError().message()).isEqualTo(errorType.getMessage());
+            then(response.getError().data()).isNull();
+        }
+
+        @Test
+        @DisplayName("ErrorType과 추가 데이터로 에러 응답을 생성한다")
+        void createErrorResponseWithErrorTypeAndData() {
+            // given
+            ErrorType errorType = ErrorType.EXTERNAL_SERVICE_BAD_REQUEST;
+            String errorData = "Invalid request format";
+
+            // when
+            ApiResponse<?> response = ApiResponse.error(errorType, errorData);
+
+            // then
+            then(response.getResultType()).isEqualTo(ResultType.ERROR);
+            then(response.getSuccess()).isNull();
+            then(response.getError()).isNotNull();
+            then(response.getError().code()).isEqualTo(errorType.getCode().name());
+            then(response.getError().message()).isEqualTo(errorType.getMessage());
+            then(response.getError().data()).isEqualTo(errorData);
+        }
+
+        @Test
+        @DisplayName("다양한 ErrorType으로 에러 응답을 생성한다")
+        void createErrorResponseWithDifferentErrorTypes() {
+            // when & then
+            ApiResponse<?> notFoundResponse = ApiResponse.error(ErrorType.MEME_NOT_FOUND);
+            then(notFoundResponse.getError().code()).isEqualTo("E404");
+
+            ApiResponse<?> internalErrorResponse = ApiResponse.error(ErrorType.DEFAULT_ERROR);
+            then(internalErrorResponse.getError().code()).isEqualTo("E500");
+
+            ApiResponse<?> serviceErrorResponse = ApiResponse.error(ErrorType.EXTERNAL_SERVICE_ERROR);
+            then(serviceErrorResponse.getError().code()).isEqualTo("E503");
+        }
+
+        @Test
+        @DisplayName("복잡한 객체를 에러 데이터로 사용할 수 있다")
+        void createErrorResponseWithComplexErrorData() {
+            // given
+            ErrorType errorType = ErrorType.EXTERNAL_SERVICE_BAD_REQUEST;
+            TestData errorData = new TestData("field", 42);
+
+            // when
+            ApiResponse<?> response = ApiResponse.error(errorType, errorData);
+
+            // then
+            then(response.getResultType()).isEqualTo(ResultType.ERROR);
+            then(response.getError()).isNotNull();
+            then(response.getError().data()).isEqualTo(errorData);
+        }
+
+        @Test
+        @DisplayName("null을 에러 데이터로 사용할 수 있다")
+        void createErrorResponseWithNullErrorData() {
+            // given
+            ErrorType errorType = ErrorType.DEFAULT_ERROR;
+
+            // when
+            ApiResponse<?> response = ApiResponse.error(errorType, null);
+
+            // then
+            then(response.getResultType()).isEqualTo(ResultType.ERROR);
+            then(response.getError()).isNotNull();
+            then(response.getError().data()).isNull();
+        }
+    }
+
+    @Nested
+    @DisplayName("ApiResponse는")
+    class ApiResponseSemantics {
+
+        @Test
+        @DisplayName("성공 응답은 에러 필드가 null이다")
+        void successResponseHasNullError() {
+            // when
+            ApiResponse<?> emptySuccess = ApiResponse.success();
+            ApiResponse<String> dataSuccess = ApiResponse.success("data");
+
+            // then
+            then(emptySuccess.getError()).isNull();
+            then(dataSuccess.getError()).isNull();
+        }
+
+        @Test
+        @DisplayName("에러 응답은 성공 필드가 null이다")
+        void errorResponseHasNullSuccess() {
+            // when
+            ApiResponse<?> errorResponse1 = ApiResponse.error(ErrorType.MEME_NOT_FOUND);
+            ApiResponse<?> errorResponse2 = ApiResponse.error(ErrorType.DEFAULT_ERROR, "data");
+
+            // then
+            then(errorResponse1.getSuccess()).isNull();
+            then(errorResponse2.getSuccess()).isNull();
+        }
+
+        @Test
+        @DisplayName("성공 응답의 resultType은 SUCCESS다")
+        void successResponseHasSuccessResultType() {
+            // when
+            ApiResponse<?> response = ApiResponse.success("data");
+
+            // then
+            then(response.getResultType()).isEqualTo(ResultType.SUCCESS);
+        }
+
+        @Test
+        @DisplayName("에러 응답의 resultType은 ERROR다")
+        void errorResponseHasErrorResultType() {
+            // when
+            ApiResponse<?> response = ApiResponse.error(ErrorType.MEME_NOT_FOUND);
+
+            // then
+            then(response.getResultType()).isEqualTo(ResultType.ERROR);
+        }
+    }
+
+    @Nested
+    @DisplayName("ErrorMessage 통합 테스트")
+    class ErrorMessageIntegration {
+
+        @Test
+        @DisplayName("ApiResponse의 에러는 올바른 ErrorMessage 구조를 가진다")
+        void errorResponseHasCorrectErrorMessageStructure() {
+            // given
+            ErrorType errorType = ErrorType.CATEGORY_NOT_FOUND;
+            String additionalData = "category-id-123";
+
+            // when
+            ApiResponse<?> response = ApiResponse.error(errorType, additionalData);
+
+            // then
+            ErrorMessage error = response.getError();
+            then(error).isNotNull();
+            then(error.code()).isEqualTo(errorType.getCode().name());
+            then(error.message()).isEqualTo(errorType.getMessage());
+            then(error.data()).isEqualTo(additionalData);
+        }
+    }
+
+    // Test fixture
+    record TestData(String name, int value) {}
+}