feat: restructure tests and included concurrency tests

src/main/java/com/example/settlementsenrichment/entity/MarketSettlementMessage.java

@@ -1,6 +1,7 @@
 package com.example.settlementsenrichment.entity;
 
 import com.example.settlementsenrichment.util.ValidationConstants;
+import com.fasterxml.jackson.annotation.JsonIgnore;
 import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 import io.swagger.v3.oas.annotations.media.Schema;
 import jakarta.persistence.*;
@@ -72,4 +73,8 @@ public class MarketSettlementMessage {
     @Column(name = "supporting_information")
     @Schema(type = "String", example = "/BNF/FFC-4697132")
     private String supportingInformation;
+
+    @Version
+    @JsonIgnore
+    private Integer version;
 }

src/main/java/com/example/settlementsenrichment/exception/GlobalExceptionHandler.java

@@ -1,5 +1,6 @@
 package com.example.settlementsenrichment.exception;
 
+import org.hibernate.exception.LockAcquisitionException;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
 import org.springframework.http.converter.HttpMessageNotReadableException;
@@ -66,6 +67,15 @@ public ResponseEntity<ErrorResponse> handleHttpMessageNotReadableException(HttpM
         return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(errorResponse);
     }
 
+    @ExceptionHandler(LockAcquisitionException.class)
+    public ResponseEntity<ErrorResponse> handleLockAcquisitionException(LockAcquisitionException ex) {
+        Map<String, String> errors = new HashMap<>();
+        errors.put("detail", "Database lock acquisition failure");
+
+        ErrorResponse errorResponse = new ErrorResponse(HttpStatus.CONFLICT.value(), "Database conflict error", errors);
+        return ResponseEntity.status(HttpStatus.CONFLICT).body(errorResponse);
+    }
+
     @ExceptionHandler(Exception.class)
     public ResponseEntity<ErrorResponse> handleGlobalException(Exception ex, WebRequest request) {
         ErrorResponse errorResponse = new ErrorResponse(HttpStatus.INTERNAL_SERVER_ERROR.value(), "An unexpected error occurred");

src/main/java/com/example/settlementsenrichment/service/MarketSettlementMessageService.java

@@ -11,6 +11,7 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Isolation;
 import org.springframework.transaction.annotation.Transactional;
 
 import java.math.RoundingMode;
@@ -28,7 +29,7 @@ public MarketSettlementMessageService(MarketSettlementMessageRepository marketSe
         this.standardSettlementInstructionRepository = standardSettlementInstructionRepository;
     }
 
-    @Transactional
+    @Transactional(isolation = Isolation.SERIALIZABLE)
     public MarketSettlementMessage createMarketSettlementMessage(TradeRequest tradeRequest) {
 
         if (findOptionalByTradeId(tradeRequest.tradeId()).isPresent()) {

src/test/java/com/example/settlementsenrichment/integration/MarketSettlementMessageConcurrentWriteTest.java

@@ -0,0 +1,70 @@
+package com.example.settlementsenrichment.integration;
+
+import com.example.settlementsenrichment.AbstractIntegrationTest;
+import com.example.settlementsenrichment.dto.TradeRequest;
+import com.example.settlementsenrichment.entity.MarketSettlementMessage;
+import com.example.settlementsenrichment.entity.StandardSettlementInstruction;
+import com.example.settlementsenrichment.repository.MarketSettlementMessageRepository;
+import com.example.settlementsenrichment.repository.StandardSettlementInstructionRepository;
+import com.example.settlementsenrichment.service.MarketSettlementMessageService;
+import org.hibernate.exception.LockAcquisitionException;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+
+import java.math.BigDecimal;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class MarketSettlementMessageConcurrentWriteTest extends AbstractIntegrationTest {
+
+    @Autowired
+    private StandardSettlementInstructionRepository standardSettlementInstructionRepository;
+
+    @Autowired
+    private MarketSettlementMessageRepository marketSettlementMessageRepository;
+
+    @Autowired
+    private MarketSettlementMessageService marketSettlementMessageService;
+
+    @BeforeEach
+    void setUp() {
+        standardSettlementInstructionRepository.deleteAll();
+
+        StandardSettlementInstruction ssi = StandardSettlementInstruction.builder()
+                .code("OCBC_DBS_1")
+                .payerAccountNumber("438421")
+                .payerBank("OCBCSGSGXXX")
+                .receiverAccountNumber("05461368")
+                .receiverBank("DBSSGB2LXXX")
+                .supportingInformation("BNF:FFC-4697132")
+                .build();
+
+        standardSettlementInstructionRepository.save(ssi);
+    }
+
+    @Test
+    void testConcurrentWrites() throws ExecutionException {
+        TradeRequest tradeRequest1 = new TradeRequest("16846548", "OCBC_DBS_1", new BigDecimal("12894.65"), "USD", "20022020");
+        TradeRequest tradeRequest2 = new TradeRequest("16846548", "OCBC_DBS_1", new BigDecimal("12894.65"), "USD", "20022020");
+
+        CompletableFuture<MarketSettlementMessage> future1 = CompletableFuture.supplyAsync(() -> marketSettlementMessageService.createMarketSettlementMessage(tradeRequest1));
+        CompletableFuture<MarketSettlementMessage> future2 = CompletableFuture.supplyAsync(() -> marketSettlementMessageService.createMarketSettlementMessage(tradeRequest2));
+
+        ExecutionException exception = assertThrows(ExecutionException.class, () -> {
+            CompletableFuture.allOf(future1, future2).get();
+        });
+
+        Throwable cause = exception.getCause();
+        assertNotNull(cause);
+        assertNotNull(cause.getCause());
+        assertEquals(LockAcquisitionException.class, cause.getCause().getClass(), "Expected LockAcquisitionException");
+
+        List<MarketSettlementMessage> messages = marketSettlementMessageRepository.findAll();
+        assertEquals(1, messages.size(), "Only one MarketSettlementMessage should exist with the given tradeId");
+        assertEquals("16846548", messages.get(0).getTradeId());
+    }
+}

src/test/java/com/example/settlementsenrichment/integration/MarketSettlementMessageControllerIntTest.java → src/test/java/com/example/settlementsenrichment/integration/controller/MarketSettlementMessageControllerIntTest.java

@@ -1,4 +1,4 @@
-package com.example.settlementsenrichment.integration;
+package com.example.settlementsenrichment.integration.controller;
 
 import com.example.settlementsenrichment.AbstractIntegrationTest;
 import com.example.settlementsenrichment.entity.MarketSettlementMessage;

src/test/java/com/example/settlementsenrichment/controller/MarketSettlementMessageControllerTest.java → src/test/java/com/example/settlementsenrichment/unit/controller/MarketSettlementMessageControllerTest.java

@@ -1,5 +1,6 @@
-package com.example.settlementsenrichment.controller;
+package com.example.settlementsenrichment.unit.controller;
 
+import com.example.settlementsenrichment.controller.MarketSettlementMessageController;
 import com.example.settlementsenrichment.dto.TradeRequest;
 import com.example.settlementsenrichment.entity.MarketSettlementMessage;
 import com.example.settlementsenrichment.entity.Party;

src/test/java/com/example/settlementsenrichment/service/MarketSettlementMessageServiceTest.java → src/test/java/com/example/settlementsenrichment/unit/service/MarketSettlementMessageServiceTest.java

@@ -1,4 +1,4 @@
-package com.example.settlementsenrichment.service;
+package com.example.settlementsenrichment.unit.service;
 
 import com.example.settlementsenrichment.dto.TradeRequest;
 import com.example.settlementsenrichment.entity.MarketSettlementMessage;
@@ -8,6 +8,7 @@
 import com.example.settlementsenrichment.exception.ResourceNotFoundException;
 import com.example.settlementsenrichment.repository.MarketSettlementMessageRepository;
 import com.example.settlementsenrichment.repository.StandardSettlementInstructionRepository;
+import com.example.settlementsenrichment.service.MarketSettlementMessageService;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;