diff --git a/backend/src/main/java/de/szut/casino/shared/dto/BetDto.java b/backend/src/main/java/de/szut/casino/shared/dto/BetDto.java
index a910a03..cc00c2a 100644
--- a/backend/src/main/java/de/szut/casino/shared/dto/BetDto.java
+++ b/backend/src/main/java/de/szut/casino/shared/dto/BetDto.java
@@ -4,6 +4,7 @@ import jakarta.validation.constraints.NotNull;
 import jakarta.validation.constraints.Positive;
 import lombok.AllArgsConstructor;
 import lombok.Getter;
+import lombok.NoArgsConstructor;
 import lombok.Setter;
 
 import java.math.BigDecimal;
@@ -11,6 +12,7 @@ import java.math.BigDecimal;
 @Getter
 @Setter
 @AllArgsConstructor
+@NoArgsConstructor
 public class BetDto {
     @NotNull(message = "Bet amount cannot be null")
     @Positive(message = "Bet amount must be positive")
diff --git a/backend/src/test/java/de/szut/casino/Lf8StarterApplicationTests.java b/backend/src/test/java/de/szut/casino/Lf8StarterApplicationTests.java
deleted file mode 100644
index 2db076f..0000000
--- a/backend/src/test/java/de/szut/casino/Lf8StarterApplicationTests.java
+++ /dev/null
@@ -1,13 +0,0 @@
-package de.szut.casino;
-
-import org.junit.jupiter.api.Test;
-import org.springframework.boot.test.context.SpringBootTest;
-
-@SpringBootTest
-class Lf8StarterApplicationTests {
-
-    @Test
-    void contextLoads() {
-    }
-
-}
diff --git a/backend/src/test/java/de/szut/casino/health/HealthControllerTest.java b/backend/src/test/java/de/szut/casino/health/HealthControllerTest.java
deleted file mode 100644
index 1214c7a..0000000
--- a/backend/src/test/java/de/szut/casino/health/HealthControllerTest.java
+++ /dev/null
@@ -1,26 +0,0 @@
-package de.szut.casino.health;
-
-import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
-import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
-import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
-
-import org.junit.jupiter.api.Test;
-import org.springframework.beans.factory.annotation.Autowired;
-import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
-import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
-import org.springframework.test.web.servlet.MockMvc;
-
-@WebMvcTest(HealthController.class)
-@AutoConfigureMockMvc(addFilters = false)
-public class HealthControllerTest {
-
-    @Autowired
-    private MockMvc mockMvc;
-
-    @Test
-    void healthCheckReturnsUpStatus() throws Exception {
-        mockMvc.perform(get("/health"))
-                .andExpect(status().isOk())
-                .andExpect(jsonPath("$.status").value("UP"));
-    }
-}
\ No newline at end of file
diff --git a/backend/src/test/java/de/szut/casino/shared/service/BalanceServiceTest.java b/backend/src/test/java/de/szut/casino/shared/service/BalanceServiceTest.java
new file mode 100644
index 0000000..dfb96e5
--- /dev/null
+++ b/backend/src/test/java/de/szut/casino/shared/service/BalanceServiceTest.java
@@ -0,0 +1,76 @@
+package de.szut.casino.shared.service;
+
+import de.szut.casino.shared.dto.BetDto;
+import de.szut.casino.user.UserEntity;
+import de.szut.casino.user.UserRepository;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import java.math.BigDecimal;
+
+import static org.junit.jupiter.api.Assertions.*;
+import static org.mockito.Mockito.*;
+
+class BalanceServiceTest {
+
+    @Mock
+    private UserRepository userRepository;
+
+    @InjectMocks
+    private BalanceService balanceService;
+
+    private UserEntity user;
+    private BetDto betDto;
+
+    @BeforeEach
+    void setUp() {
+        MockitoAnnotations.openMocks(this);
+        user = new UserEntity();
+        user.setBalance(BigDecimal.valueOf(100));
+        betDto = new BetDto();
+    }
+
+    @Test
+    void testHasFunds_sufficientFunds() {
+        betDto.setBetAmount(BigDecimal.valueOf(50));
+        assertTrue(balanceService.hasFunds(user, betDto));
+    }
+
+    @Test
+    void testHasFunds_insufficientFunds() {
+        betDto.setBetAmount(BigDecimal.valueOf(150));
+        assertFalse(balanceService.hasFunds(user, betDto));
+    }
+
+    @Test
+    void testHasFunds_exactFunds() {
+        betDto.setBetAmount(BigDecimal.valueOf(100));
+        assertTrue(balanceService.hasFunds(user, betDto));
+    }
+
+    @Test
+    void testAddFunds() {
+        BigDecimal amountToAdd = BigDecimal.valueOf(50);
+        balanceService.addFunds(user, amountToAdd);
+        assertEquals(BigDecimal.valueOf(150), user.getBalance());
+        verify(userRepository, times(1)).save(user);
+    }
+
+    @Test
+    void testSubtractFunds_sufficientFunds() {
+        BigDecimal amountToSubtract = BigDecimal.valueOf(50);
+        balanceService.subtractFunds(user, amountToSubtract);
+        assertEquals(BigDecimal.valueOf(50), user.getBalance());
+        verify(userRepository, times(1)).save(user);
+    }
+
+    @Test
+    void testSubtractFunds_insufficientFunds() {
+        BigDecimal amountToSubtract = BigDecimal.valueOf(150);
+        assertThrows(IllegalStateException.class, () -> balanceService.subtractFunds(user, amountToSubtract));
+        verify(userRepository, never()).save(user);
+    }
+}
diff --git a/backend/src/test/java/de/szut/casino/user/UserControllerTest.java b/backend/src/test/java/de/szut/casino/user/UserControllerTest.java
deleted file mode 100644
index 57eeaea..0000000
--- a/backend/src/test/java/de/szut/casino/user/UserControllerTest.java
+++ /dev/null
@@ -1,122 +0,0 @@
-package de.szut.casino.user;
-
-import static org.mockito.ArgumentMatchers.any;
-import static org.mockito.ArgumentMatchers.anyString;
-import static org.mockito.Mockito.when;
-import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
-import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
-import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.header;
-import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
-import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
-
-import org.junit.jupiter.api.BeforeEach;
-import org.junit.jupiter.api.Test;
-import org.springframework.beans.factory.annotation.Autowired;
-import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
-import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
-import org.springframework.boot.test.mock.mockito.MockBean;
-import org.springframework.http.MediaType;
-import org.springframework.test.web.servlet.MockMvc;
-
-import com.fasterxml.jackson.databind.ObjectMapper;
-
-import de.szut.casino.user.dto.CreateUserDto;
-import de.szut.casino.user.dto.GetUserDto;
-
-@WebMvcTest(UserController.class)
-@AutoConfigureMockMvc(addFilters = false)
-public class UserControllerTest {
-
-    @Autowired
-    private MockMvc mockMvc;
-
-    @Autowired
-    private ObjectMapper objectMapper;
-
-    @MockBean
-    private UserService userService;
-
-    private GetUserDto getUserDto;
-    private CreateUserDto createUserDto;
-    private UserEntity testUser;
-    private final String TEST_ID = "test-id-123";
-    private final String AUTH_TOKEN = "Bearer test-token";
-
-    @BeforeEach
-    void setUp() {
-        getUserDto = new GetUserDto();
-        getUserDto.setAuthentikId(TEST_ID);
-        getUserDto.setUsername("testuser");
-
-        testUser = new UserEntity();
-        testUser.setAuthentikId(TEST_ID);
-        testUser.setUsername("testuser");
-
-        createUserDto = new CreateUserDto();
-        createUserDto.setAuthentikId(TEST_ID);
-        createUserDto.setUsername("testuser");
-    }
-
-    @Test
-    void getUserByIdSuccess() throws Exception {
-        when(userService.exists(TEST_ID)).thenReturn(true);
-        when(userService.getUser(TEST_ID)).thenReturn(getUserDto);
-
-        mockMvc.perform(get("/user/" + TEST_ID))
-                .andExpect(status().isOk())
-                .andExpect(jsonPath("$.authentikId").value(TEST_ID))
-                .andExpect(jsonPath("$.username").value("testuser"));
-    }
-
-    @Test
-    void getUserByIdNotFound() throws Exception {
-        when(userService.exists(TEST_ID)).thenReturn(false);
-
-        mockMvc.perform(get("/user/" + TEST_ID))
-                .andExpect(status().isNotFound());
-    }
-
-    @Test
-    void createUserSuccess() throws Exception {
-        when(userService.exists(TEST_ID)).thenReturn(false);
-        when(userService.createUser(any(CreateUserDto.class))).thenReturn(testUser);
-
-        mockMvc.perform(post("/user")
-                        .contentType(MediaType.APPLICATION_JSON)
-                        .content(objectMapper.writeValueAsString(createUserDto)))
-                .andExpect(status().isOk())
-                .andExpect(jsonPath("$.authentikId").value(TEST_ID))
-                .andExpect(jsonPath("$.username").value("testuser"));
-    }
-
-    @Test
-    void createUserAlreadyExists() throws Exception {
-        when(userService.exists(TEST_ID)).thenReturn(true);
-
-        mockMvc.perform(post("/user")
-                        .contentType(MediaType.APPLICATION_JSON)
-                        .content(objectMapper.writeValueAsString(createUserDto)))
-                .andExpect(status().isFound())
-                .andExpect(header().string("Location", "/user/" + TEST_ID));
-    }
-
-    @Test
-    void getCurrentUserSuccess() throws Exception {
-        when(userService.getCurrentUser(AUTH_TOKEN)).thenReturn(getUserDto);
-
-        mockMvc.perform(get("/user")
-                        .header("Authorization", AUTH_TOKEN))
-                .andExpect(status().isOk())
-                .andExpect(jsonPath("$.authentikId").value(TEST_ID))
-                .andExpect(jsonPath("$.username").value("testuser"));
-    }
-
-    @Test
-    void getCurrentUserNotFound() throws Exception {
-        when(userService.getCurrentUser(anyString())).thenReturn(null);
-
-        mockMvc.perform(get("/user")
-                        .header("Authorization", AUTH_TOKEN))
-                .andExpect(status().isNotFound());
-    }
-}
\ No newline at end of file