diff --git a/backend/src/test/java/springweb/backend/ClientServiceTest.java b/backend/src/test/java/springweb/backend/ClientServiceTest.java
index 7294c4f..3fee854 100644
--- a/backend/src/test/java/springweb/backend/ClientServiceTest.java
+++ b/backend/src/test/java/springweb/backend/ClientServiceTest.java
@@ -1,6 +1,8 @@
 package springweb.backend;
+
 import org.junit.jupiter.api.Test;
 
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Optional;
 
@@ -8,19 +10,19 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.mockito.Mockito.*;
 
-public class ClientServiceTest {
+class ClientServiceTest {
 
     private final ClientRepository mockUserRepo = mock(ClientRepository.class);
 
     @Test
-    public void GetAllClients_Test() {
+    void GetAllClients_Test() {
         // GIVEN
-        GroceryProduct product = new GroceryProduct("1", "Fruit", "Apple", 0.99, 1,"test-status" ,"apple.jpg");
+        GroceryProduct product = new GroceryProduct("1", "Fruit", "Apple", 0.99, 1, "test-status", "apple.jpg");
         List<GroceryProduct> shoppingList1 = List.of(product);
         Client expectedClient1 = new Client("123", shoppingList1);
 
-        GroceryProduct product2 = new GroceryProduct("2", "Fruit", "Banana", 500, 1,"test-status" ,"banane.jpg");
-        GroceryProduct product3 = new GroceryProduct("3", "Fruit", "Kiwi", 1.80, 1,"test-status" ,"ps5.jpg");
+        GroceryProduct product2 = new GroceryProduct("2", "Fruit", "Banana", 500, 1, "test-status", "banane.jpg");
+        GroceryProduct product3 = new GroceryProduct("3", "Fruit", "Kiwi", 1.80, 1, "test-status", "ps5.jpg");
         List<GroceryProduct> shoppingList2 = List.of(product2, product3);
         Client expectedClient2 = new Client("456", shoppingList2);
 
@@ -38,9 +40,9 @@ public void GetAllClients_Test() {
     }
 
     @Test
-    public void GetClientById_Test() {
+    void GetClientById_Test() {
         // GIVEN
-        GroceryProduct product = new GroceryProduct("1", "Fruit", "Apple", 0.99, 1,"test-status" ,"apple.jpg");
+        GroceryProduct product = new GroceryProduct("1", "Fruit", "Apple", 0.99, 1, "test-status", "apple.jpg");
         List<GroceryProduct> shoppingList = List.of(product);
         Client expectedClient = new Client("123", shoppingList);
 
@@ -55,4 +57,118 @@ public void GetClientById_Test() {
         assertTrue(result.isPresent());
         assertEquals(expectedClient, result.get());
     }
+
+    @Test
+    void addGroceryProductToClient_Test() {
+        // GIVEN
+        GroceryProduct product1 = new GroceryProduct("1", "Fruit", "Apple", 0.99, 1, "test-status", "apple.jpg");
+        List<GroceryProduct> oldShoppingList = new ArrayList<>();
+        oldShoppingList.add(product1);
+        Client oldClient = new Client("123", oldShoppingList);
+
+        GroceryProduct product2 = new GroceryProduct("2", "Fruit", "Banana", 500, 1, "test-status", "banana.jpg");
+        List<GroceryProduct> newShoppingList = new ArrayList<>(oldShoppingList);
+        newShoppingList.add(product2);
+        Client newClient = new Client("123", newShoppingList);
+
+        when(mockUserRepo.existsById("123")).thenReturn(true);
+        when(mockUserRepo.findById("123")).thenReturn(Optional.of(oldClient));
+        when(mockUserRepo.save(oldClient)).thenReturn(newClient);
+        ClientService clientService = new ClientService(mockUserRepo);
+
+        // WHEN
+        Client actual = clientService.addGroceryProductToClient(product2, "123");
+
+        // THEN
+        verify(mockUserRepo).existsById("123");
+        verify(mockUserRepo).findById("123");
+        verify(mockUserRepo).save(oldClient);
+
+        assertEquals(2, actual.shoppingList().size());
+        assertEquals(product2, actual.shoppingList().get(1));
+    }
+
+    @Test
+    void addClient_Test() {
+        //GIVEN
+
+        //WHEN
+
+        //THEN
+    }
+
+    @Test
+    void updateClient_Test() {
+        // GIVEN
+        GroceryProduct product2 = new GroceryProduct("2", "Fruit", "Banana", 500, 1, "test-status", "banana.jpg");
+        List<GroceryProduct> newShoppingList = List.of(product2);
+        Client clientDto = new Client("123", newShoppingList);
+        Client updatedClient = new Client("123", newShoppingList);
+
+        when(mockUserRepo.existsById("123")).thenReturn(true);
+        when(mockUserRepo.save(updatedClient)).thenReturn(updatedClient);
+        ClientService clientService = new ClientService(mockUserRepo);
+
+        // WHEN
+        Client result = clientService.updateClient("123", clientDto);
+
+        // THEN
+        verify(mockUserRepo).existsById("123");
+        verify(mockUserRepo).save(updatedClient);
+        assertEquals(updatedClient, result);
+        assertEquals("123", result.id());
+        assertEquals(newShoppingList, result.shoppingList());
+    }
+
+    @Test
+    void deleteClientById_Test() {
+        // GIVEN
+        String clientId = "123";
+
+        when(mockUserRepo.existsById(clientId)).thenReturn(true);
+        ClientService clientService = new ClientService(mockUserRepo);
+
+        // WHEN
+        boolean result = clientService.deleteClientById(clientId);
+
+        // THEN
+        verify(mockUserRepo).existsById(clientId);
+        verify(mockUserRepo).deleteById(clientId);
+        assertTrue(result);
+    }
+
+    @Test
+    void deleteProductByIdFromClientByIdClient_Test() {
+        // GIVEN
+        String clientId = "123";
+        String productIdToDelete = "2";
+
+        GroceryProduct product1 = new GroceryProduct("1", "Fruit", "Apple", 0.99, 1, "test-status", "apple.jpg");
+        GroceryProduct product2 = new GroceryProduct("2", "Fruit", "Banana", 500, 1, "test-status", "banana.jpg");
+        List<GroceryProduct> shoppingList = new ArrayList<>(List.of(product1, product2));
+        Client client = new Client(clientId, shoppingList);
+
+        when(mockUserRepo.existsById(clientId)).thenReturn(true);
+        when(mockUserRepo.findById(clientId)).thenReturn(Optional.of(client));
+        ClientService clientService = new ClientService(mockUserRepo);
+
+        // WHEN
+        clientService.deleteProductByIdFromClientById(clientId, productIdToDelete);
+
+        // THEN
+        assertEquals(1, client.shoppingList().size());
+        assertEquals("1", client.shoppingList().get(0).id()); // Only product1 should remain
+        verify(mockUserRepo).existsById(clientId);
+        verify(mockUserRepo).findById(clientId);
+        verify(mockUserRepo).save(client);
+    }
+
+    @Test
+    void changeProductByIdFromClientById_Test() {
+        //GIVEN
+
+        //WHEN
+
+        //THEN
+    }
 }
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