diff --git a/EstateManagementUI.BlazorServer.Tests/Pages/Merchants/MerchantsEditPageTests.cs b/EstateManagementUI.BlazorServer.Tests/Pages/Merchants/MerchantsEditPageTests.cs
new file mode 100644
index 00000000..e60e7ff7
--- /dev/null
+++ b/EstateManagementUI.BlazorServer.Tests/Pages/Merchants/MerchantsEditPageTests.cs
@@ -0,0 +1,788 @@
+using AngleSharp.Dom;
+using Bunit;
+using EstateManagementUI.BlazorServer.Common;
+using EstateManagementUI.BlazorServer.Models;
+using EstateManagementUI.BusinessLogic.Requests;
+using Microsoft.AspNetCore.Components.Web;
+using Moq;
+using Shouldly;
+using SimpleResults;
+using MerchantsEdit = EstateManagementUI.BlazorServer.Components.Pages.Merchants.Edit;
+
+namespace EstateManagementUI.BlazorServer.Tests.Pages.Merchants;
+
+public class MerchantsEditPageTests : BaseTest
+{
+    [Fact]
+    public void MerchantsEdit_RendersCorrectly()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        SetupSuccessfulDataLoad(merchantId);
+
+        // Act
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        
+        // Assert
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        cut.Markup.ShouldContain("Edit Merchant");
+    }
+
+    [Fact]
+    public void MerchantsEdit_HasCorrectPageTitle()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        SetupSuccessfulDataLoad(merchantId);
+
+        // Act
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        
+        // Assert
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        IRenderedComponent<PageTitle> pageTitle = cut.FindComponent<Microsoft.AspNetCore.Components.Web.PageTitle>();
+        pageTitle.Instance.ChildContent.ShouldNotBeNull();
+    }
+
+    [Fact]
+    public void MerchantsEdit_DisplaysMerchantDetails()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        SetupSuccessfulDataLoad(merchantId, "Test Merchant", "MERCH001");
+
+        // Act
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        
+        // Assert
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        cut.Markup.ShouldContain("Test Merchant");
+        cut.Markup.ShouldContain("MERCH001");
+    }
+
+    [Fact]
+    public void MerchantsEdit_BackToListButton_NavigatesToMerchantsList()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        SetupSuccessfulDataLoad(merchantId);
+
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Act - Find Back to List button and click it
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? backButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Back to List"));
+        backButton?.Click();
+        
+        // Assert
+        _fakeNavigationManager.Uri.ShouldContain("/merchants");
+    }
+
+    [Fact]
+    public void MerchantsEdit_TabSwitch_ToAddress_UpdatesActiveTab()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        SetupSuccessfulDataLoad(merchantId);
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Act - Find address button and click it
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? addressButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Address Details"));
+        addressButton?.Click();
+        
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("Address Line 1"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_TabSwitch_ToContact_UpdatesActiveTab()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        SetupSuccessfulDataLoad(merchantId);
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Act - Find contact button and click it
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? contactButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Contact Details"));
+        contactButton?.Click();
+        
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("Contact Name"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_TabSwitch_ToOperators_UpdatesActiveTab()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        SetupSuccessfulDataLoad(merchantId);
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Act - Find operators button and click it
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? operatorsButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Assigned Operators"));
+        operatorsButton?.Click();
+        
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("Assigned Operators"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_TabSwitch_ToContracts_UpdatesActiveTab()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        SetupSuccessfulDataLoad(merchantId);
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Act - Find contracts button and click it
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? contractsButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Assigned Contracts"));
+        contractsButton?.Click();
+        
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("Assigned Contracts"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_TabSwitch_ToDevices_UpdatesActiveTab()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        SetupSuccessfulDataLoad(merchantId);
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Act - Find devices button and click it
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? devicesButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Assigned Devices"));
+        devicesButton?.Click();
+        
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("Assigned Devices"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_TabSwitch_BackToDetails_UpdatesActiveTab()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        SetupSuccessfulDataLoad(merchantId);
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Switch to address first
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? addressButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Address Details"));
+        addressButton?.Click();
+        
+        // Act - switch back to details
+        IElement? detailsButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Merchant Details"));
+        detailsButton?.Click();
+        
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("Merchant Name"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_LoadMerchantData_LoadFails_NavigatesToError()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        this.MerchantUIService.Setup(m => m.GetMerchant(It.IsAny<CorrelationId>(), It.IsAny<Guid>(), merchantId))
+            .ReturnsAsync(Result.Failure());
+
+        // Act
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        
+        // Assert
+        cut.WaitForState(() => _fakeNavigationManager.Uri.Contains("error"), TimeSpan.FromSeconds(5));
+        _fakeNavigationManager.Uri.ShouldContain("error");
+    }
+
+    [Fact]
+    public void MerchantsEdit_DisplaysNoOperators_WhenNoneAssigned()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        SetupSuccessfulDataLoad(merchantId);
+        
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Act - Switch to operators tab
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? operatorsButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Assigned Operators"));
+        operatorsButton?.Click();
+        
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("No operators assigned"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_DisplaysNoContracts_WhenNoneAssigned()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        SetupSuccessfulDataLoad(merchantId);
+        
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Act - Switch to contracts tab
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? contractsButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Assigned Contracts"));
+        contractsButton?.Click();
+        
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("No contracts assigned"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_DisplaysNoDevices_WhenNoneAssigned()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        SetupSuccessfulDataLoad(merchantId);
+        
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Act - Switch to devices tab
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? devicesButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Assigned Devices"));
+        devicesButton?.Click();
+        
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("No devices assigned"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_AddOperatorButton_TogglesAddOperatorForm()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        SetupSuccessfulDataLoad(merchantId);
+        
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Switch to operators tab
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? operatorsButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Assigned Operators"));
+        operatorsButton?.Click();
+        
+        // Act - Click Add Operator button
+        IElement addOperatorButton = cut.Find("#addOperatorButton");
+        addOperatorButton.Click();
+        
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("Select Operator"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_AddContractButton_TogglesAddContractForm()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        SetupSuccessfulDataLoad(merchantId);
+        
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Switch to contracts tab
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? contractsButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Assigned Contracts"));
+        contractsButton?.Click();
+        
+        // Act - Click Add Contract button
+        IElement addContractButton = cut.Find("#addContractButton");
+        addContractButton.Click();
+        
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("Select Contract"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_AddDeviceButton_TogglesAddDeviceForm()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        SetupSuccessfulDataLoad(merchantId);
+        
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Switch to devices tab
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? devicesButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Assigned Devices"));
+        devicesButton?.Click();
+        
+        // Act - Click Add Device button
+        IElement addDeviceButton = cut.Find("#addDeviceButton");
+        addDeviceButton.Click();
+        
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("Device Identifier"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_AddOperator_Success_ShowsSuccessMessage()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        Guid operatorId = Guid.NewGuid();
+        OperatorModels.OperatorDropDownModel operatorToAdd = new() {
+            OperatorId = operatorId,
+            OperatorName = "Test Operator"
+        };
+        
+        SetupSuccessfulDataLoadWithOperators(merchantId, new List<OperatorModels.OperatorDropDownModel> { operatorToAdd });
+        
+        OperatorModels.OperatorModel operatorDetails = new() {
+            OperatorId = operatorId,
+            Name = "Test Operator",
+            RequireCustomMerchantNumber = false,
+            RequireCustomTerminalNumber = false
+        };
+        
+        this.OperatorUIService.Setup(o => o.GetOperator(It.IsAny<CorrelationId>(), It.IsAny<Guid>(), operatorId))
+            .ReturnsAsync(Result.Success(operatorDetails));
+        this.MerchantUIService.Setup(m => m.AddOperatorToMerchant(It.IsAny<CorrelationId>(), It.IsAny<Guid>(), merchantId, operatorId, It.IsAny<String?>(), It.IsAny<String?>()))
+            .ReturnsAsync(Result.Success);
+
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Switch to operators tab
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? operatorsButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Assigned Operators"));
+        operatorsButton?.Click();
+        
+        // Click Add Operator button
+        IElement addOperatorButton = cut.Find("#addOperatorButton");
+        addOperatorButton.Click();
+        
+        // Act - Select operator and add
+        IElement selectElement = cut.Find("select");
+        selectElement.Change(operatorId.ToString());
+        cut.WaitForState(() => cut.Markup.Contains("Add"), TimeSpan.FromSeconds(5));
+        
+        IElement addButton = cut.FindAll("button")
+            .First(b => b.TextContent.Trim() == "Add" && (b.GetAttribute("id") ?? "") != "addOperatorButton");
+        addButton.Click();
+
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("Operator added successfully"), timeout: TimeSpan.FromSeconds(10));
+    }
+
+    [Fact]
+    public void MerchantsEdit_AddOperator_Failure_ShowsErrorMessage()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        Guid operatorId = Guid.NewGuid();
+        OperatorModels.OperatorDropDownModel operatorToAdd = new() {
+            OperatorId = operatorId,
+            OperatorName = "Test Operator"
+        };
+        
+        SetupSuccessfulDataLoadWithOperators(merchantId, new List<OperatorModels.OperatorDropDownModel> { operatorToAdd });
+        
+        OperatorModels.OperatorModel operatorDetails = new() {
+            OperatorId = operatorId,
+            Name = "Test Operator",
+            RequireCustomMerchantNumber = false,
+            RequireCustomTerminalNumber = false
+        };
+        
+        this.OperatorUIService.Setup(o => o.GetOperator(It.IsAny<CorrelationId>(), It.IsAny<Guid>(), operatorId))
+            .ReturnsAsync(Result.Success(operatorDetails));
+        this.MerchantUIService.Setup(m => m.AddOperatorToMerchant(It.IsAny<CorrelationId>(), It.IsAny<Guid>(), merchantId, operatorId, It.IsAny<String?>(), It.IsAny<String?>()))
+            .ReturnsAsync(Result.Failure());
+
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Switch to operators tab
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? operatorsButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Assigned Operators"));
+        operatorsButton?.Click();
+        
+        // Click Add Operator button
+        IElement addOperatorButton = cut.Find("#addOperatorButton");
+        addOperatorButton.Click();
+        
+        // Act - Select operator and add
+        IElement selectElement = cut.Find("select");
+        selectElement.Change(operatorId.ToString());
+        cut.WaitForState(() => cut.Markup.Contains("Add"), TimeSpan.FromSeconds(5));
+        
+        IElement addButton = cut.FindAll("button")
+            .First(b => b.TextContent.Trim() == "Add" && (b.GetAttribute("id") ?? "") != "addOperatorButton");
+        addButton.Click();
+
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("Failed to add operator"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_RemoveOperator_Success_ShowsSuccessMessage()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        Guid operatorId = Guid.NewGuid();
+        MerchantModels.MerchantOperatorModel assignedOperator = new() {
+            OperatorId = operatorId,
+            OperatorName = "Test Operator"
+        };
+        
+        SetupSuccessfulDataLoadWithAssignedOperators(merchantId, new List<MerchantModels.MerchantOperatorModel> { assignedOperator });
+
+        this.MerchantUIService.Setup(m => m.RemoveOperatorFromMerchant(It.IsAny<CorrelationId>(), It.IsAny<Guid>(), merchantId, operatorId))
+            .ReturnsAsync(Result.Success);
+
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Switch to operators tab
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? operatorsButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Assigned Operators"));
+        operatorsButton?.Click();
+        
+        // Act - Remove operator
+        IRefreshableElementCollection<IElement> removeButtons = cut.FindAll("button");
+        IElement? removeButton = removeButtons.FirstOrDefault(b => b.TextContent.Contains("Remove"));
+        removeButton?.Click();
+        
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("Operator removed successfully"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_RemoveOperator_Failure_ShowsErrorMessage()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        Guid operatorId = Guid.NewGuid();
+        MerchantModels.MerchantOperatorModel assignedOperator = new() {
+            OperatorId = operatorId,
+            OperatorName = "Test Operator"
+        };
+        
+        SetupSuccessfulDataLoadWithAssignedOperators(merchantId, new List<MerchantModels.MerchantOperatorModel> { assignedOperator });
+
+        this.MerchantUIService.Setup(m => m.RemoveOperatorFromMerchant(It.IsAny<CorrelationId>(), It.IsAny<Guid>(), merchantId, operatorId))
+            .ReturnsAsync(Result.Failure(String.Empty));
+
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Switch to operators tab
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? operatorsButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Assigned Operators"));
+        operatorsButton?.Click();
+        
+        // Act - Remove operator
+        IRefreshableElementCollection<IElement> removeButtons = cut.FindAll("button");
+        IElement? removeButton = removeButtons.FirstOrDefault(b => b.TextContent.Contains("Remove"));
+        removeButton?.Click();
+        
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("Failed to remove operator"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_AssignContract_Success_ShowsSuccessMessage()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        Guid contractId = Guid.NewGuid();
+        ContractModels.ContractDropDownModel contractToAdd = new() {
+            ContractId = contractId,
+            Description = "Test Contract",
+            OperatorName = "Test Operator"
+        };
+        
+        SetupSuccessfulDataLoadWithContracts(merchantId, new List<ContractModels.ContractDropDownModel> { contractToAdd });
+
+        this.MerchantUIService.Setup(m => m.AssignContractToMerchant(It.IsAny<CorrelationId>(), It.IsAny<Guid>(), merchantId, contractId))
+            .ReturnsAsync(Result.Success);
+
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Switch to contracts tab
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? contractsButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Assigned Contracts"));
+        contractsButton?.Click();
+        
+        // Click Add Contract button
+        IElement addContractButton = cut.Find("#addContractButton");
+        addContractButton.Click();
+        
+        // Act - Select contract and assign
+        IElement selectElement = cut.Find("select");
+        selectElement.Change(contractId.ToString());
+        IElement assignButton = cut.FindAll("button")
+            .First(b => b.TextContent.Trim() == "Assign");
+        assignButton.Click();
+
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("Contract assigned successfully"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_AssignContract_Failure_ShowsErrorMessage()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        Guid contractId = Guid.NewGuid();
+        ContractModels.ContractDropDownModel contractToAdd = new() {
+            ContractId = contractId,
+            Description = "Test Contract",
+            OperatorName = "Test Operator"
+        };
+        
+        SetupSuccessfulDataLoadWithContracts(merchantId, new List<ContractModels.ContractDropDownModel> { contractToAdd });
+
+        this.MerchantUIService.Setup(m => m.AssignContractToMerchant(It.IsAny<CorrelationId>(), It.IsAny<Guid>(), merchantId, contractId))
+            .ReturnsAsync(Result.Failure());
+
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Switch to contracts tab
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? contractsButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Assigned Contracts"));
+        contractsButton?.Click();
+        
+        // Click Add Contract button
+        IElement addContractButton = cut.Find("#addContractButton");
+        addContractButton.Click();
+        
+        // Act - Select contract and assign
+        IElement selectElement = cut.Find("select");
+        selectElement.Change(contractId.ToString());
+        IElement assignButton = cut.FindAll("button")
+            .First(b => b.TextContent.Trim() == "Assign");
+        assignButton.Click();
+
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("Failed to assign contract"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_RemoveContract_Success_ShowsSuccessMessage()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        Guid contractId = Guid.NewGuid();
+        MerchantModels.MerchantContractModel assignedContract = new() {
+            ContractId = contractId,
+            ContractName = "Test Contract",
+            OperatorName = "Test Operator"
+        };
+        
+        SetupSuccessfulDataLoadWithAssignedContracts(merchantId, new List<MerchantModels.MerchantContractModel> { assignedContract });
+
+        this.MerchantUIService.Setup(m => m.RemoveContractFromMerchant(It.IsAny<CorrelationId>(), It.IsAny<Guid>(), merchantId, contractId))
+            .ReturnsAsync(Result.Success);
+
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Switch to contracts tab
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? contractsButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Assigned Contracts"));
+        contractsButton?.Click();
+        
+        // Act - Remove contract
+        IRefreshableElementCollection<IElement> removeButtons = cut.FindAll("button");
+        IElement? removeButton = removeButtons.FirstOrDefault(b => b.TextContent.Contains("Remove"));
+        removeButton?.Click();
+        
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("Contract removed successfully"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_RemoveContract_Failure_ShowsErrorMessage()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        Guid contractId = Guid.NewGuid();
+        MerchantModels.MerchantContractModel assignedContract = new() {
+            ContractId = contractId,
+            ContractName = "Test Contract",
+            OperatorName = "Test Operator"
+        };
+        
+        SetupSuccessfulDataLoadWithAssignedContracts(merchantId, new List<MerchantModels.MerchantContractModel> { assignedContract });
+
+        this.MerchantUIService.Setup(m => m.RemoveContractFromMerchant(It.IsAny<CorrelationId>(), It.IsAny<Guid>(), merchantId, contractId))
+            .ReturnsAsync(Result.Failure(String.Empty));
+
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Switch to contracts tab
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? contractsButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Assigned Contracts"));
+        contractsButton?.Click();
+        
+        // Act - Remove contract
+        IRefreshableElementCollection<IElement> removeButtons = cut.FindAll("button");
+        IElement? removeButton = removeButtons.FirstOrDefault(b => b.TextContent.Contains("Remove"));
+        removeButton?.Click();
+        
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("Failed to remove contract"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_DisplaysAssignedOperators_WhenPresent()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        Guid operatorId = Guid.NewGuid();
+        MerchantModels.MerchantOperatorModel assignedOperator = new() {
+            OperatorId = operatorId,
+            OperatorName = "Test Operator"
+        };
+        
+        SetupSuccessfulDataLoadWithAssignedOperators(merchantId, new List<MerchantModels.MerchantOperatorModel> { assignedOperator });
+
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Act - Switch to operators tab
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? operatorsButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Assigned Operators"));
+        operatorsButton?.Click();
+        
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("Test Operator"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    [Fact]
+    public void MerchantsEdit_DisplaysAssignedContracts_WhenPresent()
+    {
+        // Arrange
+        var merchantId = Guid.NewGuid();
+        Guid contractId = Guid.NewGuid();
+        MerchantModels.MerchantContractModel assignedContract = new() {
+            ContractId = contractId,
+            ContractName = "Test Contract",
+            OperatorName = "Test Operator"
+        };
+        
+        SetupSuccessfulDataLoadWithAssignedContracts(merchantId, new List<MerchantModels.MerchantContractModel> { assignedContract });
+
+        IRenderedComponent<MerchantsEdit> cut = RenderComponent<MerchantsEdit>(parameters => parameters
+            .Add(p => p.MerchantId, merchantId));
+        cut.WaitForState(() => !cut.Markup.Contains("animate-spin"), TimeSpan.FromSeconds(5));
+        
+        // Act - Switch to contracts tab
+        IRefreshableElementCollection<IElement> buttons = cut.FindAll("button");
+        IElement? contractsButton = buttons.FirstOrDefault(b => b.TextContent.Contains("Assigned Contracts"));
+        contractsButton?.Click();
+        
+        // Assert
+        cut.WaitForAssertion(() => cut.Markup.ShouldContain("Test Contract"), timeout: TimeSpan.FromSeconds(5));
+    }
+
+    // Helper methods
+    private void SetupSuccessfulDataLoad(Guid merchantId, 
+                                         string merchantName = "Test Merchant", 
+                                         string merchantReference = "MERCH001",
+                                         List<MerchantModels.MerchantOperatorModel>? assignedOperators = null,
+                                         List<OperatorModels.OperatorDropDownModel>? availableOperators = null,
+                                         List<MerchantModels.MerchantContractModel>? assignedContracts = null,
+                                         List<ContractModels.ContractDropDownModel>? availableContracts = null,
+                                         List<MerchantModels.MerchantDeviceModel>? assignedDevices = null)
+    {
+        MerchantModels.MerchantModel merchant = new() {
+            MerchantId = merchantId,
+            MerchantName = merchantName,
+            MerchantReference = merchantReference,
+            AddressId = Guid.NewGuid(),
+            AddressLine1 = "123 Test St",
+            AddressLine2 = "Suite 100",
+            Town = "Test Town",
+            Region = "Test Region",
+            PostalCode = "12345",
+            Country = "GB",
+            ContactId = Guid.NewGuid(),
+            ContactName = "Test Contact",
+            ContactEmailAddress = "test@example.com",
+            ContactPhoneNumber = "1234567890",
+            SettlementSchedule = "Immediate",
+            Balance = 1000.00m,
+            AvailableBalance = 500.00m
+        };
+        
+        this.MerchantUIService.Setup(m => m.GetMerchant(It.IsAny<CorrelationId>(), It.IsAny<Guid>(), merchantId))
+            .ReturnsAsync(Result.Success(merchant));
+        
+        this.MerchantUIService.Setup(m => m.GetMerchantOperators(It.IsAny<CorrelationId>(), It.IsAny<Guid>(), merchantId))
+            .ReturnsAsync(Result.Success(assignedOperators ?? new List<MerchantModels.MerchantOperatorModel>()));
+        
+        this.MerchantUIService.Setup(m => m.GetMerchantContracts(It.IsAny<CorrelationId>(), It.IsAny<Guid>(), merchantId))
+            .ReturnsAsync(Result.Success(assignedContracts ?? new List<MerchantModels.MerchantContractModel>()));
+        
+        this.MerchantUIService.Setup(m => m.GetMerchantDevices(It.IsAny<CorrelationId>(), It.IsAny<Guid>(), merchantId))
+            .ReturnsAsync(Result.Success(assignedDevices ?? new List<MerchantModels.MerchantDeviceModel>()));
+        
+        this.OperatorUIService.Setup(o => o.GetOperatorsForDropDown(It.IsAny<CorrelationId>(), It.IsAny<Guid>()))
+            .ReturnsAsync(Result.Success(availableOperators ?? new List<OperatorModels.OperatorDropDownModel>()));
+        
+        this.ContractUIService.Setup(c => c.GetContractsForDropDown(It.IsAny<CorrelationId>(), It.IsAny<Guid>()))
+            .ReturnsAsync(Result.Success(availableContracts ?? new List<ContractModels.ContractDropDownModel>()));
+    }
+
+    private void SetupSuccessfulDataLoadWithOperators(Guid merchantId, List<OperatorModels.OperatorDropDownModel> operators)
+        => SetupSuccessfulDataLoad(merchantId, availableOperators: operators);
+
+    private void SetupSuccessfulDataLoadWithAssignedOperators(Guid merchantId, List<MerchantModels.MerchantOperatorModel> assignedOperators)
+        => SetupSuccessfulDataLoad(merchantId, assignedOperators: assignedOperators);
+
+    private void SetupSuccessfulDataLoadWithContracts(Guid merchantId, List<ContractModels.ContractDropDownModel> contracts)
+        => SetupSuccessfulDataLoad(merchantId, availableContracts: contracts);
+
+    private void SetupSuccessfulDataLoadWithAssignedContracts(Guid merchantId, List<MerchantModels.MerchantContractModel> assignedContracts)
+        => SetupSuccessfulDataLoad(merchantId, assignedContracts: assignedContracts);
+}
diff --git a/EstateManagementUI.BlazorServer/Components/Pages/Merchants/Edit.razor.cs b/EstateManagementUI.BlazorServer/Components/Pages/Merchants/Edit.razor.cs
index c47b3e28..d597f5c2 100644
--- a/EstateManagementUI.BlazorServer/Components/Pages/Merchants/Edit.razor.cs
+++ b/EstateManagementUI.BlazorServer/Components/Pages/Merchants/Edit.razor.cs
@@ -20,9 +20,6 @@ public partial class Edit {
         private MerchantModels.MerchantModel? merchant;
         private bool isLoading = true;
         private bool isSaving = false;
-        private string? errorMessage;
-        private string? successMessage;
-        private string activeTab = "details";
 
         // Unified model for editing
         private MerchantModels.MerchantEditModel merchantEditModel = new();
@@ -49,6 +46,11 @@ public partial class Edit {
         private bool showAddDevice = false;
         private string? deviceIdentifier;
 
+        protected override async Task OnInitializedAsync() {
+            await base.OnInitializedAsync();
+            this.SetActiveTab("details");
+        }
+
         protected override async Task OnAfterRenderAsync(bool firstRender) {
             if (!firstRender) {
                 return;