Add unit tests for MerchantRequestHandler to achieve ~100% coverage

[Copilot]

MerchantRequestHandler had no unit test coverage. This PR adds 38 tests covering all 17 handler methods.

Coverage

• 8 queries: GetMerchants, GetMerchant, GetRecentMerchants, GetMerchantKpi, GetMerchantsForDropDown, GetMerchantContracts, GetMerchantOperators, GetMerchantDevices — success + failure per method
• 8 commands: AddMerchantDevice, AddOperatorToMerchant, CreateMerchant, MakeMerchantDeposit, RemoveContractFromMerchant, RemoveOperatorFromMerchant, SwapMerchantDevice, AssignContractToMerchant — success + failure per method
• UpdateMerchantCommand: 4 cases covering the sequential call chain — full success, and early-exit failure at each of UpdateMerchant, UpdateMerchantAddress, and UpdateMerchantContact

[Fact]
public async Task Handle_UpdateMerchantCommand_ReturnsFailure_WhenUpdateMerchantAddressFails()
{
    // UpdateMerchant succeeds, UpdateMerchantAddress fails → contact call never made
    _mockApiClient.Setup(c => c.UpdateMerchant(command, It.IsAny<CancellationToken>()))
        .ReturnsAsync(Result.Success());
    _mockApiClient.Setup(c => c.UpdateMerchantAddress(command, It.IsAny<CancellationToken>()))
        .ReturnsAsync(Result.Failure("update address failed"));

    var result = await _handler.Handle(command, CancellationToken.None);

    result.IsFailed.ShouldBeTrue();
    _mockApiClient.Verify(c => c.UpdateMerchantContact(command, It.IsAny<CancellationToken>()), Times.Never);
}

Tests follow the existing DateRequestHandlerTests conventions (Moq + Shouldly).

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• f.feedz.io
  • Triggering command: /usr/bin/dotnet dotnet test EstateManagementUI.BlazorServer.Tests/EstateManagementUI.BlazorServer.Tests.csproj --filter FullyQualifiedName~MerchantRequestHandlerTests (dns block)
  • Triggering command: /opt/hostedtoolcache/CodeQL/2.24.0/x64/codeql/csharp/tools/linux64/Semmle.Autobuild.CSharp /opt/hostedtoolcache/CodeQL/2.24.0/x64/codeql/csharp/tools/linux64/Semmle.Autobuild.CSharp (dns block)
  • Triggering command: /usr/bin/dotnet dotnet restore --no-dependencies /home/REDACTED/work/EstateManagementUI/EstateManagementUI/EstateManagementUI.sln --packages /home/REDACTED/work/EstateManagementUI/.codeql-scratch/dbs/csharp/working/packages /p:DisableImplicitNuGetFallbackFolder=true --verbosity normal /p:TargetFrameworkRootPath=/home/REDACTED/work/EstateManagementUI/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:NetCoreTargetingPackRoot=/home/REDACTED/work/EstateManagementUI/.codeql-scratch/dbs/csharp/working/emptyFakeDotnetRoot /p:AllowMissingPrunePackageData=true (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>MerchantRequestHandler Unit Tests</issue_title>
<issue_description>Ensure a good level of code coverage as close to 100% as possible</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes MerchantRequestHandler Unit Tests #783

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.