Please find my service class

using NotificationJob.Service.Email.SendGrid;
using NotificationJob.Service.Email.Settings;
using Microsoft.Extensions.Options;
using SendGrid;
using SendGrid.Helpers.Mail;
using Response = SendGrid.Response;

namespace NotificationJob.Service;

public class EmailService(
        IOptions<Settings> emailAlertSettings,
        ILogger<EmailService> logger
        )  : IEmailService
{
    private readonly Settings emailAlertSettings = emailAlertSettings.Value;
    private ILogger<EmailService> _logger { get; } = logger;
    public async Task<Response> SendEmail(string to, string subject, string body, string displayName, bool isSandbox=false)
    {
        var apiKey = emailAlertSettings.SendGridKey;
        var eNotificationSenderEmailId = emailAlertSettings.ENotificationSenderEmailId;
        var client = new SendGridClient(apiKey);

        SendGridMessage sendMail = new SendGridMessage();
        sendMail.From = new EmailAddress(eNotificationSenderEmailId);
        sendMail.Subject = subject;
        sendMail.AddTo(new EmailAddress(to, displayName));


        string result = string.Empty;
        //Enable Sandbox for testing based on config value
        if (isSandbox)
        {
            sendMail.SetSandBoxMode(true);
        }
        try
        {
            sendMail.HtmlContent = body;
            var response = await client.SendEmailAsync(sendMail);
            _logger.LogInformation($"Email sent {to} subject {subject} displayName {displayName} @{DateTime.UtcNow}: with status code: {response.IsSuccessStatusCode}");
            return response;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, $"Error sending email  to {to} subject {subject} displayName {displayName} @{DateTime.UtcNow}: {ex.Message}");
            throw;
        } 
    }
}

Pease find the unit test

public class EmailServiceTests
{
    private Mock<IOptions<Settings>> _mockSettings;
    private Mock<ILogger<EmailService>> _mockLogger;
    private EmailService _emailService;

    public EmailServiceTests()
    {
        _mockSettings = new Mock<IOptions<Settings>>();
        _mockLogger = new Mock<ILogger<EmailService>>();
    }

    [Fact]
    public async Task SendEmail_Success_LogsAndReturnsResponse()
    {
        // Arrange
        var to = "[email protected]";
        var subject = "Test Email";
        var body = "This is a test email body.";
        var displayName = "Test User";
        var apiKey = "your_api_key"; // Replace with actual API key
        var senderEmailId = "[email protected]";

        _mockSettings.Setup(s => s.Value.SendGridKey).Returns(apiKey);
        _mockSettings.Setup(s => s.Value.ENotificationSenderEmailId).Returns(senderEmailId);

        var mockResponse = new Mock<Response>();
        mockResponse.Setup(r => r.IsSuccessStatusCode).Returns(true);

        var mockClient = new Mock<SendGridClient>(apiKey);
        mockClient.Setup(c => c.SendEmailAsync(It.IsAny<SendGridMessage>()))
            .Returns(Task.FromResult(mockResponse.Object));

        _emailService = new EmailService(_mockSettings.Object, _mockLogger.Object);

        // Act
        var response = await _emailService.SendEmail(to, subject, body, displayName);

        // Assert
        mockClient.Verify(c => c.SendEmailAsync(It.IsAny<SendGridMessage>()), Times.Once);
        _mockLogger.Verify(l => l.LogInformation(
            It.Is<string>(s => s.Contains(subject) && s.Contains(displayName))), Times.Once);
        Assert.NotNull(response);
        Assert.True(response.IsSuccessStatusCode);
    }

}

The problem is getting error in mockResponse.Setup(r => r.IsSuccessStatusCode).Returns(true); as

System.NotSupportedException : Unsupported expression: r => r.IsSuccessStatusCode
Non-overridable members (here: Response.get_IsSuccessStatusCode) may not be used in setup / verification expressions.

Please advise how can i setup mock Response