I am using NUnit, and C# .NET 6. I am Mocking the service to return some data. However the service is always returning null in the Controller while executing the test case.

Service Method:

public async Task<Result<TResponseModel>> InvokeGenericService<TRequestModel, TResponseModel, 
TRequestEntity, TResponseEntity>(ControllerContext controllerContext, TRequestModel 
requestModel, AccountIndexModel cache, string pApiNameInConfig, CacheFilterParams 
cacheFilterParams = null)
where TResponseModel : class, new()
where TRequestEntity : class, new()
where TResponseEntity : class, new()
{
    //code.... 
}

Controller:

public async Task<IActionResult> UpdatePayment(AccountIndexModel cache, string 
accountIndex, [FromBody] UpdatePaymentRequestModel model)
{
    var response = await 
    genericService.InvokeGenericService<UpdatePaymentRequestModel, 
    UpdatePaymentResponseModel, UpdatePaymentRequestEntity, 
    UpdatePaymentResponseEntity>(ControllerContext, model, cache, 
    "UpdateReceiptsPayment", new CacheFilterParams { AccountIndex = accountIndex 
    });

    if (response.HasErrors) // response is always Null, despite mocking
    {
     // Other code        
    }
}

Test:

[Test]
public void  InvokeUpdatePayment_WithValidRequest_ReturnsSuccessResponse()
{
    this._mockIgenericService.Setup(service => 
    service.InvokeGenericService<UpdatePaymentRequestModel, UpdatePaymentResponseModel, 
    UpdatePaymentRequestEntity, UpdatePaymentResponseEntity> 
    (this.controllerContext.Object, It.IsAny<UpdatePaymentRequestModel>(), 
    It.IsAny<AccountIndexModel>(), "UpdateReceiptsPayment", It.IsAny<CacheFilterParams> 
    ()))
    .Returns(Task.FromResult(new Models.Result<UpdatePaymentResponseModel>
    {
        ResultData = GenerateStub.GetValidUpdatePaymentResponse(),
        ErrorList = null,
    }));

    var model = GenerateStub.GetValidUpdatePaymentRequestModel();

    var okResult = this._receiptsPaymentsController.UpdatePayment(
    GenerateStub.GetValidAccountIndexModel(), "2", model).GetAwaiter().GetResult() as 
    OkObjectResult; // It invokes Controller action method

    Assert.IsNotNull(okResult);
    
}