A quick and dirty way to distinguish between the test environment and the live environment:

    If HttpContext.Current Is Nothing Then

It may be that the REASON your Trace.Write statements are throwing the NullReferenceException is because Trace is relying on there being an HttpContext. If so, you could mock the HttpContext:

    <TestInitialize()>
    Public Sub Setup()
        'Since this is not a real web app, we need to mock at least
        'the current HttpContext
        HttpContext.Current = New HttpContext( _
            New HttpRequest("", "http://tempuri.org", ""), _
            New HttpResponse(New StringWriter()) _
        )
    End Sub

I'm trying to add some unit tests to some legacy code.  Many of the functions begin with `Trace.Write`



    Function FormatDate(ByVal inputAsString As String) As String
        Trace.Write("Function FormatDate")

When I run Tests against the full set of ASP.NET Unit test attributes, it takes too long:



    <TestMethod(), _ 
    HostType("ASP.NET"), _ 
    UrlToTest("http://localhost:25153/WebSite1"), _
    AspNetDevelopmentServerHost("C:\WebSite1", "/WebSite1")>
    Public Sub FormatDateTest()

In response, I've just been testing an instance of the class itself:



    <TestMethod(), _ 
    Public Sub FormatDateTest()

This works quickly, but I get an "Object Reference No Set to an instance of an Object" error when I arrive at `Trace.Write()`

Is there some way I can test if I'm running unit tests and not call trace?  Can I mock an html object so that it doesn't throw an excpetion?  Can I push right past the exception? Should I just get rid of Trace?  I'd kind of like to keep the tests within MsTest since I'm in a pretty strictly Microsoft derivitive product shop.

**Update**

Here's the stacktrace from the `NullReferenceException`

    at System.Web.UI.UserControl.get_Trace()
    at Applications.Interface.UCparent.FormatDate(String inputAsString, Boolean isFuzzy, Char& precision) 
    in \\...\UCparent.ascx.vb:line 285

The `Trace.Write` method returns the `System.Web.TraceContext` of the Page on which it is called. Essentially, it is idential to writing `Page.Trace.Write`

The problem is, when using @[Ross Presser](https://stackoverflow.com/users/864696/ross-presser)'s suggestion of adding `HttpContext.Current` to the Unit Test Setup, it's still the case that `Page.Trace Is Nothing = True`



    'This Works
    HttpContext.Current.Trace.Write("HttpContext.Current")
    'This Doesn't
    Page.Trace.Write("Page.TraceContext")
    'This Doesn't
    Trace.Write("Page.TraceContext")

I can go in and change all the Trace.Write methods to use the HttpContext intstead of the default page context, but that runs into the same problem as earlier.  Also the `Trace` property on `Page` has no setter, so it seems difficult to just give the page some context without it naturally inheriting it.

Unit Testing methods with Trace.Write() in ASP.NET with MSTest

1. Open up **`Local.testsettings`** in your Solution Explorer > Solution Items  
   ![local.testSettings](http://i.imgur.com/UNxWOIz.png)

2. Go to Deployment and make sure **`Enabled Deployment`** is checked 
   <sup>(it's unchecked by default)</sup>  
   ![Enabled Deployment](http://i.imgur.com/VtfoiwF.png)

In Visual Studio 2010 when I create the default test project with the following bare bones code:



    <TestClass()>
    Public Class UnitTest1
    
        <TestMethod()>
        Public Sub TestMethod1()

            Assert.AreEqual(1, 1)
    
        End Sub
    
    End Class

I get the following error:

> Unit Test Adapter threw exception:   
URI formats are not supported..  
-- Exception doesn't have a stack trace -- 

![screenshot](http://i.imgur.com/koK2Uds.png)

Unit Test Adapter threw exception: URI formats are not supported

Adapted Jon Davis's answer on [Unit Testing ASP.NET DataAnnotations validation][1]

If you have a class like this:

```cs
public class Person
{
  [MinLength(3, ErrorMessage = "FIRSTNAME_LENGTH_MIN")]
  public string FirstName { get; set; }

  [MinLength(3, ErrorMessage = "MOBILENUMBER_LENGTH_MIN")]
  public string MobileNumber { get; set; }
}
```

You can test the validation results like this:


```cs
[TestMethod]
public void ModelValidationFailsWithInvalidLength()
{
  // arrange
  var myPerson = new Person()
  {
    FirstName = "Hi",
    MobileNumber = "12"
  };

  // act
  var validationResults = ValidateModel(myPerson);

  // assert
  Assert.IsTrue(validationResults.Any(
    v => v.MemberNames.Contains(nameof(Person.FirstName)) &&
         v.ErrorMessage.Contains("FIRSTNAME_LENGTH_MIN")));
}

private IList<ValidationResult> ValidateModel(object model)
{
  var validationResults = new List<ValidationResult>();
  var ctx = new ValidationContext(model, null, null);
  Validator.TryValidateObject(model, ctx, validationResults, true);
  return validationResults;
}
```


[1]: https://stackoverflow.com/a/4331964/1366033

I was trying to do unit testing for validations on c# models using Validator but it is not working with NewtonSoft attributes. 

Here's my unit test:


```cs
var searchController = new SearchController();
var requestModel = new RequestModel
{
   Id = "23456",
   MobileNumber = "9876543210"
};

var results = new List<ValidationResult>();
var context = new ValidationContext(requestModel, null, null);
var isvalid = Validator.TryValidateObject(requestModel, context, results,true);
Assert.IsFalse(isvalid);
```


And here's my model:

```cs
public class XYZ
{
    [JsonProperty("mobileNumber")]
    [MinLength(3, ErrorMessage = "MOBILENUMBER_LENGTH_MIN")]
    public string MobileNumber { get; set; }

    [JsonProperty("refNumber")]
    [MinLength(3, ErrorMessage = "REFNUMBER_LENGTH_MIN")]
    public string RefNumber { get; set; }

    [JsonProperty("subscriberFirstName")]
    [MinLength(3, ErrorMessage = "FIRSTNAME_LENGTH_MIN")]
    public string FirstName { get; set; }
}
```

Can someone help me with this?