Testing code in sharepoint context

Scenario:
You want to test the webpart code in sharepoint context
Solution:
You can use the Visual Studio Test classes. Code sample shows both using Context and without context.

Code(Without Context):

public static string GetSiteTitle(string url) { 
    SPSite site = new SPSite(url); 
    string title = site.RootWeb.Title; 
    site.RootWeb.Dispose(); 
    site.Dispose(); 
    return title; 
} 

[TestMethod()] 
public void GetSiteTitleTest() { 
  string url = http://localhost; 
  string expected = "Home"; 
  string actual = MyClass.GetSiteTitle(url); 
  Assert.AreEqual(expected, actual); 
}

Code(With Context):

public static string GetSiteTitle() { 
    SPSite site = SPContext.Current.Site; 
    string title = site.RootWeb.Title; 
    return title; 
}

[TestMethod()] 
[HostType("ASP.Net")] 
[UrlToTest("http://localhost/default.aspx")] 
public void GetSiteTitleTest() { 
  string expected = "Home";  
  string  actual = MyClassName.GetSiteTitle(); 
  Assert.AreEqual(expected, actual); 
}

Article:
http://blogs.msdn.com/mcsnoiwb/archive/2008/10/08/unit-testing-sharepoint-code.aspx