Many people seem to have a hard time finding a good procedure to migrate unit test from nUnit to VSTS so I thought I'd post the way I'd make the conversion.
Jim Newkirk has created a conversion tool that's available at http://www.gotdotnet.com/workspaces/workspace.aspx?id=91936c5e-461f-4027-bdba-8a46f52fefdb.
Personally I prefer to do the conversion by hand (not a lot of work anyway). Here's also a step-by-step guide for manually converting nUnit tests to a VSTS unit test project:
1. Add a reference to Microsoft.VisualStudio.QualityTools.UnitTestFramework.
2. Remove reference to nunit.framework.
3. Change the following namespace imports:
C#: Change using NUnit.Framework declaratives to using Microsoft.VisualStudio.TestTools.UnitTesting
VB: Change Imports NUnit.Framework declaratives to Imports Microsoft.VisualStudio.TestTools.UnitTesting
4. Search and replace the following:
C#: [TestFixture] => [TestClass]
VB: <TestFixture()> => <TestClass()>
C#: [TestFixtureSetUp] => [ClassInitialize]
VB: <TestFixtureSetUp()> => <ClassInitialize()>
C#: [TestFixtureTearDown] => [ClassCleanup]
VB: <TestFixtureTearDown()> => <ClassCleanup()>
C#: [SetUp] => [TestInitialize]
VB: <SetUp()> => <TestInitialize()>
C#: [TearDown] => [TestCleanup]
VB: <TearDown()> => <TestCleanup()>
C#: [Test] => [TestMethod]
VB: <Test()> => <TestMethod()>
Assert.Ignore => Assert.Inconclusive
5. Open the Visual Studio project file in Xml (using Open As... in Visual Studio or use Notepad) and add the following to the msbuild script:
Paste the following line in the <PropertyGroup> that contains <AssemblyName> and other properties:
C#: <ProjectTypeGuids>{3AC096D0-A1C2-E12C-1390-A8335801FDAB};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
VB: <ProjectTypeGuids>{3AC096D0-A1C2-E12C-1390-A8335801FDAB};{F184B08F-C81C-45F6-A57F-5ABD9991F28F}</ProjectTypeGuids>