VS

PM>  Install-Package Unity

Web.config

<configSections>
<section name="unity" type="Microsoft.Practices.Unity.Configuration.UnityConfigurationSection,Microsoft.Practices.Unity.Configuration" />
</configSections>

    <unity xmlns="http://schemas.microsoft.com/practices/2010/unity">
    <container>    
        <register type="Common.Interfaces.IGetTestBLL,Common" mapTo="R365.Common.BusinessLogic.GetDummyTestBLL,Common" />
      </container>
  </unity>

 UnityHelper.cs

using Microsoft.Practices.Unity;

namespace VML.Employee.Common.Utils
{
    public static class UnityHelper
    {
        private static IUnityContainer unityContainer = new UnityContainer();

        static UnityHelper()
        {

        }

        public static IUnityContainer UnityContainer
        {
            get
            {
                return unityContainer;
            }
            set
            {
                unityContainer = value;
            }
        }

        public static T Resolve<T>(params ResolverOverride[] overrides)
        {
            return unityContainer.Resolve<T>(overrides);
        }

        public static T Resolve<T>(string name, params ResolverOverride[] overrides)
        {
            return unityContainer.Resolve<T>(name, overrides);
        }
    }
}

 IGetTestBLL.cs

    public interface IGetTestBLL
    {

        List<Test> GetTestById(int id);
    
    }

 GetTestBLL.cs

   // get dummpy data
    public class GetDummyTestBLL : IGetTestBLL 
    {

        public List<Test> GetTestById(int id)        {
            ...
        }
    }

    // get  data  from WebService
    public class GetWCFTestBLL : IGetTestBLL
    {

        public List<Test> GetTestById(int id)        {
            ...
        }
     }

UnityHelper.UnityContainer.LoadConfiguration();
IGetTestBLL getTest = UnityHelper.Resolve<IGetTestBLL>();
getTest.GetTestById(1);