[TestMethod]
        public void TestCast()
        {
            Mock<VBProject> vbProject = new Mock<VBProject>();
            vbProject.Setup(x => x.Name).Returns("projectName");
            vbProject.Setup(x => x.Protection).Returns(vbext_ProjectProtection.vbext_pp_none);

            var projectList = new VBProject[] {vbProject.Object, vbProject.Object};
            // here is my workaround
            VBProjects vbProjects = new VbProjectFake(projectList);

            Mock<VBE> vbe = new Mock<VBE>();

 public class VbProjectFake : VBProjects
    {

        private IEnumerable<VBProject> _projects;

        public VbProjectFake(IEnumerable<VBProject> projects )
        {
            _projects = projects;
        }

        public VBProject Add(vbext_ProjectType Type)
        {
            throw new NotImplementedException();
        }

        public int Count
        {
            get { return _projects.ToList().Count; }
        }

        public System.Collections.IEnumerator GetEnumerator()

    var projectList = new List<VBProject>() { mockProject1, mockProject2 };

    var projects = new Mock<VBProjects>();
    projects.Setup(p => p.GetEnumerator()).Returns(projectList.GetEnumerator());