public void Add_Does_Not_Accept_Null()
{
var servicesMock = new Mock <IServiceCollection>().Object;
var providerMock = new Mock <IServiceProvider>().Object;
var containerMock = new DIContainer(servicesMock, providerMock);
var error = Assert.Throws <ArgumentNullException>(() => containerMock.Add(null));
Assert.Equal("serviceType", error.ParamName);
}