public class Model
{
    public int Id {get;set;}
    public string Name {get; set;}

    public void myAction(MyDatabase db, string r, string i) {
        db.DataEmp.Add(new DataEmp{
            Id = this.Id,
            DateOfAction = DateTime.UtcNow,
            R = r,
            I = i
        });
        db.SaveChanges();
    }
}

[Test]
    public void Method_Test_Pass_myAction()
    {
        newModel.myAction(db,"R","I");

        Assert.That(db.DataEmp.FirstOrDefault(de => de.Id == newModel.Id), Is.Null);
    }