unit test

Question

when i test my form using unit test at that time i got an error 
that is shown below

public void button2_ClickTest()

        {

            Form1_Accessor target = new Form1_Accessor(); // TODO: Initialize to an appropriate value

            object sender = null; // TODO: Initialize to an appropriate value

            EventArgs e = null; // TODO: Initialize to an appropriate value

            target.button2_Click(sender, e);

            Assert.Inconclusive("A method that does not return a value cannot be verified.");

        }

errror in target.button2_Click(sender, e); line 
how can clear it?