How to write unit test for method in back of windows form code

Invoke or BeginInvoke cannot be called on a control until the window handle has been created.

public partial class ImportForm : Form{
 public ImportForm()
        {
        }
  public bool Test(string[] fileNames)//Method to test
        {
          return true;
        }
}

[TestMethod]
public void TestTest()
{


    bool results=false;
    var files = new string[4];
    files[0] = @"filename1.xlsx";
    files[1] = @"filename2.xlsx";

    ImportForm form= new ImportForm();
     results = form.Test(files);

    Assert.AreEqual(true, results);
}