def test_rels_pn
    assert_equal(@ws.rels_pn, "worksheets/_rels/sheet1.xml.rels")
    ws = @ws.workbook.add_worksheet
    assert_equal(ws.rels_pn, "worksheets/_rels/sheet2.xml.rels")
  end
def test_use_gridlines
assert_raise(ArgumentError) { @ws.show_gridlines = -1.1 }
assert_nothing_raised { @ws.show_gridlines = false }
assert_equal(@ws.show_gridlines, false)
end
def test_selected
assert_raise(ArgumentError) { @ws.selected = -1.1 }
assert_nothing_raised { @ws.selected = true }
assert_equal(@ws.selected, true)
end