testSetTextMultipleLines() {
    select(textarea);
    assertEquals('', selection.getText(textarea));
    const message = 'Get Behind Me\nSatan';
    selection.setText(textarea, message);
    assertEquals(message, selection.getText(textarea));

    // Select the text up to the point just after the \r\n combination
    // or \n in GECKO.
    const endOfNewline = 14;
    let selectedMessage = message.substring(0, endOfNewline);
    selection.setStart(textarea, 0);
    selection.setEnd(textarea, endOfNewline);
    assertEquals(selectedMessage, selection.getText(textarea));

    selectedMessage = '\n';
    selection.setStart(textarea, 13);
    selection.setEnd(textarea, endOfNewline);
    assertEquals(selectedMessage, selection.getText(textarea));
  }
Tests the setText routine for textarea with multiple lines of text.