function test_initial_state()
  io.write('\ntest_initial_state')
  App.screen.init{width=120, height=60}
  Lines = load_array{}
  App.draw()
  check_eq(#Lines, 1, 'F - test_initial_state/#lines')
  check_eq(Cursor1.line, 1, 'F - test_initial_state/cursor:line')
  check_eq(Cursor1.pos, 1, 'F - test_initial_state/cursor:pos')
  check_eq(Screen_top1.line, 1, 'F - test_initial_state/screen_top:line')
  check_eq(Screen_top1.pos, 1, 'F - test_initial_state/screen_top:pos')
end
function test_click_to_create_drawing()
  io.write('\ntest_click_to_create_drawing')
  App.screen.init{width=120, height=60}
  Lines = load_array{}
  App.draw()
  App.run_after_mouse_click(8,Margin_top+8, 1)
  -- cursor skips drawing to always remain on text
  check_eq(#Lines, 2, 'F - test_click_to_create_drawing/#lines')
  check_eq(Cursor1.line, 2, 'F - test_click_to_create_drawing/cursor')
end
function test_backspace_to_delete_drawing()
  io.write('\ntest_backspace_to_delete_drawing')
  -- display a drawing followed by a line of text (you shouldn't ever have a drawing right at the end)
  App.screen.init{width=120, height=60}
  Lines = load_array{'```lines', '```', ''}
  -- cursor is on text as always (outside tests this will get initialized correctly)
  Cursor1.line = 2
  -- backspacing deletes the drawing
  App.run_after_keychord('backspace')
  check_eq(#Lines, 1, 'F - test_backspace_to_delete_drawing/#lines')
  check_eq(Cursor1.line, 1, 'F - test_backspace_to_delete_drawing/cursor')
end

end
function test_insert_newline_at_start_of_line()
  io.write('\ntest_insert_newline_at_start_of_line')
  -- display a line
  App.screen.init{width=25+30, height=60}
  Lines = load_array{'abc'}
  Line_width = App.screen.width
  Cursor1 = {line=1, pos=1}
  Screen_top1 = {line=1, pos=1}
  Screen_bottom1 = {}
  -- hitting the enter key splits the line
  App.run_after_keychord('return')
  check_eq(Cursor1.line, 2, 'F - test_insert_newline_at_start_of_line/cursor:line')
  check_eq(Cursor1.pos, 1, 'F - test_insert_newline_at_start_of_line/cursor:pos')
  check_eq(Lines[1].data, '', 'F - test_insert_newline_at_start_of_line/data:1')
  check_eq(Lines[2].data, 'abc', 'F - test_insert_newline_at_start_of_line/data:2')

end
function test_backspace_past_line_boundary()
  io.write('\ntest_backspace_past_line_boundary')
  -- position cursor at start of a (non-first) line
  App.screen.init{width=25+30, height=60}
  Lines = load_array{'abc', 'def'}
  Line_width = App.screen.width
  Cursor1 = {line=2, pos=1}
  -- backspace joins with previous line
  App.run_after_keychord('backspace')
  check_eq(Lines[1].data, 'abcdef', "F - test_backspace_past_line_boundary")

file load:
  cursor_line = 1
  first line is a drawing -> cursor_line = 2
click on text -> cursor moves
click on first character of text -> cursor on first character of text
click to right of text -> cursor past end of line
click to right of wrapped text -> cursor on final character of line
click on drawing -> cursor doesn't move
cursor past end of line -> renders
create drawing -> cursor bumps down below drawing
backspace
  cursor_pos == 0, previous line is a drawing -> delete drawing, cursor still visible at start of line
  cursor_pos == 0, previous line is text -> join lines, cursor still at same character

enter
  cursor_pos == 0 -> insert empty line above current line
scrolling:
  given moby dick, a file containing all text:
  page up moves top line on screen to bottom
  page down moves bottom line on screen to top
  cursor remains on screen
  cursor remains on text line
  'up' arrow with cursor at top of screen scrolls up one line (drawings still fully in or out)
    if cursor line wrapped before, it scrolls up by only one screen line
    if previous line (above top of screen) wrapped, it scrolls up by only one screen line
  'down' arrow with cursor at bottom of screen scrolls down one line (drawings still fully in or out)
    if cursor line wrapped before, it scrolls down by only one screen line

clipboard:
  cut/copy without making a selection