check_eq(App.filesystem['foo'], 'abc\ndef\n', 'check')
end
  check_eq(#Editor_state.lines, 3, '#lines')
  check_eq(Editor_state.lines[1].data, 'abc', 'lines:1')
  check_eq(Editor_state.lines[2].data, 'def', 'lines:2')
  check_eq(Editor_state.lines[3].data, 'ghi', 'lines:3')
  edit.draw(Editor_state)
  check_eq(App.screen.width, 200, 'width')
  check_eq(App.screen.height, 400, 'height')
  check_eq(Editor_state.left, Margin_left, 'left_margin')
  check_eq(Editor_state.right, 200-Margin_right, 'right_margin')
  check_eq(Editor_state.width, 200-Margin_left-Margin_right, 'drawing_width')
  -- TODO: how to make assertions about when App.update got past the early exit?
end
  check_eq(App.screen.width, 300, 'baseline/width')
  check_eq(App.screen.height, 300, 'baseline/height')
  check_eq(Editor_state.left, Test_margin_left, 'baseline/left_margin')
  check_eq(Editor_state.right, 300 - Test_margin_right, 'baseline/left_margin')
  App.resize(200, 400)
  -- ugly; resize switches to real, non-test margins

  edit.draw(Editor_state, Text_color)

  check_eq(#Editor_state.lines, 1, '#lines')
  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 1, 'cursor:pos')
  check_eq(Editor_state.screen_top1.line, 1, 'screen_top:line')
  check_eq(Editor_state.screen_top1.pos, 1, 'screen_top:pos')

  -- click on the other line
  edit.draw(Editor_state, Text_color)
  edit.run_after_mouse_click(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
  -- cursor moves
  check_eq(Editor_state.cursor1.line, 1, 'F - test_click_with_mouse/cursor:line')
  check_nil(Editor_state.selection1.line, 'F - test_click_with_mouse/selection is empty to avoid perturbing future edits')

  check_eq(Editor_state.cursor1.line, 1, 'cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'cursor:pos')
  check_nil(Editor_state.selection1.line, 'selection:line')
  check_nil(Editor_state.selection1.pos, 'selection:pos')

  Editor_state.selection1 = {}
  edit.draw(Editor_state, Text_color)  -- populate line_cache.starty for each line Editor_state.line_cache
  edit.run_after_mouse_release(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)

  -- selection is empty to avoid perturbing future edits

end
function test_move_cursor_using_mouse()
  io.write('\ntest_move_cursor_using_mouse')
  App.screen.init{width=50, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc', 'def', 'xyz'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  Editor_state.selection1 = {}
  edit.draw(Editor_state, Text_color)  -- populate line_cache.starty for each line Editor_state.line_cache
  edit.run_after_mouse_release(Editor_state, Editor_state.left+8,Editor_state.top+5, 1)
  check_eq(Editor_state.cursor1.line, 1, 'F - test_move_cursor_using_mouse/cursor:line')
  check_eq(Editor_state.cursor1.pos, 2, 'F - test_move_cursor_using_mouse/cursor:pos')
  check_nil(Editor_state.selection1.line, 'F - test_move_cursor_using_mouse/selection:line')
  check_nil(Editor_state.selection1.pos, 'F - test_move_cursor_using_mouse/selection:pos')

-- Most apps can just use the default (https://love2d.org/wiki/love.run), but
-- we need to override it to install a test harness.

    local status, err = xpcall(_G[name], handle_error_in_test)

  App = saved_app

function handle_error_in_test(err)
  local full_error = debug.traceback('Error: '..err, --[[stack frame]]3):gsub('\n[^\n]+$', '')
  table.insert(Test_errors, full_error..'\n')

-- prepend file/line/test
function prepend_debug_info_to_test_failure(test_name, err)
  local err_without_line_number = err:gsub('^[^:]*:[^:]*: ', '')
  local stack_trace = debug.traceback('', --[[stack frame]]5)
  local file_and_line_number = stack_trace:gsub('stack traceback:\n', ''):gsub(': .*', '')
  local full_error = file_and_line_number..':'..test_name..' -- '..err_without_line_number
  table.insert(Test_errors, full_error)
end

end