support running tests multiple times

We now collect multiple test failures, but that's just the first step.

app.lua

@@ -12,11 +12,68 @@
 -- Scroll below this function for more details.
 function love.run()
   App.snapshot_love()
+  -- have LÖVE delegate all handlers to App if they exist
+  for name in pairs(love.handlers) do
+    if App[name] then
+      love.handlers[name] = App[name]
+    end
+  end
+
+  -- Stash current state of App for tests
+  App_for_tests = {}
+  for k,v in pairs(App) do
+    App_for_tests[k] = v
+  end
+  -- there's one nested table
+  App_for_tests.screen = {}
+  for k,v in pairs(App.screen) do
+    App_for_tests.screen[k] = v
+  end
+  -- Mutate App for the real app
+  -- disable test methods
+  App.screen.init = nil
+  App.filesystem = nil
+  App.time = nil
+  App.run_after_textinput = nil
+  App.run_after_keychord = nil
+  App.keypress = nil
+  App.keyrelease = nil
+  App.run_after_mouse_click = nil
+  App.run_after_mouse_press = nil
+  App.run_after_mouse_release = nil
+  App.fake_keys_pressed = nil
+  App.fake_key_press = nil
+  App.fake_key_release = nil
+  App.fake_mouse_state = nil
+  App.fake_mouse_press = nil
+  App.fake_mouse_release = nil
+  -- dispatch some methods to real hardware
+  App.screen.resize = love.window.setMode
+  App.screen.size = love.window.getMode
+  App.screen.move = love.window.setPosition
+  App.screen.position = love.window.getPosition
+  App.screen.print = love.graphics.print
+  App.newText = love.graphics.newText
+  App.screen.draw = love.graphics.draw
+  App.width = function(text) return text:getWidth() end
+  App.open_for_reading = function(filename) return io.open(filename, 'r') end
+  App.open_for_writing = function(filename) return io.open(filename, 'w') end
+  App.getTime = love.timer.getTime
+  App.getClipboardText = love.system.getClipboardText
+  App.setClipboardText = love.system.setClipboardText
+  App.modifier_down = love.keyboard.isDown
+  App.mouse_move = love.mouse.setPosition
+  App.mouse_down = love.mouse.isDown
+  App.mouse_x = love.mouse.getX
+  App.mouse_y = love.mouse.getY
+
   -- Tests always run at the start.
   App.run_tests()
+  -- example handler
+  if #Test_errors > 0 then
+    error('\n\n'..table.concat(Test_errors, '\n'))
+  end
 
---?   print('==')
-  App.disable_tests()
   App.initialize_globals()
   App.initialize(love.arg.parseGameArguments(arg), arg)
 
@@ -369,63 +426,18 @@ function App.run_tests()
     end
   end
   table.sort(sorted_names)
+  local saved_app = App
+  App = App_for_tests
+  Test_errors = {}
   for _,name in ipairs(sorted_names) do
     App.initialize_for_test()
-    _G[name]()
+    local status, err = xpcall(_G[name], handle_error_in_test)
   end
   print()
-  -- clean up all test methods
-  for _,name in ipairs(sorted_names) do
-    _G[name] = nil
-  end
+  App = saved_app
 end
 
--- call this once all tests are run
--- can't run any tests after this
-function App.disable_tests()
-  -- have LÖVE delegate all handlers to App if they exist
-  for name in pairs(love.handlers) do
-    if App[name] then
-      love.handlers[name] = App[name]
-    end
-  end
-
-  -- test methods are disallowed outside tests
-  App.run_tests = nil
-  App.disable_tests = nil
-  App.screen.init = nil
-  App.filesystem = nil
-  App.time = nil
-  App.run_after_textinput = nil
-  App.run_after_keychord = nil
-  App.keypress = nil
-  App.keyrelease = nil
-  App.run_after_mouse_click = nil
-  App.run_after_mouse_press = nil
-  App.run_after_mouse_release = nil
-  App.fake_keys_pressed = nil
-  App.fake_key_press = nil
-  App.fake_key_release = nil
-  App.fake_mouse_state = nil
-  App.fake_mouse_press = nil
-  App.fake_mouse_release = nil
-  -- other methods dispatch to real hardware
-  App.screen.resize = love.window.setMode
-  App.screen.size = love.window.getMode
-  App.screen.move = love.window.setPosition
-  App.screen.position = love.window.getPosition
-  App.screen.print = love.graphics.print
-  App.newText = love.graphics.newText
-  App.screen.draw = love.graphics.draw
-  App.width = function(text) return text:getWidth() end
-  App.open_for_reading = function(filename) return io.open(filename, 'r') end
-  App.open_for_writing = function(filename) return io.open(filename, 'w') end
-  App.getTime = love.timer.getTime
-  App.getClipboardText = love.system.getClipboardText
-  App.setClipboardText = love.system.setClipboardText
-  App.modifier_down = love.keyboard.isDown
-  App.mouse_move = love.mouse.setPosition
-  App.mouse_down = love.mouse.isDown
-  App.mouse_x = love.mouse.getX
-  App.mouse_y = love.mouse.getY
+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')
 end